The majority of world leaders agree that we must keep global warming from exceeding 2 degrees Celsius above pre-industrial levels if we're to avoid catastrophic climate change. They agree to that even as they embrace policies far more likely to result in 4C or more of warming by mid-century. Write it off to cognitive dissonance.
Now a team of eminent climate scientists warn that we've underestimated the problem and even holding the line at 2C won't be enough to avoid global disaster.
The limit of 2C of global warming agreed by the world's governments is a "dangerous target", "foolhardy" and will not avoid the most disastrous consequences of climate change, new research from a panel of eminent climate scientists warned on Tuesday.
In a new paper, the climate scientist Professor James Hansen and a team of international experts found the most dangerous effects of a warming climate – sea level rise, Arctic ice melt, extreme weather – would begin kicking in with a global temperature rise of 1C.
Allowing warming to reach 2C would be simply too late, Hansen said. "The case we make is that 2C itself is a very dangerous target to be aiming for," he told the Guardian. "Society should reassess what are dangers levels, given the impacts that we have already seen."
The Intergovernmental Panel on Climate Change warned in its major in October that the world had only about 30 years left before it exhausted the rest of the 1,000 gigaton carbon emission budget estimated to lead to 2C warming. But Hansen and his colleagues warned that the UN target would not avoid dangerous consequences, even if it kept within that carbon budget.
"Fossil fuel emissions of 1,000 gigaton, sometimes associated with a 2C global warming target, would be expected to cause large climate change with disastrous consequences. The eventual warming from one gigaton fossil fuel emissions likely would reach well over 2C, for several reasons. With such emissions and temperature tendency, other trace greenhouse gases including methane and nitrous oxide would be expected to increase, adding to the effect of CO2," the researchers said.
"The main point is that the 2C target – which is almost out of reach now, or quickly becoming out of reach – is itself a dangerous target because it leads to a world that is greatly destabilised by rising sea levels and massive changes of climate patterns in different parts of the world," said Professor Jeff Sachs, director of the Earth Institute at Columbia University, one of the PLoS paper's authors.
Oh well, you can't say we weren't warned - all of us, time and time again. This is one horror story, the greatest in the history of mankind, that we have walked into with our eyes wide open having chosen not to act while we still had time. To those of you born after 1970, all I can say to you is "good luck." You'll be living in very interesting times. To those of you born before 1960, count your blessings.