An excellent look, by Justin Gillis at the New York Times, at how the world decided that it should try to limit global warming to 2 degrees centigrade, and how that target might not actually be the right target:
Yet even as the 2C target has become a touchstone for the climate talks, scientific theory and real-world observations have begun to raise serious questions about whether the target is stringent enough.
For starters, the world has already warmed by almost one degree Celsius since the Industrial Revolution. That may sound modest, but as a global average, it is actually a substantial number. For any amount of global warming, the ocean, which covers 70 percent of the earth’s surface and absorbs considerable heat, will pull down the average. But the warming over land tends to be much greater, and the warming in some polar regions greater still.
The warming that has already occurred is provoking enormous damage all over the planet, from dying forests to collapsing sea ice to savage heat wavesto torrential rains. And scientists are realizing they may have underestimated the vulnerability of the great ice sheets in Greenland and Antarctica.
Those ice sheets now appear to be in the early stages of breaking up. For instance, Greenland’s glaciers have lately been spitting icebergs into the sea at an accelerated pace, and scientific papers published this year warned that the melting in parts of Antarctica may already be unstoppable.
The 2 degree target always had a significant degree of uncertainty attached to it (though it was useful to focus attention on some target). To consider it a threshold below which we would somehow remain “safe” was the wrong way to look at it. Yes, 2 degrees might be a threshold beyond which certain irreversible catastrophes would follow (melting ice sheets). But there is plenty of catastrophe below the 2 degrees threshold, as well, as we are already seeing (most notably, the acidification of the oceans). It has always been the case that a lot less warming would be a lot better for the planet.
This is a challenge to global climate policy, and as Gillis notes:
So, even as the world’s climate policy diplomats work on a plan that incorporates the 2C goal, they have enlisted scientists in a major review of whether it is strict enough. Results are due this summer, and if the reviewers recommend a lower target, that could add a contentious dimension to the climate negotiations in Paris next year.
Barring a technological miracle, or a mobilization of society on a scale unprecedented in peacetime, it is not at all clear how a lower target could be met.
Actually, it is not at all clear how the 2 degrees target will be met, either. The point is that “a technological miracle, or a mobilization of society on a scale unprecedented in peacetime” is what is needed regardless of the target. And the sooner political leaders (and the media, and then the public) come to that realization, the better off we will all be.
Climate change is an unprecedented challenge, so there is an obvious case to be made for an unprecedented mobilization of societies and technologists. We may be in “peacetime”–and therefore relatively complacent– according to conventional definitions of peace and war. But we are facing an existential threat that is arguably greater than any threat of war experienced in human history (and orders of magnitude greater than the threat posed by Islamic extremism and ISIL, to which we devote inordinate and inexplicable amounts of attention and resources). That should count for something.