I'm going to give you a lecture on,
let's say, two objects that will
accompany you throughout your personal
and professional life from now on and
besides also since the past, which
are called energy and climate change.
So I'm not an academic.
My job is to be a consultant.
I am a partner in a consulting firm.
I have a second job as President of an association.
And I do extension work
that eventually led to this course.
That's why I do this job rather than my
main job.
The course I'm going to give you is
essentially a course based on
observational data, relatively simple
reasoning with hands.
I hope it will be accessible.
It is not very different (to be very frank)
from a number of things that I
can tell in other forums for audiences
that have not been carefully selected
through contests.
So, normally you should be able to keep up.
I'm still going to remind you of a
couple of little things as an appetizer.
The first is that you will remember
much more easily what I say if you take
notes (even if you trash them afterwards)
rather than if you don't take them.
So it's a very good mnemonic way to take notes.
The second thing is that I will try in
particular to invite you to always
approach problems by reasoning by
orders of magnitude and rules of 3. 
You have entered this school having been
carefully selected for your
above-average ability to solve
complicated problems that are well-posed. 
All right?
You have been selected to enter this
school for solving problems that are
univocal: they have only one solution.
Perhaps a little complicated,
but they have only one solution,
and they are well-posed.
That is to say, in the problem, you
have all the information you need to
find the solution. 
Life and what I'm going to tell you
from now on, is essentially made up of
ill-posed problems where you don't have
all the information. All right?
And when we approach a problem that is
ill-posed and that we do not have all
the information, there is something
that is extremely effective in
addressing these problems -- and it
will be particularly true in what I am
going to tell you -- it is to reason by
orders of magnitude and rules of 3.
And everywhere in your life, if a
sophisticated model is not in line
with a well-established rule of 3, it
is because the model is wrong!
So here are some elements that I give
you as a preamble to the course that we
will have the pleasure of going through
together.
This is one of the most famous
pensioners in France.
He is retired because he would have
said he was going to stop working, but
that must not be entirely true because
from time to time, we see him do things
that are less fun than that. 
It doesn't matter.
So we're going to get him back in a
little bit of service.
When you ask a question in the
Millionaire Game, for those of you who
have already watched this excellent
game, you know that you are given 4
answers in advance. 
That is, you are told : “Here is the
student sitting there in the second
row, does he have a shirt a) blue,
b) green, c) yellow, d) black” and all
those who were currently sleeping are failing,
the others have the right answer.
Now, we will imagine that he asks a
question in an open way, that is, he
asks you: “What is energy?”
You know that in France there is a
Minister of Energy so you could ask
him: “What is energy?”
Normally, he should know since he is
the Minister of Energy.
Well, you would realize, if you asked
the question (I'll give you an example
in a few minutes), that in fact, the
first answer that comes to the bulk of
the population, I mean the bulk of the
population, so I'm not talking about
the world in which you live on a daily
basis.
It's this. 
That is, if you say “energy” in a
number of forums and in particular in a
forum that we call “general public”;
the first thing that will come to mind
for many people -- and in fact it is
normal because it is something that is
also the first way to present energy in
the world of economists -- is that it is
something that is bought: a convenience.
It's a thing to buy and so the main
subject is whether it's expensive or
cheap, and if we could do it
differently to get the same thing for
less expensive.
This is particularly true in the news
since for all of you who have followed
this kind of movement, you know that it
started with a dispute over fuel prices.
So, of course, that is not the main
issue at the end of the day, but it
started with this dispute, which was a
dispute over fuel prices. 
So, the Yellow Vests never said: “We
don't want to consume fuel because it's
too much CO2” or “We don't want to
consume fuel because it makes us
dependent on Russia, Norway and we
don't want to.”
No, no.
They were just saying: “It's too
expensive.”
All right? 
So what I'm going to try to explain to
you during part of the rest of this
course is that, if you look at the
problem from that perspective,
unfortunately, you're missing the
point. 
There are several reasons why we are
missing the point. 
The first is that if you look in
strictly economic terms what it costs
to buy energy in relation to what you
earn. 
And you can represent it in several
ways. 
One of the ways I represent it, is to
look at what it costs to buy each year
from the whole economy, to buy the oil,
gas and coal that made it work. 
So, I look at the whole economic
product of the year and I look, in
relation to this economic product, what
it costs to buy on the market all the
oil we consume in the year, all the gas
we consume in the year (I speak for the
world as a whole) and all the coal we
consume in the year. 
Well, the result I get is that it costs
a few percent of what we earn. 
A few percent of what we earn.
I will show you a graph in a short
while on how much it costs the French
to buy energy and I assure you that to
pay Free, SFR or Orange (sorry I didn't
name anyone) to say: “Hello, I'm late”
or “Where are you?”
It costs roughly the same price. About
the same price.
It costs a few percent of what we earn. 
And from the moment an object placed in
an economic debate represents a few %
of the debate, well, at that moment,
the normal reflex will be to say: “I
will take care of it a few % of the time.”
And typically, what you see right now
in political debates is: I'm interested
in energy at election time a few
percent of the time and then, the rest
of the time, I give this to someone to
whom I delegate the problem by telling
them: “Make sure that this thing is
managed in your own corner, it's not
really my problem.
I do not see the link with pensions,
diplomacy, economic policy or the
number of printers in the country. 
There is no connection.
So I will consider it a subject that
can be detached from the rest and only
requires a few percent of my time.”
What I'm going to tell you from now on
is that this reasoning is as relevant
as if I told you: “Your brain is 2% of
your weight, so I can remove it from
you, it's not very serious, you'll lose
2% in efficiency.”
So, “pie chart” reasoning (and that's
something that's broader than just
energy) “pie chart” reasonings never
tell you if the “pie pieces” are
enslaved to each other or not.
There is another funny reasoning of the
same type which is to say:
“Agriculture is 2% of GDP so we don't
care, we can dump it, it doesn't matter much.”
Well, yes, except that if you stop
eating, the remaining 98% of GDP, quite
quickly, will be problematic.
So, the “pie chart” reasonings, you
always have to be very wary of the fact
that it doesn't represent the
dependence you can have on one “piece
of pie” to another. 
And what I'm going to show you now is
that, in fact, the dependence of the 97
or 98 or 95% of GDP that are not energy
purchases, in fact, is totally 100%
dependent in the modern world on the 5%
in question. 
So, energy is not an invoice, even if…
Well, objectively, it is not just an
invoice even if that is how we reason
in the economic world in which we live. 
There is another thought that often
comes to mind when we talk about
energy.
It's people telling you: “Ah, energy,
good energy, that's the energy we save.”
So, the second thing I'm going to show
you during this course is that if
you're in this room right now with the
time, at your choice, to sleep for
those who take a nap or to listen,
instead of being picking potatoes, it's
precisely because the World has been
increasingly consuming energy over the
past two centuries. [Sorry.]
So, in fact, the result of the world we
live in today is a world of growing
energy abundance and not at all a world
of growing energy savings.
So, in fact, the right energy, in the
sense of the one that allowed the
emergence of the industrial
civilization in which we live, is
precisely the one that we have not
saved.
The third topic that is very popular at
the moment is that: “Energy is not
very serious to know what it is. 
What is important is that it will
become 100% renewable.”
You will see that, in fact, that is not
exactly how it happened. 
And, in fact, the right way to approach
energy could be the poet's. 
That is, energy is what you are filled with
on a morning when you are in good
shape (or an afternoon, it depends on
when you get up). Well, in fact, this
way of seeing things is the right way
because, when you consider that you are
full of energy, in fact what it means
is that you consider you have a great
ability to control your destiny.
“I have a lot of energy, I'm very fit”,
that means, basically, “there's not much
I am afraid of”,
and so, “I have a great ability to
control my destiny”. 
But energy, as we will see from now on,
is that, having a lot of it, is precisely
having a great ability to control your
environment. 
It's that by definition.
By definition, having a lot of energy
means having a great ability to control
your environment. 
And why is that?
Because energy, before being an invoice
or before being a subject of debate, is
a physical quantity. 
So you know it well because you have
done a little bit of physics to get
into this amphitheatre, energy is a
physical quantity. 
It's quite funny, moreover, because in
physics there is no totally univocal
definition of energy.
I'll suggest one for you. 
For me, energy is what quantifies the
change of state of a system. 
All right?
Energy is what quantifies, I mean
quantifies, calculates, the change of
state of a system. 
In other words, the more the world
around you changes, the more energy has
come into play.
And, the more energy that comes into
play, the more the world around you
changes. 
It's as simple as that.
So if I take this back to
transformations in everyday life, here
are some of them, or more precisely
objects that transform the environment
in everyday life. 
These are objects that transform the
temperature. 
These are objects that are intended to
change a temperature, which I show you
here.
Either to heat or to cool down. 
And these objects use or eventually
release energy. 
Here are some objects to change a
velocity. 
That's all a car is for.
It is used to change the speed of what
is contained in the car, eventually you
and your luggage when you go on
holiday.
Well, a speed change is a change in the
state of a system.
Here are some objects to change a
shape.
You had soil, the soil is excavated, it
is placed next to the hole.
Change of form. 
You had a sheet metal, the sheet metal
is stamped and you have a car door. 
Change of form.
These machines use energy. 
You have energy that comes into play
when you change a chemical composition. 
And, by the way, the first chemical
composition that constantly changes to
provide energy in your immediate
universe is called your digestion of
the food you eat.
Actually, that's what they're for. 
They are used to provide you with
energy. 
You have energy that comes into play
when you have magnetic fields that
interact with electric currents.
So, it can either consume it, in an
engine, or “supply it”, in an
alternator. 
You have energy that comes into play
when you rearrange the nucleons of a
nucleus.
And you know the sun spends its time
doing that.
It is a large permanent thermonuclear
bomb that spends its time assembling
hydrogen nuclei to make helium nuclei. 
You have energy that comes into play
when you have material-radiation
interactions.
So, the interaction of matter and
radiation that interests you the most
is your smartphone. 
But in the end, there is more to it
than that in the interaction of matter
and radiation.
One that will be of great interest to
you, and to me too in a month and a
half represented by this young woman on
the right.
So, in a general way, using energy is
nothing more than transforming the
world around us and conversely,
transforming the world around us
necessarily implies that there is
energy involved.
So, once I told you that, a first small
remark.
Man is in transition. 
You know that we currently have a
Ministry of Energy Transition and not
just a Ministry of Energy.
We have a Ministry of Energy
Transition.
Well, the Ministry of Energy Transition
is probably the oldest Ministry in the
human community, since Men have been in
energy transition for 500,000 years.
500,000 years ago, the only energy that
humans could use was their bodily
energy. 
And then, they started to domesticate
the fire, so a first extracorporeal
energy.
In Antiquity, we started to domesticate
all renewable energies and, by the way,
even some fossil fuels. 
For example, oil was known to the
Sumerians, coal was known to the
Chinese a few thousand years ago, so in
small doses all this. 
And in fact, the industrial revolution
was the domestication of fossil fuels,
we will come back to that.
And so, the energy transition is a
permanent state of human beings.
Every time they find a way to use a new
energy source, they do it.
What characterizes the modern era (and
you will see that it characterizes it
extremely strongly and that is what
poses a problem) is that we have
radically changed the order of
magnitude in all these processes in a
very, very short time. 
So energy, as I told you, is a physical
quantity. 
From the moment I said that energy is a
physical quantity, it means that there is
every chance that energy will be
governed by laws that we cannot change. 
That's the charm of the laws of
physics. 
It's that you can understand what
Maxwell's equations are, but once you
understand them, you can't change them.
You can't say: “Well, it would be nice
for the purchasing power of consumers
if we could change Maxwell's equations
a little bit.”
No need to try. 
Well, as far as energy is concerned,
you have a few laws that
apply to us and that cannot be changed.
So, it is not to say that we do not try
to change them from time to time
implicitly by votes in the National
Assembly, but, nevertheless, it is
better to know them. 
So, as I told you, energy is what
quantifies the transformation of the
environment.
The first cardinal law that is very
simple to keep in mind when it comes to
energy and that you all know by heart,
of course, is the first principle of
thermodynamics or energy conservation
law.
So, the energy conservation law
applied to humans has a consequence
that is simplistic, which is that
humans can do nothing more than extract
from the environment an energy that
already exists and use it for their
benefit. 
That's all Men are capable of doing.
If Men were able to make energy appear
within them without communicating with
the outside, we would be violating the
first principle of thermodynamics.
So, I'm sure that in a good Harry
Potter, you can do that, but in the
real world it's more difficult... 
So, any energy we use, we have to find
it in the environment. 
Everything.
An energy that is in the environment is
called “primary energy” in the jargon
of energy experts. 
All right?
So when you see the term “primary
energy” passing through the statistics
(which I may ask you to look at)
 it means that it is energy as it
is found in the environment. 
There is another term that is very
common in energy (we will come back to
it in a few classes) which is
the “final energy”.  
The final energy is the energy that
passes the final consumer's meter. 
So, who is the final consumer?
It is you when you are at home and you
have a gas meter or an electricity
meter or you have an oil tank (it's
very bad, you can't tell anyone) and a
meter on the truck that delivers the
fuel or when you are an industrial, you
have a meter because you use gas in a
glass furnace.
There you go. 
So, as soon as you are an end consumer,
individual or industrial and you buy
energy that will allow you to operate a
machine, it is called final energy. 
The energy found in the environment is
called primary and in between, you
obviously have the energy system.
So historically, the only primary
energies that humans know how to use
are food and the warmth of the sun. 
There are two of them, I should have
put the heat of the sun on too. 
So, historically, the only converter
that people have at their disposal is
themselves.
Because, to use energy, you need a
converter.
We have to get this into something that
will transform it.
So, the only converter that people have
is themselves.
So, they eat, they heat themselves in
the sun and from these energies that
they absorb or ingest, it comes out
heat, a lot, work, a little.
And then, over time, we started to be
able to domesticate other converters.
So, apart from wood, a very rustic
converter, we started to domesticate
all possible renewable energies. 
So, at the time, renewable energies
included other living organisms,
because they were completely renewable.
Draught animals are perfectly
renewable.
It eats perfectly renewable grass and
therefore provides you with perfectly
renewable energy. 
Wind and water were also domesticated
through the mills. 
Ancient Europe was covered with water
and then windmills. 
And so, it must be clear that renewable
energies are not the future, they are
the past.
So not in the sense that there is
nothing to expect from the future.
What I mean is that renewable energies
were part of our daily lives a few
centuries ago. 
So, a world 100% renewable energy, I
know very well what it looks like. 
I have at least one sampling point,
it's the world three centuries ago. 
This one is 100% renewable energy, it
works very well. 
So, a world with 1 billion people on
Earth, 30-40 years of life expectancy
at birth and two thirds of the
population in the fields, that, I know
it works in 100% renewable energy.
There is no problem, since we did it
once.
Obviously, the debate today is: “Can
we achieve civilization with the
engineers at MinesParisTech and all the
machines we use today with 100%
renewable energy?”
