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| Earth on Apr 21, 2009

James Hansen: ‘We’re in a CO2 danger zone’

Carbon dioxide levels today are unacceptably high, says NASA scientist James Hansen. Hansen talked to EarthSky about the dangers of atmospheric CO2 – and what can be done to bring the levels down in the future.

James Hansen: I do think the public, in general, trusts scientists. If we’re careful in explaining things and do a good job at that I think it will help in getting the actions that are needed.

James Hansen is the director of the NASA Goddard Institute for Space Studies in New York. In 2008, he was selected as the EarthSky 2008 Science Communicator of the Year – the scientist who best communicated with the public on vital science issues or concepts in 2008 – by a panel of over 600 EarthSky Global Science Advisors. Hanson is also lead author of a new study that claims Earth’s level of atmospheric CO2 is dangerously high. In the two EarthSky podcasts above, Dr. Hansen speaks with EarthSky’s Jorge Salazar about the Earth’s climate reaching a ‘danger zone.’

James Hansen: We didn’t realize that we already have increased CO2 into a dangerous zone. What’s become clear from a number of different criteria is that the safe level of CO2 is no more than 350 parts per million, and probably less, which requires significant changes in our energy use. We simply are not going to be able to burn all the fossil fuels.

CO2 levels today sit well over what Hansen believes is an acceptable level. They continue to rise mainly from our use of fossil fuels like coal and oil, and Hansen believes we could cause major changes.

James Hansen: We can already see that the ice sheets are beginning to disintegrate.

Hansen and colleagues analyzed ice core data going back 65 million years to see how sea level responded to CO2 in the air.

James Hansen: The last time all the fossil fuels were in the atmosphere instead of in the ground, there was no ice on the planet. Sea level was 250 feet higher.

Hansen added that it’s not too late for the world to act. He believes one step would be to phase out the use of coal by 2030.

James Hansen: Coal is the primary source of atmospheric carbon dioxide, and it’s very dirty stuff. It’s got mercury in it. It’s got heavy metals. And these things are polluting the world atmosphere and ocean. That’s why you’re told, ‘don’t eat fish too much,’ because there’s too much mercury in it. All of that mercury is coming from coal, from coal-fired power plants. So we’ve got to figure out other sources of energy. And that is possible.

Hansen talked about the bright side of moving beyond fossil fuel.

James Hansen: The world beyond fossil fuels is going to be a much cleaner world. You know, there are several hundred thousand people per year who die of air pollution, mostly in places like China and India where the air pollution is much worse. But even in the United States, 30 or 40 thousand people per year die of air pollution. And most of that comes from fossil fuels. So when we develop clean energy sources, and we have vehicles that do not emit air pollution, it will be a better world.

Hansen warned that the problem is urgent.

James Hansen: If we go even another ten years building more and more coal-fired power plants, we will have the CO2 up to a level that there’s no practical way to get it back down. But if we would get the message and get on to a new path, then we can solve the problem and, as I’ve said, it is a brighter future if we do that.

Hansen believes that scientists are beginning to speak out more.

James Hansen: Twenty years ago when I testified to Congress, I got a lot of flack from other scientists. But now, that’s changed. There are a lot of scientists who agree that we do have to speak out.