>>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..