So, we'll come back to that later.
And then, two centuries ago, there were
a few brilliant engineers and
physicists who said: “We could use
other converters, converters that are
non-renewable, in this case machines
made of metal, and we will give them an
energy that we do not yet know how to
use on a large scale today, called
fossil fuels.”
So here, I summarize for you in one
sheet what has been the energetic
history of men.
First the converter is us. 
Then it's other living organisms.
There were slaves in it too. 
Then, renewable energies and,
ultimately, metal machines with fossil
fuels.
And so, what I'm telling you also is
something that's absolutely essential
is that, in fact, we don't consume
energy, except what you eat.
So, when you see “energy consumption”
somewhere, it's an inappropriate term.
Because unless I'm mistaken, I don't
think you've ever drunk oil.
If anyone has ever done this here, let
them tell me, but normally not.
I don't think you've ever eaten coal
except the one used for flatulence.
And you didn't breathe gas, at least
not methane, the one that gives
Mickey's voice maybe. 
So, we don't consume energy with our
own bodies. 
In fact, when we say that we consume
energy, it is an inappropriate term --
but it is an inappropriate term that
induces an optical illusion that is
extremely strong.
Consuming energy is actually
domesticating a machine.
So, wherever you are going to see
“energy consumption”, including in my
slides – because from time to time I
use this shortcut even if I try not to
You replace by “using machines”.
And wherever you see that we are
“consuming more and more energy”, you
cross over and replace it with: “We
are using more and more machines”.
That's what you have to understand.
And in fact, the increasing amount of
energy we use is nothing more than how
to increase proportionally the huge
mechanical exoskeleton we have created
for our profit.
It's this, energy.
And this world of machines is the world
in which you live.
So, unless I'm mistaken too: moral and
weather conditions make you come to
this class dressed. 
If you are dressed, it means that you
have put on a piece of clothing at one
time or another.
So, putting on a piece of clothing
takes exactly a few seconds, even if
you are extremely clumsy. 
In the dark, badly awake, after the
ingestion of substances that I will not
name, perhaps a few tens of seconds but
never much more. 
A few seconds, then.
Well, in a matter of seconds you have
mobilized thousands of machines for
your benefit without realizing it. 
You have mobilized thousands of
machines for your benefit. 
You started by mobilizing all these
agricultural machines for your benefit
if you have a so-called natural textile
garment: cotton, linen, etc. 
You started by mobilizing all the
agricultural machinery that sowed,
harvested and eventually processed
cotton for your benefit. 
You have, if you use a synthetic
textile fiber (so everything that is
poly-whatever, nylon-thing,
all this comes from oil). 
So, if you put on an underwear that has
synthetic fibers or a t-shirt that has
synthetic fibers, well, you have put on
a piece of oil platform plus a piece of
steam cracker plus a piece of refinery,
those little 5 billion-dollar beasts
right there that you see in that
picture. 
If you have something other than an
unbleached fabric, it has been dyed, so
it was necessary to make the dyes.
So, you have the chemical industry that
has worked upstream, then you have
machines that have.... 
Sorry, we had to weave the fibers
first, excuse me. 
So, these are mechanical machines
again. 
It had to be dyed, so this is the
chemical industry. 
It had to be transported because
obviously it is not where you grow the
cotton that you weave it, that you dye
it, etc. 
So, you have other machines that have
been involved at all the intermediate
stages of the chain called trucks,
trains, planes. 
It was necessary to manufacture boxes
in which refineries were installed, in
which chemical plants were installed,
etc. 
So, you also have these machines that
have come into action. 
It was necessary for power plants to
supply part of the process. 
So, these machines also came into
action. 
In short, in something totally trivial
that we do as we breathe – that is
called putting on a garment --, well,
you don't realize it but there is an
army of machines that have worked for
you, just with this very simple
gesture.
So, after you get dressed, those who
have proper hygiene will brush their
teeth after breakfast. 
Again, it's the same: brushing your
teeth is something that takes three
minutes if you follow the doctor's
advice, one minute if you're in a
hurry.
You have again used considerable
quantities of machines simply to make
this gesture. 
You have here a picture of a chemical
factory in northern France that belongs
to the Roquet family group and that
produces a sugar that is found in
toothpaste, called sorbitol.
Then you know that sugar causes
cavities.
So, if you put sugar in your toothpaste
that causes cavities, it's still a bit
of a stretch. 
So, it turns out that the sugar we want
in the toothpaste -- so that it tastes
a little nice -- is a sugar that does
not cause cavities. 
It's a different molecule and, in fact,
it's one of the few hundred molecules
you're going to take out of a factory
called a starch factory, into which you
put a full train of wagons loaded with
corn every day and you take out
hundreds of different chemicals.
And, on site, there are a few thousand
people working on a plant that runs in
3/8. 
It is one of the largest chemical
plants in France. 
Then you have your tube that is made of
plastic. 
Now there are no longer really any
metal tubes. 
So, in plastic!
New oil platform / refinery / steam
cracker / etc.
And your plastic tube, it does not
appear by the operation of the Holy
Spirit from the plastic. 
You need an extruder, that you see
here. 
You brush your teeth in front of a
mirror because otherwise you do stains
everywhere.
So, we had to make the mirror. 
Here you have a train-float that makes
the mirror and, again, you need boxes,
trucks, etc.
And then you brush your teeth with
purified water and this is a water
purifying device, for example. 
So, again, an army of machines that
have worked for a daily gesture called
brushing their teeth.
Now, I come to the most important thing
in your life: your phone.
Well, it's the same thing. 
When you make a phone call, you have
mobilized an army of machines for your
benefit.
It was necessary to manufacture
plastics for the telephone, to
manufacture purified water, etc. 
Steel must be manufactured for antenna
supports. 
You have 40 different metals in a
smartphone. 
40!
Some present at extremely low
concentrations and several tens.
So, there are as many mining activities
here and there, so there are as many
mining machines, etc. 
Let's take the telecom network, that
makes possible to operate the 
– because if you're the only one with a
smartphone and others don't, it's not
much use,
you have to be able to communicate with
others.
So, we need a network. 
Here is for example a machine to run
cables to make the network, etc.
So, making a phone call is also
something that will involve thousands
of machines for all the intermediate
stages of construction and operation of
the device.
So, I say it again. 
Today, we live in a world of machines
and all these machines without
exception use energy.
All of them! 
And you understand well, to reverse the
reasoning I showed you earlier on: It
doesn’t matter if it's 3%: if you
instantly deprive the world of energy,
it's not 3% of GDP you're going to
lose... 
It's quite simple to understand.
You no longer have a means of transport
that works.
You no longer have banks, no water
networks, no hospitals, no transport of
any kind because no energy. 
All right.
So, you will starve, you will freeze to
death and you will kill each other.
Basically, that's what happens if
tomorrow morning, instantly, we deprive
the world of energy. 
So, the whole modern world depends on
it and that it costs 1% or 100% of what
you earn is not so much the subject.
Well, it's a subject, but it's not the
only one.
From now on, we will look at a number
of quantitative elements.
So how do we count energy? 
You know that when you are given an
exercise to enter to MinesParisTech,
generally the unit you are allowed and
the only one is the Joule. 
I'm not going to use it much because if
I expressed in Joules the quantities
we're going to discuss from now on,
there would be so many 0’s on the slide
that you'd take too long to look at it.
So often we'll use units of energy a
little different from the Joules
because it avoids Gigas and Megas and
it allows us to have smaller things.
So, already the first way to remove 6
zeros in Joules, is to switch to
kilowatt-hours (kWh). 
And the advantage of the kilowatt-hour
is that it is what appears on the bills
(even if energy is not just a bill).
It also brings us closer to things that
are more familiar in everyday
discussions. 
A French individual today uses, all
uses included, imports included (i.e.
including the energy that has been used
outside France to operate the machines
that supply his consumption in France –
because, to take the example of your
smartphone, from now on, it is “made
elsewhere” in its entirety), 
well, it is around 60,000 kWh a year.
As for energy companies, they have a
unit that they also like, which still
allows them to gain 4 zeros, which is
the ton of oil equivalent.
The ton of oil equivalent has a very
simple definition:
it is the equivalent of the energy
released by the combustion of one ton
of oil. 
So, a ton of oil does not always have
the same combustion energy, it depends
on the nature of the oil.
That's why we usually add “average
quality” and it's worth about 11600
kWh. 
From time to time, you will also have
units in the energy that are brought in
by the Anglo-Saxons, especially the
Americans; and you know that American
units are rarely compatible with the
metric system. 
There you go.
So, the ton of oil equivalent is part
of that big whole.
OK.
I'll use a little bit of the electron-volt.
Not often. 
And finally, I will also use
the “slave equivalent”.
So, the “slave equivalent” is about
100 kilowatt-hours of mechanical energy
and I will explain why right now.
Who has done this before in this
amphitheatre?
Oh, not more? 
Well, who has already walked up the
Eiffel Tower? 
Well, that's better already.
So, let's imagine that for some reasons
that interest you, you decide to climb
the Eiffel Tower 6.3 times during the
day.
Who has already climbed the Eiffel
Tower 6.3 times?
Ah, that's good. 
It's to impress the Japanese or...
No, it's for another reason? 
So, if you climb the Eiffel Tower 6.3
times during the day, with the Eiffel
Tower at just over 300 m, you will
experience a difference in altitude of
around 2000 m during the day.
In doing so, you will generally use
your legs since using your arms is
harder... 
Well, the mechanical energy that you
are going to release with an effort of
this nature (which is not a totally
marginal effort for everybody)
is E = m*g*h.
So, it's extremely simple. 
Well, actually, it gives a ridiculous
half a kilowatt-hour over a day. 
So, a man at work who uses his legs to
power any mechanical device like
Charlton Heston who pedals in “Green
Sun”, at the end of the day, he will
have been able to restore or provide
about half a kilowatt-hour of
mechanical energy.
If you imagine that this man at work
makes this effort every two days.
Which is another way of saying that you
climb the Eiffel Tower three times
every morning. 
Well, by the end of the year, your legs
will have provided about a hundred
kilowatt-hours of mechanical energy.
So, over a year's work, the carcass of
a reasonably trained man is capable of
providing about a hundred
kilowatt-hours of mechanical energy if
he uses his legs. 
If you use your arms (and let's say by
passing a little bit of back also and a
shovel -- it's more difficult with bare
hands), and that you pour six cubic
meters of soil, that is to say about 15
tons of soil in a day, 
well, in addition to blisters, you will
have provided 0.05 kWh of mechanical
energy.
That is to say, you are even “ten
times more ridiculous” than the person
who climbed the Eiffel Tower three
times with his legs.
So, a pair of arms at work during the
day is 0.05 kWh, a pair of arms at work
during the year is about 10 kWh of
mechanical energy.
If you burn a liter of petrol, that
costs the scandalously high price of
1.60 € (which justifies finding it too expensive)
you're going to get 10 kWh of thermal
energy. 
And if you want to have a strict
comparison, obviously you have to put
it into a machine that will convert
this thermal energy into mechanical
energy; even with the best engineers in
the world to make cars, you will get 2
to 4 kWh of mechanical energy, no more.
It doesn't depend on the engineer, the
2 to 4, it actually depends on how the
car functions
(if it is close to its optimal
performance or not). 
Well, so if it's 2, it's the driver's
fault, it's not yours. 
So, you will get 2 to 4 kWh of
mechanical energy. 
That is to say, in a single liter of
petrol (which we will see in a short
time that the French still consume not
far from 1000 liters per year), you
have the same work content, the same
capacity to change environment, as in
10 to 100 days of hard work by a human
being. 
I am telling you again
when you use a machine that consumes a
liter of gasoline, you are able to
change the environment, that is to
provide work, at the same level as 10
to 100 human beings who would use
either their legs or their arms.
I don't know if you realize the
difference you have between the energy
we use through the machine and our own
body.
If we convert all this into money,
another way of saying the same thing is
that the kWh of mechanical energy, if I
pay a man at work to provide it, I will
pay him from a few hundred to a few
thousand euros, while the machine at
work provides me the same service for a
marginal cost (I did not put the
machine in there) in the order of a few
tens of cents.
So, when I go from man to work to
machine to work, outside the cost of
the machine, I divided the cost of a
unitary transformation of the
environment by a factor of a few
hundreds to a few thousands.
The reason why we are mechanizing
everything we can in the economic world
is there. 
So as soon as you can replace a worker
with a robot, you do it. 
As soon as you can replace a worker
assembler on a chain with a robot, you
do it.
As soon as you can mechanize anything,
a farmer, replace it with a tractor,
you will always, always, always, always
do it, because of this absolutely
considerable difference in price
between human labour and energy.
That is why we have always been looking
for effective machines to replace
people with machines. 
It even worked for the replacement of
slaves. 
If you take a slave, which is usually
not a youthful vocation… 
Well, this slave, to make him work,
you're going to have to go get him
against his will.
You have to pay money. 
I would remind you that there was a
time when there was a slave trade that
was a completely immoral business by
current standards, but in the meantime,
it was still done for economic reasons.
You have to stop him from killing you,
you have to stop him from getting out
of here, you have to feed him and so
on...
And when you look at what it costs to
get a slave's work, you realize that
even that, it will cost you 10 to 100
times more than the machine that has
nothing against its condition as
machines, that does not seek to get out
of the way and that does not go on
strike and works 24h/24.
So, the reason why slavery has
disappeared in societies that have had
access to energy is not because the
genetic code has changed.
So, I'm going to make a little
incursion into the course you didn't go
to for some of you: it's not because
our genetic code has changed.
Our genetic code is exactly the same as
that of our ancestors two or three
centuries ago. 
Simply, there are no longer any
incentives to do things that we were
doing at the time because we found much
better and much less annoying to do the
same thing.
So, what freed the slaves was oil.
At this stage, there are some initial
conclusions that I propose to you. 
So, I remind you that using energy
implies that energy already exists in
the environment.
So, sometimes in a debate, you see
people telling you: “We could use
hydrogen.” 
Hydrogen in the environment, there is a
place where there is a lot of it, it's
called the sun.
It's not very convenient to pick it up. 
The rest, it is everywhere in bound
form. 
In water, there is plenty of it.
You have a lot of it in life, etc.
But everywhere, it is in bound form, so it
is not available as an energy source. 
The molecule is available, the energy
is not. 
You have to break the bonds, so for
example electrolyze water and for that
you need more energy than the energy
you get from hydrogen combustion. 
So, hydrogen is not a primary energy
source. 
When you are told: “We could use the
fuel cell.”
Well, it's an engine. The fuel cell is
not an energy source. 
So, what we have to compare to the
primary energies we use today is other
primary energies, i.e. things that can
be found in the environment and that
are usable as they are in the
environment. 
The rest is not accessible.
As energy quantifies transformation,
you have no “green energy” (or, by
the way, no “pink energy” and no
“black energy”).
In fact, choosing an energy means
choosing a type of transformation and
choosing advantages and counterparts. 
