From an interview with James Hansen of NASA:
Earth Island Institute: You've been called the father of global warming. What does that means to you and is it actually true?Of course it's not true, in the sense that global warming goes way back into the 1800s. The first really good discussion was in the 1860s by John Kendall, who was a British physicist. He speculated that the climate changes from glacial to interglacial were related to changes in atmospheric carbon dioxide, and that turned out to be right. We've only in the last several years realized and proven that about half of the temperature change in the glacial to interglacial changes is in fact due to changes of greenhouse gases - mainly carbon dioxide.
EII: One of the places most recently where you've been rather blunt is on the proposed Waxman-Markey climate bill. How would you summarize the problems that you see?
You can summarize the problem and prove that the bill is inadequate in a very simple way. You just look at the geophysical constraints on the problem and you look at how much carbon there is in oil, gas, and coal. And you see that the oil and gas is enough to get us into a dangerous zone for atmospheric carbon dioxide but not so far that we couldn't solve the problem. But if you add coal and put that carbon in the atmosphere, then there is no practical way to solve the problem. So you just have to look at the proposed policy and see if it allows coal to continue to be used and emit the CO2 in the atmosphere.
You've got to cut off the coal source. Not only does [Waxman-Markey] assure that we will continue to run these coal plants that we have but it actually gives approval for additional coal plants. That simple test tells us that this bill is not adequate.
The basic point - the fundamental problem - is that because of government policies, fossil fuels are the cheapest form of energy. They are not made to pay for the damages they do to human health and the environment. As long as fossil fuels are the cheapest form of energy, they are going to be used. That's why I say you have to address the fundamental problem and that is put a rising price on carbon emissions.