>>Today we will talk about climate change.
Is our climate changing? Now you have to be
careful here. You have to think about climate
change on a longer timescale than changes
in weather in a day, or a week, or a month,
or even a year. You have to think of it in
terms of hundreds of years. For example, for
the last hundred years or so, global temperature
has been rising, but very slowly. It's rising,
but slowly. In 1998, there was a paper published
where a graph was shown that showed that the
temperature change over the past 2,000 years
showed a gradual cooling but then a dramatic
increase in the last hundred years. And this
graph is commonly referred to as the hockey
stick graph. And basically you think of the
handle of the hockey stick would be the gradual
decline of temperatures, and then the rise
in temperature in the last hundred years would
be that part of the hockey stick that you
hit the puck with. Now the issue is not so
much about whether this has occurred or not,
because it appears, we think we have good
evidence that temperature has increased. But
the issue has become: what is causing the
increase? Is it natural or is it related to
human activity? This is the debate now.
The argument for human activity is the following:
burning of fossil fuels and so on causes release
of CO2, which is a greenhouse gas. That greenhouse
gas goes up into the atmosphere. It causes
heat to be re-radiated back to the Earth,
and that can cause global warming. Most but
not all scientists believe this is taking
place today. For example, 96 percent of all
climate scientists think that we are influencing
our climate.
So what are the implications of this temperature
increase? There are many that we need to consider.
Here are a few. As temperature goes up, ice
melts, and sea level goes up. 80 percent of
the people on the Earth live near the coasts,
and that has profound implications for cities
like New York and New Orleans, which are right
near the coast. There will also be changes
in crop patterns. And according to many climate
scientists, extreme weather will become more
likely.