Any energy is dirty if you bring it to
a sufficient level of use. 
Any one of them.
The day you cover the entire planet
with photovoltaic panels, it stops
being clean. 
So, clean energy, in general, when you
look at the figures, you realize that
it is an energy that is used in
sufficiently small quantities that its
disadvantages are also small.
In general, this is a clean energy. 
As soon as energy begins to be used in
massive quantities, regardless of how
it is extracted from the environment,
there are disadvantages. 
And choosing an energy means choosing
between the disadvantages you want and
those you don't want.
That's the point. 
Something that is absolutely essential,
I will come back to it several times
during this first module of the course,
is that energy (I am not talking about
what makes it possible to extract it
from the environment) energy is free! 
So, you all heard, the wind is free,
the sun is free. 
So, there's no reason not to use it.
In fact, wind and sun are free, no one
in this room has paid a penny for the
sun to exist, for the wind to exist. 
But no one in this room paid a penny
for oil to exist either! 
Oil is free of charge.
What needs to be paid is the
willingness to share of the person who
is lucky enough to be sitting on it. 
That's what you pay for.
And what needs to be paid is the work
of the few of you who will go to Total
(it's very bad, don't tell anyone!) to
go make holes in the ground and bring
out the oil. 
That's what you pay for.
Oil is free of charge. 
It's free of charge.
So, when we pay for energy, all we pay
is human labor and human rents to
access energy that is free. 
We only pay men and the money is used
to pay only men. 
You've never seen nature send an
invoice to anyone. 
So, we only pay men.
As energy is physics, and as what you
pay for is not energy itself but
the work you have to dedicate to extract it
from the environment, the price of an
energy does not depend on the abundance
of energy (because you could say
“if the energy is very
abundant, it is thus even more free
than the others”). In fact, that is not
what matters.
If an energy is very abundant, it can
still be very difficult to extract from
the environment. 
You know, there is an energy that is
totally superabundant in the universe,
it's the 3 Kelvin degrees radiation in
the void. 
I can tell you that you will never do
anything with it, although there are
absolutely considerable quantities.
So, the fact that there are absolutely
considerable amounts of energy does not
tell us anything about how easy it is
to extract it and use it for our
benefit. 
What will count for the cost of energy,
i.e. the ease with which it can be
extracted and used for our benefit, is
the fact that the pre-existing energy
source in the environment is already
very concentrated and with few barriers
separating us from access to this
source. 
And so, the archetype of this thing is oil.
Oil is hyper-concentrated (less than
nuclear energy, but nuclear energy is
more complicated to use). 
It's very concentrated and the barriers
that separate us from its access are
not very hard to cross.
Historically, Mr. Drake went to Titus
City to make three holes and the oil
spilled. 
It's not very complicated historically
to get oil out. 
The more energy is separated from us by
large barriers and the more diffuse it
is, the more expensive it will be to
extract from the environment. 
It's just physics.
And then I'll show it to you with a
quick comparison.
Let's imagine that I take the volume of
air in this room, which is not very far
from representing a cube of 10 m on
each side.
Let's imagine that I blow it at 80
km/h, which is either a good mistral
for the southerners, or 45 knots of
wind for the sailors.
And I'm running this through a wind
turbine.
If I put this wind through a wind
turbine, it will put this wind mill in action and
provide me with electricity. 
This electricity is an energy, I can
count it. 
Well, the amount of electricity I
recover with a thousand cubic meters of
air at 80 km/h that passes through the
wind turbine is the same as the amount
of energy I recover by burning 3 ml of
oil, 3! 
Not 3 tons, not 3 liters, not 30
liters: 3 milliliters, 3
mini-milliliters.
With regard to the amount of human work
to invest, in your opinion, is it
easier to go and make a hole in the
Saudi desert and bring out 3 ml of oil
or is it easier to build a wind
turbine, wait for the wind to blow and
recover the electricity that comes out? 
Well, the answer is in the prices.
Since money only pays men. 
If you use a wind turbine, in Europe,
you will pay 6 to 8 cents  for your kilowatt-hour of
electricity (for the wind turbine part)
and at that price, there is class
when there is wind.
When there is no wind, the video
projector does not work.
Well then, I can yell a little loud,
there's no microphone, it's okay.
I can do with my hands without a
projector, but for all of you who have
come by subway, there is no subway
either, it's a little more annoying.
There is also no party tonight if the
wind is not blowing.
This is starting to get really, really
annoying.
There's no alarm clock tomorrow morning
if it runs on electricity.
The fridge: you can't cool the beers,
well, it's a disaster.
So, if there is no wind, the system
stops.
If you don't want the system to stop
when there is no wind, you have to add
the cost of storage. 
And then, at that moment, you multiply
roughly by 3, sometimes by 6. 
So, the order of magnitude of the
kilowatt-hour stored with wind is a few
tens of cents.
In contrast, the order of magnitude of
the cost per kilowatt-hour already
stored (since when you take your oil
out of the ground it is already a
stock), 
at that time, you can already use it
today, tomorrow, the day after
tomorrow, next week, or at 3am, exactly
as you wish. 
Well, this kilowatt-hour of oil already
stored out of the Saudi desert is worth
0.3 cents.
So, between the cost of one
kilowatt-hour extracted and stored from
the wind
(diffuse source, the air is not dense:
1.2 kg per cubic meter, it's really not dense)
and the cost of a kilowatt-hour
coming out of a Saudi oil well
you have a
factor of about a hundred
on the cost of making available
a stored kilowatt-hour.
And again, there, the wind turbine, you
made it with oil.
The system is not closed-looped. 
That is to say, to manufacture the wind
turbine, you have benefited from a very
efficient industrial system that has
extracted the copper from the mine,
extracted the bauxite from the mine,
extracted the iron ore from the mine,
metallurgy upstream, assembled all this
stuff, transported, erected the
concrete block, etc.
All this was done with fossil fuels. 
If you had to do all this with other
wind turbines, it is not completely
certain that the price of the wind
turbine would always be 6 to 8 cents
per kilowatt-hour.
We can take the bets. 
My bet is that it would be worth a
little more. 
So even if you do the wind turbine with
fossil fuels, you realize that you have
a factor of a few tens to a hundred
between a kWh out of the wind and a kWh
out of an easy oil well.
And that's irremediable because it's
physics.
So that's why historically we haven't
switched from fossil fuels to renewable
energy, but we have done the exact
opposite.
Two centuries ago the navy was 100%
renewable and moreover as the wind does
not always blow, it was necessary to
take lemons on board to be sure that
sailors did not catch scurvy. 
And it came to us that, to bring you
the Zara t-shirt quickly (because the
t-shirt is not made in France), it's
still much better to have a 100% fossil
navy.
It's much more efficient. 
It goes a lot faster.
We had a 100% renewable transport
system a few centuries ago and we
thought that, nevertheless, to supply
the Ecole des Mines for lunch, it's not
terrific, it's much better to have 100%
fossil transport, it works better.
We had a 100% renewable agriculture and
we thought that, nevertheless, to have
a very productive agriculture and for
farmers' children to go to school, it
is not terrific, it is much better to
have a 100% fossil agriculture.
We had 100% renewable civil engineering
-- that's how the Romans built the
Roman roads -- it wasn't very fast to
build a million kilometers of roads in
France, it's still much faster to use 
We had a 100% renewable construction
industry. 
A century to build Notre-Dame.
So now it's going to go a little faster
to rebuild the roof.
And probably a few centuries to build
the pyramids: it wasn't very effective.
To build Tower D2 at La Défense, it's
much better to use fossil fuels, it
goes much faster. 
We had a 100% renewable industry.
Again, it wasn't very effective making
all the objects you have on you, at low
cost: it doesn't work well. 
It is still much better to have a 100%
fossil industry. 
We had 100% renewable dryers, that is
to say the sun, and it is still not
very efficient: it is much better to
have dryers that run on gas, it goes
faster.
So, it's been two centuries. 
Precisely because the physical
characteristics of fossil fuels are
superior to the physical
characteristics of renewable energies,
that Man, who is an accumulative animal, has
spent his time switching from renewable
energies to fossil fuels, to be able to
accumulate faster. 
That's exactly why we went that way.
And so, when you see that, you tell
yourself that to go the other way, like
that, simply because the political
promise is that you will get there
without touching people's standard of
living, just by seeing that, you tell
yourself: “Oh, yeah? 
Oh, yeah?
Are we totally sure? 
Do I sign with all my savings plus
those of my parents plus those of my
grandparents, on the fact that it will work?”
Incidentally, when you have a doubt
about something, it's a very good
question to ask yourself.
That is: “Would I agree to bet all of
my parents' savings on what I am saying?”
There you go.
End of the parenthesis. 
If you have a very slight doubt that
the answer is not yes, it is because,
in essence, you are not totally
convinced by the argument or by what
one is telling you.
So, we know renewable energies very
well.
This is the world from which humanity
comes out.
So, I insist, I'm not saying we
shouldn't go back.
I'm just preparing you for the
conclusion that we're probably not
going to go back with constant
consumption.
Certainly not.
With 7 billion people on Earth...
So that's it, our converters of ancient
times, they were completely immoral,
and not at all effective. 
However, it was completely renewable.
And we have now moved on to modern-day
converters that are much more
efficient, no doubt about it. 
So, if I don't talk “energy” but talk
“power” now. 
Well, you see, a man at work whom I
told you earlier in a day's work, he
can do between 0.05 and 0.5 kWh.
If you relate that to 5 hours of work
(actually it's 10 but whatever), you
see that it means that his average
power over that time is somewhere
between 10 and 100 W.
Let's take a tractor.
An ordinary tractor today has a power
of a few tens of kilowatts (kW).
A tractor has the same power, by the
way, as a construction machine that
makes a hundred kilowatts. 
If, one day, you're a little curious,
the next time you pass by a
construction site
on all construction machinery, you have
a small plate that gives you the power
of the motor that is hidden somewhere
under the pivoting part.
Anyway, it's not very complicated to
locate
go check it out by curiosity,
you will see the power of the device:
a few tens of kilowatts up to 100 kW for
a large shovel.
If you substitute legs, a few hundred,
if you substitute arms, a few thousand.
So, the two machines you have here are
capable of replacing a few hundred
pairs of legs or a few dozen draught
animals with the tractor.
And, for civil engineering or
construction machinery, a few thousand
pairs of arms. 
It is thanks to this that we have been
able to increase a farmer's
productivity by a few hundred: because
he did not grew hundreds of arms and
hundreds of legs like in Shiva.
The farmer was simply given an
exoskeleton.
And it is thanks to this that, today,
we can build a house (that plus a whole
lot of other machines, cement
factories, trucks, etc.) that we can
build a house today for the cost of a
few years' salary: thing that was
totally unthinkable for an inhabitant
of ancient times.
Until two or three centuries ago, it
was just unthinkable that someone could
have their house built for a few years'
salary: it didn't exist.
A truck pedals like a few thousand
times the driver's legs.
A plane, thanks to the young and
handsome pilot who is well paid, pedals
like a million times on the pilot's
legs.
The “Aeroflot” one probably didn't
pedal hard enough.
An industrial rolling mill hammers and
crushes the steel like the whole of the
Île de France to whom I would have
given a hammer.
So, you see. 
Just to replace the Fos-sur-Mer rolling
mill, if we didn't have any energy, you
wouldn't be listening to this course
right now, you'd be hitting metal sheets with
a hammer.
Just to replace the rolling mill in
Fos-sur-Mer.
The whole of Île-de-France with a
hammer, hammering all day long.
This is another agricultural auxiliary
that has saved a few million pairs of arms:
it's called a steam cracker, and
it's something that helps you prepare
organic chemistry.
At this point, we agree that energy
quantifies transformation. 
On the fact that, to use energy, you
actually need a converter. 
On the fact that most of the converters
we use today are no longer our own
bodies but are machines.
And now I will quantify the number of
machines and how they are broken down
by individual. 
So, I told you, historically, what we
were using was mainly renewable energy. 
So here you have a graph that starts in
1860 and quantifies only one of the
renewable energies that we have used
since ancient times -- because for wind
and water, it is difficult to have
statistics in long series. 
I'm sure someone would be able to
reconstruct that, but I didn't find it. 
So now we're already going to start
with the wood. 
So, wood, a century and a half ago, was
used by humanity.
Humanity uses it to feed stoves, to
heat itself, to feed forges. 
And, by the way, the beginning of
metallurgy has been a massive factor in
deforestation or a very important
factor in deforestation in Europe. 
And to operate the first steam engines
that are about to emerge here and
there.
At that time, an inhabitant of the
world, an earthling, consumes an
average of 5000 kWh of wood per year. 
So, you see that, per person, since
that time, the amount of wood used has
decreased.
Not in total, but per person it has
decreased.
It is roughly the only energy that
has followed this evolution.
After that, Men started using coal. 
So, some of the coal substituted
wood. 
For example, in Europe, we started
using coal. 
Before, we used charcoal and then we
started using so-called “bituminous coal”
(both called “coal”) to run the forges.
And then to run the steam engines.
And you see that the amount
of coal used per person in the world
that was extremely low a century and a
half ago is now about 5000 kWh per
person per year.
What you see on this graph as well is
that the amount of coal used per person
in the world has never decreased since
we started using coal.
So, never, at any time, has coal been
an energy of the past for Men.
Never, at any time. 
And in fact, today, you unknowingly use
a lot of coal through everything that
is imported from countries where it is
“made in coal”, starting with China. 
So as soon as you see something “made
in China”, it is “made in coal” and
it feeds your consumption, indirectly
of course, of coal. 
Two-thirds of the coal used on Earth
today are actually used by an
intermediate machine in the energy
system called the power plant. 
So, two thirds of the coal extracted on Earth
are used to power a power plant. 
In the rest, you have a roughly 10%
that feeds the metallurgy. 
So, they are coals very rich in carbon
that are called “coke coals” and
otherwise, the rest is used to operate
heating networks, stoves, district
heating and finally domestic heating, etc.
But two thirds of it are power plants.
You know that in France we have a great
debate on our nuclear power plants.
Remember that, today, in the world, you
have between 30 and 40 times, between
30 and 40 times, the nuclear power
installed in France in coal-fired power plants.
In France, we have 60 GW of nuclear power,
and about 2,000 GW of coal-fired
power plants installed worldwide.
We will come back to this at the time
of the climate course, but the Paris
agreement (rings a bell?)
and more exactly the 2ºC objective
contained in the Paris agreement
assumes, for example, that all these
coal-fired power plants have
disappeared by the time you are my age.
All right? 
So, three meters separate us.
So, by the time you're my age, not that
far away, I can assure you, all the
coal-fired power plants in the world
must have disappeared...
We're not really there yet...
Then, Men used oil.
So, what you see on this graph in an
absolutely spectacular way, is that oil
has never replaced coal. 
Oil has not replaced coal.
You can see that the use of oil per
person is added to the use of coal per
person. 
The reason is that oil is not used
for what coal is used for, not at all. 
