The arxiv isn’t usually the place where climate scientists make predictions about global warming but yesterday, they made an exception. A group led by James Hansen, one of the world’s leading climate scientists who works at NASA’s Goddard Institute for Space Sciences, warned that global warming is having much worse effects on Earth’s climate than thought. They say without immediate action, humanity is in danger of “seeding irreversible catastrophic effects.”
The background, in case you’ve been stuck on a desert island for the last few years, is that CO2 levels in the atmosphere have doubled from 180 ppm in pre-glacial times to 385 ppm today, most which has come since the industrial age began. “Humanity today, collectively, must face the uncomfortable fact that industrial civilization itself has become the principal driver of global climate,” says Hansen and co.
So what to do? The International Panel on Climate Change suggests that global warming of more than 2-3 degrees C may be dangerous, the EU says we should attempt to limit global warming to no more than 2 degrees C while Hansen himself has said that 1 degree C should be the maximum we should tolerate. This last estimate implies a maximum level of CO2 of 450ppm.
Now Hansen says he was wrong and that we need to aim for a CO2 level of only 350 ppm to be sure of maintaining the climate in the state we’re used to. Because if we carry on as we are, the world is going to change in ways that hard to imagine. I’ll let Hansen do the rest of the talking:
“Present policies, with continued construction of coal-fired power plants without CO2 capture, suggest that decision-makers do not appreciate the gravity of the situation. We must begin to move now toward the era beyond fossil fuels. Continued growth of greenhouse gas emissions, for just another decade, practically eliminates the possibility of near-term return of atmospheric composition beneath the tipping level for catastrophic effects.”
Ref: arxiv.org/abs/0804.1126: Target Atmospheric CO2: Where Should Humanity Aim?
Ref: arxiv.org/abs/0804.1135: Supporting Material