No one has done more to alert the world to the peril of climate change than James Hansen. In 1981, Hansen, who has been director of NASA's Goddard Institute for Space Studies for nearly three decades, published the first major scientific paper to show that global warming is driven by man-made pollution. The Bush administration tried to censor his work, and Hansen is sharply critical of the climate bill currently before Congress. Now, he warns, climate change is happening even faster than scientists predicted – and with far greater devastation.
What does the latest science tell us about global warming?
The geophysical constraints of the problem have become quite clear. We've realized that the dangerous level of CO2 – the amount that could push us past the point of no return – is a lot lower than we thought. We're in danger of shooting up to a much higher temperature, comparable to the warmings that caused mass extinctions in the past. If we do, we will lose all the ice in the Arctic, and the permafrost will melt, releasing even more greenhouse gases. Once that happens, the dynamics of the climate system will take over — and then we're out of luck.
How will that screw up the planet in practical terms?
We're already getting more forest fires in the Southwest, and mountain glaciers all around the world are receding faster than we expected. If we stick with business as usual, most of the glaciers will be gone within 50 years, eliminating freshwater supplies for hundreds of millions of people. The ice sheets in both Greenland and West Antarctica are losing mass at a significant rate, which could cause an irreversible rise in sea levels.
How much of a rise in sea levels is possible this century? The current scientific consensus seems to be one meter.
If the ice sheets begin to disintegrate, you could get much more than that. Look at Earth's history: The last time an ice sheet disintegrated, some 14,000 years ago, sea level went up 20 meters in 400 years. That's about one meter every 20 years.
So you're talking about the seas rising by as much as four meters this century?
That's certainly possible. You could see large rises start within several decades.
What would that mean for human civilization?
In places like Bangladesh, almost the entire nation would be under water. Florida will be mostly gone. It's something we just can't let happen.
How can we stop it?
The only practical solution to climate change is to phase out coal emissions. We now know that we have to aim for a level of 350 parts per million or less. That sudden realization has really changed the ballgame. If you phase out coal emissions over the next 20 years, C02 would peak somewhere between 400 and 425 parts per million. Then you would have a solvable problem. But if you let coal use continue, things just go off the chart, and you can't solve the problem.
But won't the climate bill that Congress is considering – which would cap overall CO2 levels and allow industry to trade pollution rights – bring down coal emissions?
No. The crazy thing about "cap and trade" is that it actually locks in the approval to build new coal-fired plants – they're not going to be phased out. The climate bill as it's currently written guarantees that you will have continued coal emissions. Supporters of the bill say, "Well, if there's technology to capture CO2, we'll do that in the future." But they know very well that's not going to happen, because it would double the cost of electricity.
Look at what happened in Japan, which was one of the most ardent supporters of the Kyoto Protocol. They accepted a six percent reduction in their CO2 emissions, and that was to be achieved through cap and trade. But I made a graph of Japan's emissions – coal, oil and gas – and they have actually continued to increase. That's because under cap and trade, the coal industry got big offsets that allowed it to keep polluting.
So what should Congress do instead of cap and trade?
The alternative to cap and trade is to put a price on carbon. You can put a cap on something and squeeze some use of it down, but as long as fossil fuels are cheaper than the alternatives, fossil fuels are going to get used. The only way to solve the problem is to encourage the changes in the energy infrastructure needed to make alternative energies cheaper than fossil fuels. And the way to make them cheaper, to encourage innovations and to get the economies of scale, is to put a price on carbon emissions by taxing them directly. Instead of subsidizing fossil fuels, we should make them pay for the damage they do to human health and the environment. That alone would increase their cost to the point where alternative energies would be viable.
Critics like Paul Krugman, the Nobel Prize-winning economist, argue that a carbon tax would be just as complicated as cap and trade, and provide just as many loopholes to Big Coal.
That's just plain wrong. It's very simple: You put a price on carbon, just a single number, and you put it on at the source, at the mine or the port of entry. You make it a flat tax, and you don't allow loopholes. That's the only way it will work. That's proven, by the way — it has been tried, in Canada, and it is working.
But how will a carbon tax lower pollution in countries like China and India that refuse to reduce their emissions?
Any countries that don't want to have a carbon price, you put a duty on the products you import from those countries. That's a lot simpler to implement than getting every country to agree on reducing emissions. Because every time you need a new country to agree to cap and trade, you have to give them some concession.
So why is President Obama supporting cap and trade?
He seems to have a tendency to be a compromiser. For some things, that's not a bad thing to be. But in this case, the laws of physics don't compromise. If we're going to keep CO2 in a safe range, we can't compromise with the special interests.
Obama seems to be saying, "The current climate bill is the best we can get, given the political realities."
That wouldn't be true if he took a stronger position.
What's it going to take for that to happen?
We have to push in three ways. One is the courts, where a case can be made that we have a legal obligation to future generations to leave a planet that's not in worse condition than what we received from our parents. Another is civil resistance, like the recent march on a coal plant that took place in Washington, D.C. The third is elections. You have to try to use the democratic process, but so far, it's not very effective. That's why I feel disappointed with Obama – because his success was based in large part on young people supporting him in the Iowa primary.
At what point will global warming itself cause so much chaos that people will put pressure on Washington to act?
It's dangerous to rely on something as variable as the weather to push policy. The biggest climate impacts are things that are irreversible, like rising sea levels and the extermination of species. But those things are the boiling-the-frog-in-water problem – they don't happen rapidly enough to cause the public to suddenly wake up.
So is it too late to avoid the worst of global warming?
I'm still optimistic. The problem can be solved – but we have to take action faster. Maybe your readers should be thinking about how they are going to explain what happened to their children and grandchildren. If we don't act now, one day our kids are going to ask, "Why didn't you do something to stop this?"
Obama is smart enough that he may change his position. I hope so, because we can't afford to wait. What he's doing now is in no way adequate – and we're very unlikely to get another president who will be more likely to take the steps that are needed. The fate of the planet is in his hands.
This story is from the August 20th, 2009 issue of Rolling Stone.