Oil is the queen energy of mobility
because oil is the energy that has the
best ratio of energy transported per
unit volume. 
All right?
In a liter, so a cubic decimeter, if
you put something that you use for your
energy supply, there is nothing better
than oil.
It's liquid at room temperature, so
it's something that's extremely easy to
store and transport. 
And since it is the densest per unit
volume, well, in the modes of transport
where you have to take your energy with
you (so you are sure to be able to go
where you want) it is oil that has won
the battle of the modes of transport,
hands down.
Today, 98% of everything that rolls,
flies or sails uses oil.
While I remind you that, the first car
in the world to have exceeded 100 km/h
was an electric car. 
I would also remind you that the
efficiency of the electric motor is
four times higher, three to four times
higher than the efficiency of the oil
engine.
So, it is not because the oil engine is
intrinsically superior that it
supplanted the electric motor in the
competition that took place a century
ago: it is because with electricity you
have much more difficulty to take with
you the energy that allows you to be
autonomous.
That's the reason. 
You also see here something that happened
before you were born. 
The sudden stop, and I really mean
sudden, of the amount of oil available
per person on Earth.
This episode, it has a rather special
name in the history of energy.
It's called “oil shocks”. 
I will come back to this at length.
The oil shocks, everyone kept in mind
that it is a moment when the price
became very high, then it became very
low again, and “next subject please,
let's forget it”. 
In fact, we don't forget at all.
This is the moment when the oil supply
grew strongly and stopped growing
strongly; and when the oil supply per
person grew strongly and, not only
stopped growing, but then began to
decrease and stabilize.
So, oil shocks are not just a price
episode.
In fact, it's the foam on the surface
of the wave.
The major feature of the oil shock is
that it is the end of a rapidly
expanding world. 
These are the oil shocks and we will
soon come to what they mean in economic
terms.
The gas comes in. 
So, gas, bis repetita, has not replaced
oil. 
It came to be added on top of it.
Hydroelectricity comes along. 
Same thing, hydroelectricity was added
on top of that. 
Then comes the nuclear, which has been
added to it, and now arrive the new renewable
energies (that you see there)
which is THE thing that everyone is
talking about.
We talk about nothing but 
new renewable energies.
Here you have, brought down to the
individual, what these new renewable
energies represent in the world. 
And, as I am, despite appearances, a
nice guy, I took the nicest possible
conversion convention to account for them.
Because, as many of these energies are
purely electrical energies (solar and
wind) you have two ways to account for them.
Concerning electrical energy, you have
two ways of counting it in the energy
balances.
As historically most of the electricity
has been produced by thermal modes
(these are Carnot machines -- power
plants -- for the most part: you burn
coal, you burn gas, you burn oil, you
fission uranium, etc.) it produces heat
and with this heat, you operate a
turbine.
It's a Carnot machine. 
In a Carnot machine you have a maximum
efficiency (1-T2/T1) and often,
electricity is counted in primary
equivalent i.e. we count the thermal
energy that would have been necessary
to make the same amount of electricity
for the modes that are purely electric,
hydropower in the lead, solar and wind. 
And that's the convention I used for
this graph. 
Nevertheless, you can see that today,
it is something that has much more
space in the newspaper's pagination
than it does in the actual consumption
of energy in the world; and you will
soon see that not only is it true in
absolute terms, but unfortunately it is
also true in terms of dynamics. 
On the other hand, another thing that
is crucial when you see this graph, is
that today, the amount of energy
mobilized per person per year
(extracorporeal energy I should specify)
is about 20,000 kWh. 
So, on average, an earthling mobilizes
20,000 kWh per year through the
enormous exoskeleton of the machine park.
With the little equivalence I gave you earlier...
So that's primary energy, that's thermal energy.
So, in mechanical energy
it would obviously be less, but
in this case, you're going to replace
legs, but you're also going to
replace arms, so I used a rough
one-for-one convention. So, I'm telling you:
it's as if, basically, each
earthling had 200 people at his
disposal: 200 slaves who would work for
him all the time. 
I will tell it differently: the
machinery we have built up and that
works for us has the same mechanical
strength as if our muscle power were
multiplied by 200.
So, you are, I am, we are, we have
become Superman for real.
It's not a matter of the mind. 
Except that, contrary to Popeye
devouring boxes of spinach and becoming
super-powerful, we devour barrels of
oil and become super-powerful. 
Well, not us, but our exoskeleton, i.e.
the machines. 
I'll tell it again in a different way.
The material production of humanity
today at 7 billion people is equivalent
in volume, because of the machines, to
what we would have if we had
1400 billion people and no machines. 
Is that clear?
Obviously, we cannot afford to feed
1400 billion people on Earth.
So, in fact, thanks to energy and
machines, we have been able to develop
a productive capacity that is beyond
the muscular power of our body and we
spend our day using prostheses. 
The train that brings me here is a
prosthesis. 
It's an extension of my legs.
The car you may use, and the plane even
more so, are prostheses.
They're extensions of our legs. 
Okay, we spend our time using
prostheses. 
Most of this energy is fossil fuel.
Then why “fossil”? 
Simply because they are remnants of
ancient life. 
A fossil is very simple once again.
It has a definition: it's a remnant of
ancient life.
We will see it at the next class,
coal is a remnant of plant life
(ferns that grew in the Carboniferous era)
and oil and gas are remnants of
plankton and microalgae that lived
anytime between a few million years ago
and a few hundred million years ago. 
So, it is fossil energy by far that
dominates the global supply today. 
And this energy, it has therefore made
it possible to set in motion a growing
exoskeleton that has made each of you
Ironman for real. 
So, we all became Ironman for real.
We don't have the little light shining
in the center and the things in front
of our eyes there, but that's exactly it.
So here are some little bits of your
Ironman costume and mine: washing
machines, elevators, vacuum cleaners,
tractors, Ariane rockets, satellites,
water purifiers, rolling mills, etc. 
All these are little bits of your
Ironman costume. 
And without this Ironman costume, you
would have the life that French farmers
had a few centuries ago with 30 years
of life expectancy at birth, no
increase in income between birth and death...
The idea that income increases with age
is something that is modern: it didn't
exist in ancient times.
So, what has literally changed the
lives of humanity is the energy and the
machinery that makes it possible to use it.
That's why the fact that it's only
worth 3% of what we spend is an optical
illusion! 
It's at the center of 100% of what
happens to you. 
100%!
In fact, with the little economic
convention I showed you earlier,
the energy today and the machinery it
operates is 200 times the muscle power
of Men. 
If the accounting were to be consistent
with this physical reality, in
companies' accounts, energy would be
worth 200 times more than wages. 
That's what should happen.
So, your hiring salary should be
roughly divided by a factor of 1000.
Roughly. 
That is about what we should do if we
were to have the same accounting
balance on costs as we have the
physical balance on the contribution to
the transformation of the world.
I'll tell it another way because I'll
get to it in a little while: today,
people in production are only needed to
operate machines.
For the rest, they are useless. 
So most of the jobs we do today in the
world, I cut off your 2 arms, your 2
legs, and I allow you to order a
computer with your brain, it still
works.
It still works. 
So, this exoskeleton, with its own
energy, allows it to have the same
productive capacity, so on average
worldwide it is 200 the factor, but on
average in France it is rather 600.
So, the French Yellow Vest who doesn't
realize it (and that's the unspeakable
political truth) still lives like a
nabob.
He lives like a nabob. 
So, what pisses him off is that Bernard
Arnault lives even more like a nabob
than he does (and he's probably right
to think so), but in the meantime, he
himself already lives like a nabob.
Because of that. 
These modern-day slaves have another
absolutely considerable advantage over
the renewable energies of ancient
times: it is that they free up the
entire surface for us.
Because the energy slaves of ancient
times, either renewable energies or
other living organisms that were
needed, mobilized soil.
A draught animal mobilizes soil. 
Therefore, the soil that is necessary
to feed the draught animal is no longer
available to feed Men or a transport
animal. 
At the time, therefore, there was a
particular need in agriculture to
mobilize a large part of the land in
order to be able to cultivate the rest
of the land for humans, with draught
animals. 
There, the slaves of modern times, they
eat from the underground. 
So, they leave all the available space
to us. 
And that is one of the reasons why,
when we talk about returning to
renewable energies, you see land use
conflicts appear. 
For example, to grow crops for energy
purposes, it directly conflicts with
food crops.
So, in fact, it means that we are
obliged, for part of the energy we use,
to return to the ground compared to the
advantage we had of just hitting the
underground. 
So, we are returning to a
two-dimensional system, whereas we had
succeeded in moving to a
three-dimensional system. 
In a way.
Some orders of magnitude of common
energy usages.
This thing is very old but the order of
magnitude is still valid.
There's probably a dividing factor of 2
that's been running around for some of
them, but that's okay, it's just for
fixing your ideas.
What you see then, all that I can
translate into “slave-days”, which I
did. 
Above all, remember from this graph
that most of the energy consumption of
a Westerner, and therefore the machines
he uses for his benefit, is not light
and is not recyclable coffee cups.
So, since I am going to talk to
engineers who are supposed to
manipulate orders of magnitude: it is
not with small gestures that we avoid
big problems. 
We can have small actions to start tackling the
big problems, but that doesn't replace
tackling the big problem.
So, I say this because in the world in
which I live, which is the business
world, it is still very, very often
that we confuse orders of
magnitude, deliberately! 
You hide behind your little finger and
say “Look! It's fabulous, I put a hive
on the roof, I put recyclable cups in
the canteen, and then one day per year
people will come by bike and...”
No, it doesn't work that way. 
Obviously. So here you have some orders
of magnitude of energy consumptions. 
You see that something that will weigh
very, very heavy, is what you buy and
how you move around.
When we talk about climate change, we
will also see that the way we eat is
something significant, and the way we
lodge.
So, basically, the size of the
accommodation you occupy, the energy
you use to occupy it, the amount of
stuff you buy in the year and the way
you travel and the number of kilometers
you drive in the year, is much more
impacting than turning off the light or
not when you leave a room.
It is not at all the same order of
magnitude.
So, at the same time as, per person
(because until now I talked in “per
person”) the orders of magnitude have
fundamentally changed.
The size of the population has also
fundamentally changed.
You have here a reconstruction
(approximative obviously because ten
thousand years ago INSEE was a little
less efficient than today)
you have an approximate reconstruction
of the human population.
Then why ten thousand years ago? 
Why does this graph start ten thousand
years ago?
It is the sedentarization of Men.
That is, ten thousand years ago
(and we'll see about that in the climate
change course)
we get out of the last ice age,
we are at the beginning of the warm
interglacial era, which is the one we
knew until we started to initiate
human-induced climate change.
This means a period of very strong
climate stability that allows people to
settle down. 
That is to say, in a stable climate,
the resource that allows you to feed
yourself does not move around because
it moves with the changing climate. 
It always stays in the same place so
you can start settling down. 
At that time, there are a few million
humans on Earth. 
Again, INSEE was not very successful at
that time. 
At the beginning of the industrial
revolution – I recall the life
expectancy at birth of the inhabitants
of Earth in 1800: it is a little less than 30 years.
By the way, it was less in the
city than in the countryside because
at the time, cities were a place where
miasmas of all kinds were concentrated
and therefore as soon as there was a
disease, it was much easier to catch it
and die from it than when you were in
the countryside. 
You also had the same thing for infant
mortality... 
And there are 1 billion of us.
And, what you see is that in the time
frame of two centuries, we have
experienced an evolution that is closer
to hyperbolic than exponential, at the
same time as the quantity of resources
of all kinds consumed per individual
has also increased. 
So, in fact, some of the people I know,
including myself, are wondering whether
this demographic change would have
taken place if we had not had abundant
energy.
Because if we had not had abundant
energy, it is not completely certain
that cereal yields would have increased
from 10 to 80 quintals/hectare in
Ile-de-France. 
It is not entirely certain that food
could have been transported wherever it
is needed from where it grows.
It is not completely certain that we
would have been able to protect it from
the hot, cold and all the little
animals that want to eat it in our
place. 
It is not completely certain that we
could have brought drinking water and
evacuated the miasmas from cities, etc.
And so, there are a lot of things that
are not completely certain in a world
where we would not have had fossil
energy, and so it is not completely
certain that we would have grown to 7
or 8 billion people.
And if the question arises as to
whether 7 or 8 billion people is not a
consequence of abundant energy, then
obviously, at that moment, the
corollary question arises: from the
moment we enter a strong energy
decline, do we stay at 8 billion
people?
It's not completely certain either. 
If I make “population times individual
use” this is what I obtain
regarding the total amount of energy
used by Men. 
That is, basically, the evolution of
the machinery park, knowing that
between here and there it takes much
less energy to run a machine, because
your predecessors and mine were astute
on how to run the machines, and
therefore gained in efficiency.
So, what you are seeing here is a lower
bound of the number of machines in
operation around the world. 
So, in my opinion, here we are close to
the machinery park, and this is more
like one-tenth of the machinery park in
operation in the world. 
What you see is that, between my
parents' generation and my children's
generation, the amount of energy used
by Men has increased by a small factor
of 10 and, in my opinion, with the
energy efficiency gain that there has
been in the same period of time, the
number of machines in operation in the
world has increased by a factor of a
few tens. 
It is not completely certain that the
same thing will happen between you and
your grandchildren's generation.
It's even pretty certain that it's not
going to happen.
So, it is quite certain that the world
you and I will know for the few decades
that I still have to live (if all goes
well) will not be a world of
prolongation of the trend we have had
in the past.
I remind you that physical systems are
exceptionally linear systems.
In general, they are non-linear
systems.
And that, in non-linear systems, you
cannot reason by induction.
It is better to avoid it. 
If I look at the mark of Man on his
environment. 
I can approximate it by the amount of
energy he uses since, I repeat, the
amount of energy we use is the flow of
transformation that we operate (by the
very definition of what energy is).
So, for that, I take the energy per
person times the population and it
gives me something that looks like the
evolution of the human print on its
environment. 
Well, here is the population.
I do “times energy used per person”
and this is in first approximation how
Man's print on his environment evolved
on a planet that was 13,000 kilometers
in diameter at that time, and still is
13,000 kilometers in diameter at that
time. 
And so, you understand that the
environmental problems we have today
are not necessarily problems that are
qualitatively different from what we
had in the past.
However, they are quantitatively
different from what we had in the past.
Today we have a tiny little problem of
order of magnitude.
And when you see that, you also
understand that we have put the system
out of balance (a tiny little bit) and that it
is not completely certain that it will
remain in that state for extremely
long.
So here I am preparing you for
something that I will detail in other
courses, which is: things will happen
anyway in the future, and anyway, in
the future, the world will not remain
stable.
Anyway. 
And, therefore, we have, you have, I
essentially have a choice between: I
wait for the instability to happen as
it wants to happen and I suffer it; or
I trigger the instability within the
limits of what I can still more or less
control.
But it will be one or the other. 
Two small additions on the evolution of
the amount of energy used in the world. 
Here you have the variation in the
amount of energy used by Men between
2000 and 2017.
And, what you see is that --
notwithstanding the media discourse on
the fact that it's really good because
we have more and more wind and solar
production -- 
what you see here is that the 3
energies that have increased the most
over the period (and by far) are the
three fossil fuels, and in particular
coal.
So, the fossil energy that has
increased the most since we started
having major debates on climate change,
is coal.
Coal, over this period, increased more
than ten times more than solar energy
(in primary equivalent) and more than
five times more than wind energy.
So, if the newspaper had a pagination
reflecting the facts, for an article
about solar energy, there should be 15
about coal.
All right? 
That's what should happen.
And if you look today at what you have
in terms of supply, so I'm pie charting
the historical evolution I showed you
just before, you see that it is fossil
fuels that dominate the global supply
with head and shoulders.
First, oil, then coal and gas. 
If I just look at renewable energies,
you see that what comes first is wood,
followed by hydroelectricity.
I would like to point out that the
first two terms of France's renewable
supply are the same two: wood and
hydroelectricity.
Just because the newspaper talks about
wind and solar power, again, doesn't
mean that it's what counts the most in
French renewable energy supply: it is
wood and hydropower by far, the other
terms afterwards being much, much
weaker. 
And so, here is the French renewable
supply. 
A little graph I made just yesterday
with statistics that were published no
later than two weeks ago.
What you see is that the first two
terms (by far) in the French renewable
supply are wood (which is mainly used
for heating) and hydroelectricity
(which is used to make electricity). 
Here you have wind and solar power.
You can see that solar energy is in
fact one of the weakest terms in the
French renewable energy supply behind
many other things, heat pumps, waste,
etc. 
Here are all these renewable energies
(so these are millions of tons of oil
equivalent, I told you that I would use
tons of oil equivalent) in a French
consumption that is about 250 with this
same unit. 
So, you see what renewable energies
represent in this whole. 
Now I'll let you go for five minutes.
Take the opportunity to chat a lot at
that time: but five minutes, not a
quarter of an hour. 
Thank you.
I'm going to go back to prices a little
bit now.
You have probably (for some of you)
heard (I will come back to this in the
next course but I will already give a
little overview today) that the price
of energy
(which can't be discussed in the last
row of this amphitheatre) 
must increase sharply if energy becomes
scarcer, which means that more abundant
energy should see its price fall
sharply. 
The price of all energies is in fact
more or less subject to the price of
oil.
So here you have the oil price
expressed in constant currency, i.e. in
a currency adjusted for inflation over
the past century and a half.
So, you see something quite
interesting: it is that this oil price,
in fact, on a long trend, there is a
century during which it was rigorously
stable (expressed in constant currency)
regardless of the quantity produced.
You see that at the moment of the oil
shock (characterized by a strong
variation of the derivative, i.e.
production rises rapidly and stops
rising rapidly) the price rises
sharply then returns more or less to
its previous level, then again you have
a shock where the price rises sharply
and returns to something that is not
very far from its previous level.
So the idea that the price of oil is
something that follows the abundance of
supply is not confirmed by this graph
that you see here.
On the other hand, the real price of
things -- in fact it is not the price
expressed in currency, it is the price
relative to the only magnitude that
remains incompressible over time, which
is the 24 hours of a day.
In other words, the real price of
anything is not the price expressed in
money, it is the price expressed in
minutes of working time.
If you want to express a price in
minutes of working time, it means that
you have to relate a price to what
people earn, and therefore in this case
you have to relate the price of oil to
what people earn, which is what you
see here, that is, the GDP per person. 
And then, at that moment, we fall back
on our feet. 
You see that over the past century and
a half, or over the past century, the
price of a barrel of oil has been
divided by 15 to 20, which means that
with the efficiency of machines, which
has increased at the same time, the
price of a kilowatt-hour of mechanical
energy has been divided by 50 to 100. 
We find the same dividing factor as the
one you have when we compare the price
of an old renewable energy with the
price of a modern fossil energy. 
We will always fall back on this
dividing factor or multiplier factor of
a few tens to a hundred, which also
represents the passage of a human being
producing with his arms and legs at 200
slave-equivalents per person. 
So, basically, no matter how you look
at the problem, the transition from
renewable civilization to fossil
civilization has been the appearance of
Superman or Ironman for each of us,
with a multiplication by an order of
magnitude of a hundred or several
hundreds of our capacity for action on
the environment.
And of course, as a result, all the
undesirable by-products of this ability
to act have also been multiplied by
several hundreds.
So, we have removed a lot of surface
area for other living things, which is
why there is a loss of biodiversity. 
We have induced a lot of pollutions of
all kinds in the environment. 
So, there are a whole bunch of
undesirable substances that have been
released in the environment as the
transformation flows have increased. 
This is a perfectly logical
consequence. 
If we look at a more recent period,
however, here you have the price of
energy in relation to what the French
earn. 
Well, you see that the Yellow Vests may
be right for their particular case. 
They are wrong for the population as a
whole because the price of energy in
relation to what people earn, as a
first approximation, has almost never
been as low as it is today.
So, when one says: “Aaaah! the liter of
gasoline at 1.50 €!”
OK. 
Except that we forget that people's pay
slips have increased proportionally and
even a little faster.
So, I've already said it implicitly. 
I will say it again more explicitly.
This abundant energy allows you to sit
in this amphitheatre today, and in
general, has radically changed the
world around us in terms of work and
professions. 
Almost all the people you know today
work in services, work in the city and
work in the service sector.
I mean almost everyone you know. 
This is a very recent situation that is
the consequence of the increase in
energy supply.
Here you have the evolution of the
number of employees in France, broken
down into: farmers in green, workers in
black, and service employees in blue.
These three curves cover two centuries. 
So, I'll just digress for a moment.
When you are interested in a process,
the longer the series you have, the
better. 
The best way to misinterpret a process
is to have a series that is too short
compared to the characteristic time
scales of variation of what you are
looking at.
So, you have to have sufficiently long
series if you want to understand
something. 
What you see is that two centuries ago,
two-thirds of the working population
worked in agriculture.
So, they are farmers. 
You also deduce one thing from that
case: if two-thirds of the working
population are in the fields, it is
because a farmer's productivity at that
time is enough to feed himself plus
half a person who does something else. 
That's what it means.
So, a farmer is feeding 1.5 people. 
And then you see that the number of
people in agriculture is increasing
slowly, slowly as well as the volume
until 1850. 
So, what's going on at the time?
At that time, you did not have a
significant increase in agricultural
productivity. 
Basically, an 1850 farmer is about as
productive as an 1800 farmer, a little
more but not much more.
On the other hand, what is happening is
that the population is increasing and
therefore, forests are being cut down
to increase the cultivated areas.
We are deforesting in Europe, just as
we are deforesting now in Latin America
or Southeast Asia. 
Just as we have done in the United
States and Russia. 
At all times, population growth has
meant that sedentary populations have
had to cut down forests to set up
cultivated areas instead. 
That is what the Europeans do, and
therefore the French, and so we cut
down forests until there is not much
left to cut down. 
That is to say, in 1850, we go through
the minimum forest level. 
15% of France is covered with forests,
no more. 
Today it's 25%.
And the 15% covered with forests are
essentially complicated areas to
cultivate, especially mountains. 
And then, the industry begins to
develop agricultural auxiliaries that
make the farmer more productive.
We start to develop trait collars, we
start to develop ploughs, etc.
It was the beginning of the forges and
industry that made it possible to
multiply the number of auxiliaries for
the farmer.
The first combine harvester in memory
was at the end of the 19th
century-beginning of the 20th century. 
It was pulled by horses at the time, of
course. 
And so, auxiliaries are brought to
farmers to reduce the number of farmers
and replace them with machines or
draught animals in the fields. 
At that moment, of course, it frees up
some people to do something else and it
feeds, but not only, the growth of the
workforce in other sectors. 
And then, after the war, this time
Ironman will arrive for real. 
You know that Ironman is an American
creation. 
It's Marvel's Comics.
Well, it's really the Americans. 
In this case, the Americans are
bringing the tractors and fertilizers
they had started to develop back home.
And we will replace human and animal
workforces with much more efficient
ones. 
That is, tractors and fertilizers.
Thanks to what, as I said earlier but I will repeat it
again: the cereal yield in Beauce, for
example, increased by a factor of 6 and
8 between 1945 and 1975.
6 to 8! 
I don't know if you realize that.
And at that moment, we can free up a
lot of pairs of arms and legs that are
in agriculture to send them elsewhere. 
So where do we send them somewhere
else? 
Well, we send them into the industry.
So, industry or craft is the same
thing.
So, in industry and crafts, we will be
able, thanks to the increasing energy
supply, to start up an increasing
quantity of machines and each time I
have a machine that starts up, I need
someone to drive it.
I have a car production line, I have
workers working on the line.
I have a jackhammer, I need a worker to
operate the jackhammer.
I have a crane, I need someone to
operate the crane.
So, more and more machines will be
built and it turns out that the energy
supply at that time -- we are at the
glorious thirty – you have seen the
speed at which oil per person is
increasing.
The energy supply at that time
increases faster per person than the
unit size of the machine. 
It's a horse race.
And so, despite the fact that I have
bigger and bigger machines, I can
create more and more jobs because the
flow, the machinery, basically, is
increasing. 
The machine fleet is increasing because
the unit size of the machine is
increasing at a slower rate than the
energy supply per person. 
So, I can increase the number of
machines and therefore increase the
number of jobs in the industry.
After the oil shocks, the opposite is
true.
The unit size of the machine continues
to increase while the energy supply per
person stops increasing. 
At that moment, I need fewer and fewer
people to drive machines that are also
getting bigger and bigger and will
continue to increase industrial
production.
Industrial production in France doubled
between 1974 and 2007.
So, after the oil shocks, we did not
de-industrialize ourselves, we made
another industry (fewer socks and more
planes), but what happened was that the
unit size of the machine continued to
increase even though the energy supply
per person stopped increasing. 
So, we reduced the number of employees
in the industry to operate machines
that were unitary larger and that
together produced more. 
But now, what I'm looking at is the
number of people, not the productive
power.
So, the number of people is decreasing
and we also have a second category of
jobs that is increasing, which are jobs
that are subjected to the industry.
So here too, something that is very
important to keep in mind is that
service jobs do not exist without
physical flows.
A service job as a teacher, for
example.
If you do not have physical flows to
make a teaching building, if you do not
have physical flows to bring students
and the teacher to the site, so means
of transport, if you do not have
physical flows to make teaching
materials, books in ancient times,
computers today, you do not have a
teaching system. 
Take a doctor.
A doctor, if you don't have enough
money to make drugs, medical equipment,
imaging equipment at the hospital, the
hospital itself and the transportation
to run all this, you don't have
doctors.
If you don't have a manufactured car,
you don't have a banker to do car
credit, you don't have an insurer to
insure cars, you don't have a driving
school instructor to learn to drive and
you don't have police officers to check
that people are driving well. 
All these jobs become useless in a
world in which you do not have the
underlying physical flow of
manufacturing cars. 
So, something you have to get out of
your head (and besides, I'm going to
show you the correlations showing that
you really have to get it out of your
head in a little while), is the idea
that a world rich in service jobs is a
dematerialized world.
It's the exact opposite. 
A world rich in service jobs is a world
in which there are a lot of flows to
manage and that's why you need a lot of
people to take care of it. 
So, service jobs increase as industrial
production increases because you have
to keep going, you have to manage, you
have to sell, you have to provide, you
have to teach, etc.
And you see that there is a period
where service jobs continue to increase
because industrial production continues
to increase while industrial jobs begin
to decline. 
On the other hand, from 2007, when
industrial production stops increasing
in Europe, we are also starting to have
a topic on service jobs. 
And you also see a new category emerge
that did not exist before the oil
shocks, namely the unemployed.
That is to say, the energy supply per
person overall no longer increasing,
the labour productivity does not
increase much since labour productivity
is the addition of machines. 
Labour productivity is increasing
little and existing jobs are too
productive for you to give everyone a
job in an economy that has stopped
growing rapidly.
In other words, from the oil shocks, we
are entering a time when the only way
to give everyone a job is to reduce
people's productivity at work.
And there, the equation is different
according to the different countries.
Some do not accept, and at that moment,
they create unemployed people: France.
Others accept, and at that moment, they
start creating poorly paid, poorly
qualified, odd jobs, part-time jobs, 
it is the more liberal systems:
England, Germany, America, etc.
But, it is one of the two possibilities
that is being set up. 
So that's the dynamic evolution in
France. 
Now I will show you some static or
dynamic developments that corroborate
what I just said.
Here you have a graph in which, with
the World Bank data, each point
represents a country. 
On the x-axis, I have the amount of
energy used per person, that is, the
average number of machines per person
in the country; and on the y-axis, I
have the fraction of the active
population working in agriculture. 
Well, you see, it's very simple.
It's: “Tell me how much energy there
is per person in the country and I'll
tell you what fraction of the working
population works in agriculture.”
All right? 
It's very simple.
Then, here is another graph that will
tell you the same thing.
Here, it is the evolution from 1991 to
2014 of two data in the world (so this
is the world average) 
it's the CO2 emissions per person (here)
and the fraction of the
working population in agriculture.
Well, you see that, the more CO2
emissions increase (which is the case
when you follow the chronological
order) and the more fossil energy you
have per person, the fewer farmers you
have in the active population.
So, it's true for the world but it's
true for India for example. But it's
true for China. And it's true for
Brazil. I have 250 countries in the
database, I'm not giving them all.
But it's something you see almost
everywhere.
So, you put energy into a country,
which means that you put machines in
the country, and you take farmers out
of agriculture.
And so you create a rural exodus. 
Everywhere the same.
Furthermore, the increase in agricultural
productivity has allowed us to increase
the quantity of animals we eat, since
we need more -- or more productive --
surfaces to eat animals that will
themselves need to eat what grows.
80% of what grows in France is used to
feed animals.
This is true for meadows, it is true
for all the corn except for the few
corns of the brands I will not name. 
And that's true for half of the wheat.
This is true for almost all of the
soybeans grown in the world, which is
one of the four major grains grown. 
So, roughly 80% of the cultivated land
in Western countries is used to feed
animals that you will eat afterwards.
And, what you see here -- so there I
didn't put the energy, I put the
greenhouse gases, it doesn't matter.
What you see is that in food-related
greenhouse gas emissions, where there
is meat or fish, you have a higher
hydrocarbon-related portion. 
And what you see is that the way of
History, because of the increasing
energy supply, is to go from left to
right. 
Historically, we ate cereals and
onions, that's why the farmers before
had stinky breaths.
Cereals and onions, and then we started
eating small animals.
First the product of the small animals:
the eggs; then the small animal itself
– remember Henry IV. 
People need to be able to eat small
animals: chicken in a pot for example. 
But chicken in the pot was already
garbage, because it has laid eggs all
its life.
It's an end-of-life waste, chicken. 
You eat the chicken.
Then we started eating broilers, then
we started eating pigs, then we started
eating cows. 
Being able to raise cows just to eat
them is something that is the hallmark
of a country under energy infusion.
It doesn't work… And the archetype is
the United States.
It doesn't work in a country with a low
energy supply.
And, because of the productivity
brought by the machines, this
increasingly meaty food costs us less
and less.
Here you have the share of food in the
household budget in the United States.
So it's a long series. 
I took
United States because it is easy to
find long series on American sites.
Despite the genius of French engineers,
finding long series of this nature in
three mouse clicks on a French site is
something very difficult.
I don't know why. 
But then, in any case, it works very
well in the United States. 
So in the United States, what you see
is that a small century ago, the
household food budget is a quarter of
what they earn and at the time it's
essentially home catering.
So, Mrs. Michu (sorry for this sexist
comment, but that's reality) buys raw
products from the local farmer or from
the local market and makes delicacies
for herself and Mr. Michu from leeks,
potatoes, eggs and chickens.
Today, when you go to buy food -- in
fact, most of what you buy (80% of the
French purchase food through
supermarkets),
most of what you buy is not food. 
The receipt at the exit of a
supermarket store is the salary of a
cashier, or the salary of engineers
from the company that made the
automatic payment terminals (it doesn't
matter), it's space rental, it's
warehouse salary, it's carrier salary,
it's Volvo Trucks' revenues, it's
Publicis' revenues, etc.
I mean, it's anything but food. 
When you look at the raw product in
what you buy,
in the good cases, it is one third of
the invoice. 
In the bad ones it's 3%.
Let's take the example of an egg box. 
How much does it cost to buy an egg box
in supermarkets? 
The bad ones, the non-organic ones.
No, these are the organic eggs that
cost 3 euros.
Yes, 1.5 euros, 
basically.
So, 1.5 euros for 6 eggs. 
So, since you're stronger than me at
mental arithmetic, it puts the egg at? 
It's hard: 15 divided by 6.
How many is that? 
That puts the egg at 25 cents.
We agree with that. 
Do you know how much the same egg is
bought off the farm? 
6-7 cents.
You can see that, just on an egg box -- zero processing,
zero processing -- you have a factor of
4 between leaving the farm and what you
pay at the cash register.
So, I insist, the receipt today is
anything but food.
This means that when you do a series
over a long period of time, you
actually have a massive inhomogeneity
between what you watch at the beginning
of the series and what you watch at the
end of the series.
Because at the beginning of the series,
it is really the egg as it comes out of
the farmer's house bought at the market
by Mrs Michu.
Today it's not that at all. 
And outside the home it's even worse.
The omelette at the local café, that's
not a 1.5 euros you're going to pay for it.
You're going to pay it 5 or 6 euros for
3 eggs, for 75 cents of egg. 
So you add a factor of 10.
So, in fact, the real price of food
today, it basically was divided by a
factor of 20 on this time scale, the
rest is service.
We encounter again the dividing factor
of a few tens.
So it varies according to the products,
thanks to the energy abundance.
This abundance of energy has also
brought us the means of transport.
Remember (without going into detail)
that the more modern a means of
transport is, the higher its
consumption per kilometer.
So we had bicycles, we had walking, we
had buses, we had trains, etc.
And then, today, we have the airplane,
the most energy-intensive mode of
transportation per person of all those
imaginable.
Once we had these extremely efficient
means of transportation, we also took
the opportunity to do something else
with them.
So, just a little parenthesis. 
In inhomogeneities, in long series, you
have another thing to see: it is that
over time some objects may no longer be
assigned only to their original
function.
Because a car today is not just a means
of transport.
It's also a living room on wheels. 
So it's your own space that you carry
to the office door. 
And that is also something that has
value and it is also an object of
status.
So I will also make a small aside on
the inhomogeneity of the series.
A car, when you compare it to something
else, sometimes it's hard to know what
it is compared with, and that's the
last avatar of the car.
This is the autonomous car “by IKEA”. 
Is that a car?
Is this a living room on wheels? 
Is it a computer on wheels that
transports you incidentally? 
What the hell is that thing?
The connected autonomous car. 
So from time to time, you also have
inhomogeneities that you have to be
careful about.
But to return to the primary purpose of
moving:
the more modern are the means, the more
they consume per kilometer.
What I am saying is that the car
consumes less fuel than the plane,
which is a more modern way. 
And, the car consumes more than the
train which is an older thing. 
And more than the bus which is also
older, the bus itself more than the
bicycle which is older, etc.
So, basically, the more modern a
vehicle is, the higher its consumption
per kilometer is, and in fact that's
what I represent here.
What you have here is a graph that
gives you the amount of energy used in
grams of oil equivalent. 
So, this, this or this is really oil per
passenger-kilometer. 
That's what you have here.
And you can see that, with time, it
rises.
That is to say, it is lower for the
train than for the bus, lower for the
bus than for the car, lower for the car
than for the plane.
And there you have the number of
traveler-kilometers traveled in the
year. 
So the surface gives you the amount of
energy that is allocated to each mode
of transport.
And so here you understand that it is
the road that today dominates the
transport that is carried out. 
And I repeat, therefore, the way of
History is to move from economical to
less economical means, because there
was more and more energy available per
person.
Who in this room has never flown
before?
Two, did I count it right or not? 
I would have asked the same question in
1950, I would have had to ask it the
other way around,
that is: “Who in this room has ever
flown?” And I probably would have had
two hands up. 
The plane is something that, today, in
your socio-professional category and in
your country, it is something that you
use as you breathe. 
It's extremely recent and, by the way,
when you will be about my age, it's not
entirely certain that it will always be
the case. 
It's extremely recent because it's
something that requires very, very
large amounts of energy.
Remember that a round trip from Paris
to New York is a very, very large oil
bathtub. 
It is 400 to 500 liters of oil per
person for one trip, which is about the
same as the annual consumption of
someone using their car. 
For one trip.
That's a lot. 
So, the opening of MinesParisTech
school to foreign countries (excuse me,
I have to live with my time) in 2060...
It is not completely out of the
question that it looks more like night
trains to go to Sweden than to
fly to Kuala Lumpur or China.
Or you will come back to the
semi-sailing boat to go to China, it
will take you a month, it will give you memories.
And you see here the way people move,
over two centuries.
And you have in logarithmic scale here
the number of kilometers driven per
person per day and there you have the
different means of transport.
So, you see, the horse was the one that
gave the most traveler-
kilometers per day (after the walk,
that is there in white) two centuries
ago. 
So, roughly two centuries ago, the
daily journey of a human being was 3 km
on foot.
(It wears out, it wears out...)
Because two centuries ago, as you saw
earlier, the ordinary human being was a
peasant and therefore he went back and
forth between the farm and the various
places where he needed to walk to do
his job. 
So its fields, orchards, meadows, etc.
That's what he was doing during the
day: 3 km.
And then, moreover, he lived all his
life without going a few hundred
kilometers away. 
Then you see: the horse.
Here you see the rise of the train and
then you see above all the rise of the
car, which has become the
dominant mode of transport today.
But the year when cars replaced walking
as the dominant mode of transport in
terms of passenger-kilometers per day
was the 1950s.
I was about to be born. 
My parents were born and well born.
So my parents, who were already born at
that time, were born in a world in
which the dominant mode of
transportation for the population as a
whole was walking. 
Also be aware of what this means in
relation to the world in which you
live.
We have reduced the number of farmers
and, as I said earlier, we have put
these farmers somewhere. 
So where do we conveniently make
industry and then tertiary jobs? 
In the cities.
Historically, what is a city? 
It is a place of exchange.
When you look at the cities that were
built a long time ago, they are all
organized around places of exchange
that are: the market place (I exchange
goods), the place of worship (I
exchange beliefs and moral rules) – so
the Church (to speak of France) is
always at the center --
the town hall or equivalent (I exchange
rules of living together), the school
(I exchange knowledge), etc. 
So, the places of exchange are at the
center and geometrically, the most
effective thing is a disk with everyone
around it, that's where it's most
compact.
The disk is the most compact shape. 
Around places of exchange which are all
placed in the center. 
Once you develop abundant means of
production and transport, at that
moment two phenomena will occur: 1) you
will empty the countryside. 
2) you will put people where it is most
efficient to produce and then exchange
production.
Where is it most efficient to produce
and exchange production?
In the cities. 
It is in cities that it is more
effective to do this. 
So you're going to put people in cities
and by increasing energy, so that's
what I'm getting at, you're increasing
the proportion of the population that
lives in cities.
So that's how it works for the world as
a whole.
In 1960 you have a little more than 30%
of the population living in the city
with three tons of CO2 per person,
which represents the fossil energy we
use, i.e. energy itself in a first
approximation.
And you see that today we are at 5
tons, so we have increased the energy.
This has made it possible to place
almost two thirds of the population in
cities. 
So, you see this evolution at an
accelerated speed in countries that
have had accelerated access to energy.
There is causality because you distort
the structure of employment.
And because a system in which you would
have left all the craftsmen, each in
their own corner with intermediate
transport, is much less efficient than
a system in which you put 100 craftsmen
together.
They are called workers, in a single
place that you will specialize for a
production and it will become very
efficient.
I'll put it another way. 
To make cars, if you have the 12-bolt
that is made in Brive and then the door
that is made in Aurillac and then the
door piece that is made in Bordeaux,
you can't get away with it.
So it's much easier to put everything
together in the same place and have
operations that are assembled in the
same place.
Then, when transport becomes more and
more accessible, you can go even
further in there and specialize even
more on certain operations, on certain
sites, since transport costs you
nothing.
And then you take them to other places
where, in mass, you hyperspecialize on
something else. 
That's why, for example, there is a
manufacturer who assembles his truck
cabins in a place other than where he
paints them. 
And in between, you carry unpainted
truck cabins. 
You have exactly the same evolution as
you can see in China. 
The same for Brazil, the same for
Thailand, the same for Indonesia, etc. 
More energy, I repeat, distorts the
structure of employment in the way I
mentioned earlier and the jobs that
appear are most effective if you
increase the size of cities.
So you can increase the size of cities
while spreading them out, and that's
exactly what happens when you have
access to abundant energy.
Because, at that moment, moving in
mechanized mode becomes easy and so you
try to do the best of both worlds. 
That is, a little space for everyone,
while having extremely important
exchange flows.
And that, you can only do that if you
have plenty of energy.
So in the energy-efficient city, the
most compact thing is the Haussmannian.
Paris is one of the densest cities in
the world despite the fact that there
are no very high towers. 
Because, when you have very high
towers, you have to start leaving a
little space around the towers.
It is complicated to tighten the very
high towers as you tighten the
Haussmann buildings that are stuck
together.
You have no space between the
buildings, they all face the street and
are all stuck together. 
With 10-storey or 30-storey towers,
it's more difficult to do that. 
And, on the other hand, it is the most
efficient mode when you don't have a
lot of energy to move around.
Because you can do everything on foot
or by horse cart.
When you give everyone a car, you go to
Los Angeles.
That is to say, you keep the same urban
functions of exchange by being able to
put the city in 100 or 150 km in
diameter with each having a car.
You keep the same distances covered in
one hour in a considerably more spread
out urban planning. 
So that's why, when you look at
Île-de-France for example: that's what
the distance between home and work
looks like, which is representative of
the daily exchanges in 1975.
So where it's white is that we don't
cover much distance.
So, in 1975, there you have a dense
city.
People walk to work. 
There you are still in the countryside,
people walk to go to their fields. 
And then, that's how it evolves over
time, and that's where we are in the
early 2000s.
All these people have become urban,
peri-urban people whose profession has
become an urban profession. 
They are no longer farmers.
They are employees of industry,
employees of services.
So they have entered into this travel
system that is necessary for industry
and services and they use their cars
because there is no public transit and
there will never be one. 
So you are starting to have extremely
long distances between home and work. 
By the way, where we're going to put
the Grand-Paris metro is in there. 
So, them, it will not solve their
problem at all. 
This abundant energy has also made it
possible to increase the housing stock
and it has made it possible to increase
it faster than the population. 
In 1900, then, let's say at the time of
the oil crises, the average housing in
France was 77 square meters and you had
a little less than three people in it. 
Today, you have a little more than two
people per dwelling! 
The housing itself having become
larger. 
So, obviously, it was energy that made
it possible to do that, and therefore,
energy allowed divorces in particular.
Because, to divorce, you have to have 2
dwellings where you only had one.
Otherwise it's not called a divorce. 
It's called domestic disputes, but it's
not called a divorce. 
Divorce is a physical separation.
You have to have enough to house
people.
And by the way, today, one of the
factors putting upward pressure on
housing needs in France is divorce. 
This is probably the first upward
pressure factor. 
You will find what I have just told you
in this little graph, which this time
gives you, for a given year, the CO2
emissions per person according to the
share of employment in services.
And, you can see that this graph says
everything except that when you
increase jobs in services, emissions
decrease proportionally.
It tells you everything but that. 
This is the only thing that cannot be
seen in this graph. 
So this is another way, this time in a
dynamic way, for the world as a whole. 
Again, you have the share of jobs in
services in 1991 and 2014 with CO2
emissions per person.
And you see that the two work together. 
And it works together again when you
look at countries taken one by one. 
It works very well.
Another evolution that abundant energy
has allowed is the increase in the flow
of goods since transport has also
applied to trucks.
There is also something we have to get
out of our brains, which is that we can
dematerialize transport by replacing it
with information flows.
Obviously, this is not true. 
When you look at the concomitant
evolution of information flows and
transport flows, whether it is goods or
people, you get exactly the same
result.
The two evolve together. 
So, today, on a macroscopic scale,
to say that to circulate more information would
allow us to circulate fewer people or
fewer goods, that is not true. 
That's not how it works.
Then, we can ask ourselves why it
doesn't work like that, but the gross
result is that it's not enough to
increase the amount of information that
circulates to say : “Well, the result
I'm going to get is that there are
fewer people moving or fewer goods
moving.”
Energy has therefore restructured the
country.
What I am presenting to you for France
has been applied in all the countries
that have had access to energy, all of
them.
You had populated countryside and not
too big cities.
You have moved to much larger cities
and empty countryside. And the cities
have spread out. 
And all countries have followed the
same trend. 
The only countries that have not
followed it are those that have had
geographical obstacles that have
opposed this development. 
So I'll give you an example.
Switzerland has indeed expanded its
cities.
It didn't spread them out much. 
Why?
Because when you have a city that is at
the bottom of a valley, spreading the
city out means climbing up the
hillsides, and it's complicated.
So they did it a little bit by putting
cottages everywhere, but they didn't do
it in a massive way. 
In particular, they did not make
hypermarkets on the outskirts of the
city because putting the hypermarket on
terraces at the top of the city is
more complicated than putting it on the
outskirts of the cities. 
So, the countries, once again, that
have not followed this evolution, it is
because they have had a physical
barrier that prevented them from
following it.
This abundant energy has also been
applied to leisure activities.
So leisure time has increased because,
like machines produce for us, it frees
us up time. 
So it frees up time for study.
At a time when there were no machines,
there were no long studies.
It frees up time for retirement. 
At a time when there was no abundant
energy, there was no pension. 
It frees us up time for the holidays.
It frees up time for us to do nothing
on weekends and it frees up time for us
to work only 35 hours a week. 
All the free time we have gained is due
to the abundant energy. 
So, here too, remember something that
will apply not only to you but to the
people you will work with and live with
for the rest of your life. 
In a world with limited energy, it is
not the increase in well-managed free
time that will apply.
What you see here is one of the
occupations of free time, called
tourism. 
And so, a few years ago, I did a little
calculation. I didn't do the
calculation again, but the order of
magnitude is still the same. 
It gives you the greenhouse gas
emissions, so again the consumption of
fossil fuels, linked to the way you
spend your holidays. 
So, in there I put in the initial
displacement. 
Going to the holiday destination by
train, car, plane. 
I have included the possible
manufacture of the object in which you
live during your holidays: the tent,
the caravan. 
The holiday home, I considered that if
we built it, I counted something, if it
was the old mother-in-law we had to
deal with, I didn't count anything
because she already had her house built
a long time ago. 
And then I also took into account local
travel if there are any, etc. 
If it is a skiing holiday, I have taken
into account the heating of the
apartment, since skiing is generally
complicated when it is very hot. 
It is rather cold and therefore the
apartments are heated, preferably with
fuel oil.
So I took all these things into
account.
And what you see is that the most
modern form of tourism (i.e. I'm going
to walk around the hotel for three days
by plane), is also the one that
involves the greatest amount of energy
consumed to afford a week's vacation.
Conversely, the first one, which are
the forms of leisure that appeared when
paid holidays appeared; that is, people
took their bicycles to go camping.
Or they would take the train to go
camping, that's what they did at first.
Here are the forms that are the most
economical in terms of fossil energy
-- and therefore in terms of energy alone --
to be used.
So, once again, energy abundance has
distorted our lifestyles.
And we owe the fact that we can benefit
from this leisure offer to the fact
that we are on an energy infusion, each
and everyone of us.
That's why Sweden has been developing,
for example, in recent years (it's been
in the media for a few weeks but in
fact when you look at the statistics,
it's a few years ago) a beginning of a
decrease in the number of planes taken
by Swedes that is now described by the
media as “Flygskam”.
So, it is because Scandinavians have a
rather more developed environmental
sensitivity than the rest of Europeans,
which can be explained by historical
and geographical reasons. 
We will find this again on the economic
level with what it costs in terms of
working hours to fly.
I'm telling you again, the real price
of things is the hours of working time.
And what you see, is that the price
expressed in hours of working time to
fly has been divided by an extremely
important factor in the space of a few
decades. 
This is another way of saying that
energy has become more abundant. 
That is to say, it is easier to pay for
a full amount of it with one hour of
working time.
It's the same way of saying it. 
Energy also drives industrial machines
and industrial machines will be used to
make all the objects that surround you
today. 
So, the tables on which you are leaning
for some, the chairs on which you are
all sitting, the clothes you are
wearing, the glasses for some, the
shoes, etc.
All this was made by industrial
machines.
So, the energy drives the industrial
machines.
So, it is the exoskeleton that makes it
possible to do everything, including
scissors, cosmetics and Netflix films. 
But it is also used as a raw material.
So you have a component in energy that
is sometimes called non-energy.
So you'll tell me: “The «non-energy»
in energy is still a little
complicated.” 
In fact, when you see non-energy uses
of energy, particularly oil and gas, it
is because it is used as a raw material
for organic chemistry. 
All organic chemistry is based on gas
and oil derivatives. 
So, there are Americans who have done a
funny little test. 
They have taken out of a house all the
products that contain petroleum
products.
Well, there's nothing left. 
In fact they also had to tear off the
floors because there is varnish on the
floors.
They should have ripped the curtains
off.
They should have ripped off the curtain
rod.
They should have removed the paint. 
I mean, they should have taken
everything off. 
So, oil today is not only something
that drives a machine, it is also the
basis of organic chemistry to produce
all the products that surround us. 
Because you don't have (more or less) a
single product that surrounds you in
which you don't have oil derivatives.
These objects that surround us, we have
to make them.
After, some of them will also use
energy.
Here, for example, you have the
evolution of the rate of household
appliances. 
So, I didn't find a more recent series,
the equipment rates have increased
considerably everywhere.
But you don't have a single household
today in which you don't have a fridge,
washing machine, etc. 
You have a whole bunch of things that
use energy. 
So industry makes things and it
requires energy. 
And after, these objects (some of
them), we will use them (up to the
lawnmower, etc.).
And it's also going to use energy. 
And you see that equipment rates are
increasing roughly everywhere and all
the time.
I already told you, I'm telling you
again: divorce is energy-consuming.
Because when you divorce, you have to
double the housing, so you double the
energy consumption of the housing. 
More precisely, you increase it in
proportion to the new area occupied. 
You need to build more homes, which
uses energy. 
You need to furnish twice as many
homes. 
So there are things you don't really
double, but there are things you
double.
For example, you have twice as many
beds.
Everyone sleeps in a bed. 
You have twice as many sinks, twice as
many hobs,  twice as many etc. 
And all that, you have to make it.
When there are children (this is not
always the case)
when there are children, they must then
be brought from one home to another.
This requires additional travel,
sometimes quite long.
As I told you earlier, a number of
things that are considered normal
today, so I'm repeating once again
retirement, studies, etc.,
it's energy. 
When Mitterrand, in 1981, said:
“Everyone must go to university” --
which was the implicit promise that
afterwards everyone would have an
office job
it was another way of saying: “I
promise you the society of infinite
abundant energy”, since I showed you
earlier that everyone in an office is
an extremely energy-intensive society. 
So at the time, when Mitterrand said
“Everyone must go to university”, in
fact he made the implicit promise that
we would be able to live in a world of
machines for eternity.
That is the implicit promise he made. 
So you see that energy is not at all
detachable from a whole bunch of things
even and including, the way we consider
access to competence. 
The hospital is also very energy
consuming. 
In France, hospitals account for about
5% of the country's carbon footprint. 
So as a famous comedian put it: if it
is the elderly that use the most health
services, all you have to do is remove
the last year of life. 
In the meantime, it still raises the
question of how long in a world of
constrained energy we can continue to
arbitrate in favor of people who ask
for very heavy equipment when they are
already very old, and therefore at the
detriment of all others, including the
young. 
That's it, so energy is everywhere.
So, once I told you that, we're going
to do a tiny little bit of economics.
This is the planet Earth. 
So, the planet Earth, as Coluche used
to say, is square with its eyes in the
corners.
No. 
The planet Earth is made up of
resources in an anthropocentric vision. 
So I'm going to put it from the point
of view of Men. 
And, from a human perspective, planet
Earth is a resource. 
All right?
This is where we live, this is our
home, this is where we live, so these
are resources to which we have access. 
These resources, I will classify them
into two categories, which are on the
one hand resources that are renewed on
short time scales. 
I call them renewable.
And, on the other hand, resources that
do not renew themselves on short time
scales, that I call non-renewable. 
Copper ore is definitely non-renewable.
There is no large-scale transmutation
on Earth that replenishes the copper
ore stock. 
Fossil fuels are renewable if you wait
a few tens of millions of years. 
It's not a short time scale, so I put
them in non-renewable. 
On the other hand, grass or solar
radiation is reasonably renewable on
short time scales.
These resources are all free and they
are the result of everything that has
happened since the Big Bang, all free
of charge.
So, since the Big Bang, proton soup and
everything else, a whole bunch of
processes have taken place. 
And today, we have Mendeleev's table
and all the combinations that it offers
to us on the surface of the planet.
For free. 
All this was done for free.
We get there, and we decide to have a
productive activity.
So, what is productive activity for
Men?
It is using this great horn of
abundance of resources and transforming
resources into something else that is
more interesting than the original
resource. 
For example, I have coarse flints: it
is more interesting to have carved
flints to chase after my prey.
For example, I have deers: it's more
interesting to have carved deer antlers
to make a number of things out of them,
etc.
So, the productive activity of Men is
just that: I use existing resources, I
transform them, transformation =>
energy: I use energy.
At the time, obviously just the one of
my arms, my legs and fire.
And I do something else with it. 
And then, over time, we will increase
the energy we will seek to have at our
disposal.
So I repeat: 500,000 years of energy
transition, which will make it possible
to increase everyone's production
capacity.
So we extract resources faster and
process them faster.
As soon as non-renewable resources are
extracted from the environment and
transformed into something else, the
stock of non-renewable resources
declines. 
So at first, it does not decline
quickly, although it would seem, for
example, that on flints there may have
been local shortages in the Paleolithic
period.
So we have been able to have, from time
to time, local resource shortages.
So, don't laugh because at the time
they were dying.
And then, over time, we also understood
that there was a part of what we were
transforming that we could keep to
accelerate future transformation.
It's called capital. 
So, capital is the part of production
that is not consumed immediately and is
reusable to increase future production.
So, this is all really good. 
We grow and multiply.
We are producing more and more, so we
are emptying non-renewable stocks more
and more quickly. 
And then, at some point, you become so
productive and so numerous that you
also start emptying renewable stocks.
Today, we have begun to empty stocks of
species that were renewable, for
example. 
We have started to empty the stocks of
forests that were renewable. 
We started to empty fish stocks that
were renewable, and so on. 
We are even beginning to empty the
stocks of slowly renewing soils. 
So we started to empty a number of
stocks that were renewable. 
And then I said transformation, so I
said energy. 
But I said transformation, so I also
said undesirable by-products of
transformation.
When you transform, there is always a
time when you have an unwanted
by-product of the transformation. 
These undesirable by-products of
processing have been given a name in
French, it is called pollution.
So pollution is all the undesirable
by-products of processing, i.e. those
that will have an effect that we are
not looking for.
And, not only are we not looking for,
but they’re bothering us instead.
So, basically, pollution is all about
trouble.
So, in more orthodox terms, it is all
the products that will be introduced
into the environment and will have the
effect of degrading the quality of the
remaining assets. 
That's what pollution is.
In there, with this definition, you can
bring in climate change, biodiversity
erosion, overfishing, and so on. 
And so, in this case, the economy that
we have set up, which I will detail in
a little while, consists in counting
that annual flow and considering that
that is all that matters.
I will explain why. 
So, basically, we count the moment when
we transform, since transformation is
Man's action and money only pays men.
So, in that case, we decided that the
only marker of this physical flow, of
the system I am presenting to you here,
is the monetary counterpart of the
annual transformation flow. 
And this annual transformation flow, in
the jargon of economists, is called
GDP, it is the monetary counterpart.
We might as well have had an accounting
that would say: “I count «plus» what I
do, «minus» what I destroy. 
And then, on the day the marginal value
of the last car I built is less than
the marginal value of the last bits of
iron ore, copper ore, lithium ore,
vanadium, chromium and fossil fuels I
used to make this car, I stop making
cars and live “happily ever after”
with existing cars. ”
You can see that's not what we're
doing. 
In fact, the economic system is a
system without absolute limits. 
Nothing in the economic system tells
you: “When GDP reaches 80 trillion
dollars on Earth, it stops.
We made a system that is potentially
infinite, which is why it is so
attractive. 
Then why did we do it?
Because, two centuries ago, when we
start theorizing about economics, you
have a number of people who make the
following observation, they say:
“Economics is the management of what is rare.”
What is rare two centuries ago? 
It is the human factor.
You have lots of species, lots of space,
lots of World.
The United States are just at the
beginning of their colonization, Russia
is huge, and so on. 
We don't know how far the ocean goes.
No resource issues. 
What is rare two centuries ago is the
human factor. 
And so, two centuries ago, economists
like Mr Say, who wrote exactly what is
written here, said to themselves: “At
first order, I will just look at the
limitation coming from Men, the rest I
do not care, I do not count.”
And if I consider that the resources
are infinite, you agree with me that
any variation in stock is zero.
Delta-stock on infinity, it's always
zero.
So I'm going to count for zero the
factors that don't come from Men.
Approximation to the first order which
is still the one of the economy today.
So I'm going to say something that will
hurt your Director of Studies who just
came in. 
The whole economy you are taught at
school is wrong when it comes to
approaching the human system as a
whole. 
When it comes to approaching trade-offs
within the human system, it works. 
When it comes to approaching the whole
of Men in their environment, it only
says nonsense.
That's not what it's for. 
So, in other words, the economics that
I learned in school and that we are
still learning today is that the
productive system is fuelled by two
factors of production, human capital
and human labor, and that is enough to
fill the supermarket.
It doesn't take into account machines,
it doesn't take into account resources.
So it turns out that at the time, we
could have won the battle in another
way. 
It so happens that two centuries ago,
Mr Charles Dupin, a polytechnician,
therefore someone very decent, baron
of his state, made a first conversion
calculation in “slave-equivalents”.
So, at the time, he didn't call them
“slave-equivalents”, he called them
“worker-equivalents”.
And, Mr Dupin say: “I will look in
France and Great Britain at the
productive resources available to us in
addition to Men [so he had understood
everything about physics] and I will
convert them in the equivalent of
human workers.
So I take the population, I make them
human workers […]” and by the way, he
counted children for a quarter and
women for half – and we wonder if
that's not where “my half ” comes
from when one talks about one’s
partner. 
No, no, I assure you.
Where else would it come from “my half”?
So it could be half a couple, that's
another explanation.
But we wonder if that's not where it's
coming from.
So he is taking the population and he
is also taking the auxiliaries that
are, at the time, boats, mills, etc. 
And then, Mr Dupin, he says: “If I
take the population AND the
auxiliaries, then it becomes normal
that Great Britain, which has a
population about the same size as
France, already has three times more
industrial production.
This is normal because it is not only
Men who work.
There are also mills, draught animals
and boats.
If, at the time, we had listened to Mr
Dupin and not Mr Say, it is not
completely certain that we would have
built the economy in the same way.
It's not completely certain. 
And what the physicist says is:  “What
I have on the right is my 92 elements
of Mendeleev's table arranged in a
different way than what I had in the
original resources.
It's just that.”
Do you agree with me?
There is nothing but the 92 elements of
Mendeleev's table in all objects of
everyday life. 
Nothing else.
Do we agree? 
Except we didn't find them in this form
in the environment. 
So I found them in a form, and I
transformed them. 
So, for that I have to find my 92
elements of Mendeleev's table, it's
called resources and transform them.
My transformation capacity (it is the
order of magnitude calculations I
showed you earlier) comes for 1 from the
muscles of Men and for 200 from Ironman.
That is to say, from the park of
machines we have built.
This is my ratio of 1 to 200 that I
developed for you earlier.
The capital in this story is made like
everything else.
That is to say, this building, which is
a capital element, was made like the
rest by transforming natural resources. 
So, this building is, like the rest,
made by transforming iron ore, i.e.
iron and oxygen arranged in a certain
way, i.e. stones (so natural
resources), i.e. paint (transformed
natural resources), etc. 
So it's done exactly the same way, just
it doesn't get destroyed when you use
it.
That is to say, while we are in this
room, for your greatest pleasure and
for mine, it does not collapse. 
And there you understand that it is not
only Men who are a limiting factor of
the system.
In the modern world, energy is a
limiting factor of the system.
In other words, if I deprive my fleet of machines of energy, I will
deprive my productive system of its
production capacity even if the bankers
are very friendly and even if the
unemployed are ready to go to work.
That is not enough in the world we live
in.
And if I deprive the system of
resources, for example I have no fish
to catch, the GDP of fishing is zero.
The GDP of Léon de Bruxelles is zero.
Well they have to switch from mussels and
chips to steak and chips, but otherwise
it is zero, and so on. 
So if you don't have the resources and
energy, you won't have the production
even if you have highly motivated
workers and even if you have very
friendly bankers.
So historically, until now, all this
has not been a limiting factor.
The limiting factor is indeed Men. 
You have here the reconstruction of GDP
since the year zero. 
That is, since the birth of Mr Jesus
Christ. 
So you see that, as long as there are
no significant quantities of mechanical
auxiliaries, there is no growth.
The population is reasonably stable at
that time as well.
At that time too, as a man is
productive as his muscular system and
no more, the most populated country in
the world has the first GDP on the
planet. Which is?
China. 
Absolutely.
So, China, today, is saying one thing in
the concert of nations: “Listen, don't
make us laugh. 
For two millennia, we have been the
dominant economic power on the planet. 
So just because a century of oil has
put the United States in our place does
not mean that it will change our view
of the world. 
So first we'll find our place and then
we'll talk. 
That's about the way things are.
Very few mechanical auxiliaries, very
little growth.
With the mass arrival of mechanical
auxiliaries and fossil fuels, and bang,
economic models say that we will have
three percent growth for all eternity.
Then don't laugh. 
I happen to be part of an organism
called the High Council for Climate. 
Three weeks ago, we were presented with
the National Low Carbon Strategy drawn
up by some of your predecessors, whom
were obliged to say that a sharp
reduction, a 6 to 7-fold reduction in
the amount of fossil energy we would
bring in France, would increase the
French GDP. 
It's in there, it's in there.
Because business models tell you that. 
Because economic models can tell you
that we increase GDP by dividing energy
by 10 since energy is not an input.
There is no problem, no problem. 
So in the meantime, that's not what's
happening. 
I present to you the best macroeconomic
model in the world, called a straight
line.
Here you have in abscissa the quantity
of energy used by Men, i.e. I repeat,
the number of machines in service. 
And so, in ordinates, the economic
value of the production. Which follows in
a more or less linear fashion.
Very simple. 
Really very simple.
This is valid in absolute value, it is
also valid in variation.
Here you have in green the annual
variation in the amount of energy used
on Earth, i.e. the annual variation in
the number of machines in service, and
in blue, the annual variation in human
economic production.
You see that: give me one, I give you
the other; and give me the other, I
give you the one. 
All right, I'll tell you again in a
different way. 
Euros only measure a flow in monetary
terms, which kilowatt-hours physically
measure.
So, it's two units of account that look
at the same thing, that is, a
transformation flow. 
I come back to my curve that I showed
you earlier about energy supply per
person and I will make another comment
this time. 
You can see that over the period up to
the oil crisis, the energy supply
increases by 2.5% per year per person.
This means that the number of machines
per person is increasing by at least
2.5% per year. 
You have a little bit of energy
efficiency added. 
This means that as long as you do not
have limiting factors on the resources
to be processed, the physical
production per person increases by at
least 2.5% per year.
And so, the monetary counterpart of
this production increases by at least
2.5% per year. 
Actually, you'll see, it's a little
more. 
After the oil shocks, you can see that
the pace is slowing down. 
So in fact, it is totally slowing down
for the OECD countries, which are
called the rich countries, the western
countries; and the surplus you have
there is the rise of China, and then
later of the other emerging countries. 
And that translates into a rise in the
quantity of coal per person, which is
an average effect.
In fact, in Western countries, the
amount of coal used is not increasing,
even decreasing slightly. 
However, it is exploding in China.
And today, China uses half of the coal
consumed in the world.
At this point, the system starts to
slow down a little.
That is, we continue to have an
increase in physical production
per person, but much lower, and much lower than
the rate of redistribution to which we had
become accustomed during that period. 
That is to say, in all the Western
countries of the world, a welfare state
has been organized, more or less.
More or less. 
Less welfare in the United States, more
welfare among the Scandinavians. 
But in all countries of the world, a
welfare state is organized that
redistributes part of what is produced
and the growth rate of redistribution
is in line with the growth rate of
production, i.e. a few percent per
year.
And we do not put in the system the
capacity to correct it quickly if
growth slows down. 
In other words, we don't tell public
agents: “Well, we warn you, if growth
runs out of steam, increased wages with
seniority, it stops.”
We don't tell retirees: “We warn you,
if the rate of growth slows down, you
will automatically retire later and be
paid less.” Etc. 
We're not saying that whole thing.
We say: “No, no, if growth slows down, we
continue to pay you the same and we
increase your wages with seniority in
the same way.”
At that moment, you have to find the
money somewhere and you get into debt.
In all Western countries, public debt
was non-existent before the oil shocks.
It appears and develops… well very weak
before the oil shocks.
It appears and develops everywhere. 
So, it is not only the French
politicians which are incompetent. 
It appears and develops everywhere in
all Western countries after the oil
shocks precisely for this reason.
Because the rate of increase in
production per person is no longer
sufficient to ensure the rate of
increase in redistribution per person.
And starting from 2005 -- and I will tell you why in
the next few months -- the per capita
energy supply is beginning to become
more or less constant again in the
world. 
In fact, it is declining in the OECD
area, I will show you right after. 
And then the system goes to hell:
massive financial crisis of Lehman
Brothers which is a consequence of what
I'm telling you (I'll show you in a
little while chronologically) and not a
cause. 
Debt begins to explode.
We come to something that has been
unknown for a very long time called
negative interest rates, etc. 
And that is the system's response to
the fact that we built something that
depended on energy abundance, and that
this energy abundance is slowly
starting -- slowly starting -- to fray.
And by the time you're my age, we're
going to accelerate in that direction.
So that's why your future won't be a
continuation of the past.
So, a few curves to finish. 
You have here the variation in GDP per
person in the world, and therefore the variation
of economic output per person in the world
since 1960. 
You see it here in terms of annual
variation. 
And then I put in orange the averages
over three periods: until the oil
crisis, between the oil crisis 79 and
the oil crisis of 2007-2008, and since
the shock of 2007-2008.
There is a small artifact that I'm not
going to talk about today because it's
too long, but debt is something that
makes it possible to make GDP without
production. 
It's a little complicated, but here
you're starting to have a side effect. 
What you see is that: in the era of the
Glorious Thirty, energy grew strongly
per person, and production per person
grew even more strongly, because there
was a gain in energy efficiency in
between. 
Engineers know how to make a more
efficient car, which advances with less
oil if it is the same car, or a larger
car sold more expensive with the same
amount of oil.
After that, you see that the energy per
person is increasing less quickly
(it is actually 1% rather than 0.5%) and
you see that the GDP per person is
starting to grow less quickly. 
And since the episode... Well it's very
contrasted there, you also see that
there's a big episode of volatility.
You can see it's dropping. 
In fact, you have two regions in the
world that are evolving in a very
discriminated way from that moment on:
the OECD and the rest; and I will show to you 
where we live, that is, the OECD.
So the OECD: this is how a first piece
of the OECD evolves, i.e. the European
Union in which we live. 
Until the oil shocks, the energy supply
per person increases sharply. Between
the oil shocks and 2006 -- and you see that
the maximum is in 2006, two years before
Lehman Brothers.
So it was not Lehman Brothers that
caused the economic crisis that caused
a fall of the amount of energy used. 
It was the contraction of the
energy supply that slowed GDP and made
it impossible for borrowers to repay
the debt they had started to incur when
the economy first slowed down here.
It's a two-triggers-gun. 
There, we start to get into debt to
compensate for the fact that the energy
stops increasing, and there, at the
moment when the energy starts to
decrease, we no longer even have the
capacity to get back into debt at the
right speed to repay the Ponzi scheme
we had started creating. 
There you see an effect of the thing I
will tell you about next time, which is
the replenishment of the world energy
market with source rock oil and gas in
the United States, and oil in
particular. 
What you see in Europe at that time is:
the GDP per person is rising sharply at
the time of the Glorious Thirty; energy
per person is stopping growing but GDP
per person is still rising; and you see
that ever since 2006, the increase has been
almost zero.
And, by the way, Europe's industrial
production today is still lower than it
was in 2007. 
Ton-kilometers by truck today in Europe
are lower than they were in 2007. 
The construction index today in Europe
is lower than it was in 2007. 
So part of the increase in GDP that we
have had since 2007 is false GDP. 
It is an accounting artifact that is
basically a bad correction of
inflation, if I say it differently.
So, at that moment you ask British
people: “Are you happy?”
British say “No”. 
I would remind you that a referendum,
in general, you answer the person who
asks the question, you do not answer
the question. 
De Gaulle learned it at his own
expense and besides, you remember the
result of the first referendum in
France on the European Union...
So, of course, we rephrased the question in a
different way. 
But so, historically, a referendum is
still a very good way to answer to the
person who asks the question and not
the question itself. 
So the English say to the person asking
the question: “We are not happy with
the way things are going.”
By the way, as soon as the GDP per
person no longer increases and you
create a space of free movement in an
area where you have a difference of 1
to 5 between what people in the East
earn and what people in the West earn,
what do you think is happening? 
It balances out.
So when you're in an expanding universe,
it doesn't matter. Because you can
increase people's incomes on one side
while you continue to increase or at
least you don't decrease people's
incomes on the other side.
So, when Spain and Portugal join the
European Union at a time of strong
growth, the purchasing power of the
French can continue to increase at the
same time as the purchasing power of
the Spanish increases significantly.
But when you bring in 2005 (that is to
say two years or a year before the
maximum European energy level) the
Eastern European countries by telling
them: “Come and dance, your GDP will
increase at the same time as ours will
continue to increase.”
And then, crack, the energy per person
starts to drop. 
At that moment the GDP of the area no
longer increases, your effect of
connected vessels applies, and all that
the Eastern countries will take, it is
the Western countries that will lose it.
It's mechanical.
Then, there are two ways to lose it. 
The Polish plumber comes to London and
it gives you that result. 
And the second way to lose it is
Renault investing in Romania, and at
that moment, you have the French
workers yelling. 
And these are the two ways in which the
rebalancing process applies. 
This is just the beginning.
As long as we stay, I'm not playing
politics with two pennies in my hand,
but I'm just saying that as long
as we stay in a space where everyone
moves and pays as they please, when you
have differences in initial potential
that you can't homogenize from the top,
you're going to have rebalances with
loss for a number of people. 
So the temptation for Frexit, Italexit,
Espaxit and Swedexit will increase. 
All these pressures will increase
because of this. 
And, originally, you find energy.
When you do a trend analysis, you note,
by the way, that this variation in
energy supply per person is in fact
the result of a very strong trend (and
I will come back to it in the next
course) that has been expressing itself
for decades. 
Here you have a curve that gives you
the variation of the European Union's
energy supply.
So it's not its supply, it's its
variation over the past 50 years.
What you see is that the variation with
large gaps follows a trend where it is
strong, a little less strong, a little
less strong, a little less strong, and
at some point, we enter into negative
territory and, by the way, at that
moment, we start to have something that
is reasonably volatile.
If we say that this second derivative
has good reasons to be representative
of the internal dynamics of the
process, then you tell yourself:
“Well, the rest of the story is that
energy supply will continue to decline
and therefore the GDP growth rate,
which was increasingly low over the
same period, will continue to decline
and move into permanently negative
territory.”
So the life that awaits you and me for
the next few decades, if everything
goes well, is likely to be nothing like
what I have known since I was born. 
That is to say, it will not be a world
of expansion, it will be a world of
contraction.
So we're going to need your creative
genius because I assure you that
managing a shrinking world is much more
challenging as a constrained
optimization exercise than managing an
expanding world.
So, we're really going to need you. 
We also need me, but we're really going
to need you... In the sense that we're
really going to need the best selected
brains in the country to tackle one of
the toughest problems we will
have to solve, which is to keep the
system more or less stable in a context
of shrinking available resources. 
I can assure you that what you saw in
the written and oral part of the
contest was an easy part compared to
that. 
I take the OECD area as a whole and I'm
going to end up with that. 
Same motive, same punishment.
The supply per person increases until
79, peaks in 2006 -- and this is also
true in the United States. 
In the United States, the energy supply
per person went through a maximum two
years before Lehman Brothers, I insist.
And, you also have this evolution that
actually reflects a trend evolution
that has taken place for a very long
time, and therefore it will probably
happen about the same thing in that
area and then in the world as a whole.
There you go. 
So, what I told you during this first
module is that the world in which we
live has been enabled notably by -- not only by --
but notably by the fact that we
have found free “pockets of sunlight”
under our feet, as Yann Arthus Bertrand
puts it very nicely, that is to say fossil
energy. Free, with a very high
calorific value -- so a very high
exothermic capacity -- that allowed us to
transform at an accelerated rate all
the other resources (also free) that we found
on Earth, and it has enabled us to
build the socio-economic system in
which you grew up,
that is, most of the people in the city,
most of the people in service activities,
everyone eating steak at every meal,
people with a lot of free time and the
demands of the MEDEF and the CGT that can be met without any problem.
That's the world we grew up in.
And, by the way, MinesParisTech's
international exchange program since
you need planes for that. 
And, the way I count the transformation
flow is a way that is unlimited by
construction, since the only thing that
was really annoying in the deal, that
is the fact that the Earth is 13,000
kilometers in diameter and not 14,000
and not 1,5000, I ignored it, I put it
under the rug. 
And, on the basis of this axiom, which
is only an approximation to the first
order, I have refined my visions for
two centuries but without questioning a
fundamental axiom which is: Nature is
free. 
So, obviously, I don't see that limit
because it's not in the system. 
In the next course, we will not look at
that, which is one of the first limiting
factors of the system, i.e. pollution,
and we will focus on a very specific
pollution called climate change.
So climate change is only the
downstream consequence of this
transformation flow. 
At the next course, what we will really
look at, is the bottleneck that can
eventually apply upstream of the
system, and which is called the supply
of fossil fuels.
Obviously, if we had the time, we could look at
the supply of metals, this is another
possible limiting factor for the
system.
Species supply is another possible
limiting factor of the system, etc.
But then, we will look at and discuss
the upstream supply of fossil fuels,
i.e. of transformation capacity. 
So that's the picture we're going to be
in for the next course I'm going to
give you.
Have a good evening.
