UK Climatologist: Time To Stop Pandering To The Politically Possible, End Meaningless Timelines

EDIT

GL: What happens if the 2 degrees target is missed?

KA: Increasingly I hear murmurs from some policymakers and scientists that 2°C is too challenging, that we can’t do it – though such concerns are typically expressed away from more public fora. And I can certainly can understand why they are saying this. So what about a 4°C rise? That sounds more viable. The carbon budget is larger and hence the rate of emission reduction is much less challenging.

But what exactly does a 4°C increase in global surface temperature mean? Most of the surface of the earth is water, which heats up more slowly. So it relates to a 5-6 degrees increase in average land temperature. This area of science is very uncertain, but the Hadley Centre [climate change research centre at the Met Office] estimates that, on the hottest days, the temperature would be 6-8 degrees higher in China, 8-10 degrees in Europe and 10-12 degrees in New York. Such unprecedented increases would give rise to host of issues about how the aging infrastructure of our cities could deliver even survival-level services.

And what about the people who have not caused the problem, in the lower latitudes? It is hard to be accurate, but the Hadley Centre estimates that, for farmers in lower latitudes, a 40% reduction in yields of maize and rice characterises their 4°C impacts.

This is a world that we have to avoid at all costs. Many scientists suggest that a 4°C rise is incompatible with an organised global community. It is beyond “adaptation”. Yet this review of 4°C temperature rise does not take into account possible feedbacks and other discontinuities, which on average are anticipated to make the situation worse still.

So a 4 degrees future is something we must avoid. And that takes us back to 2 degrees – albeit with increasingly lower probabilities of achieving even this. What does 2°C imply for the wealthy parts of the world, the OECD countries? It means a 10% reduction in emissions every single year: a 40% reduction in the next few years and a 70% reduction within the decade. Such reductions are necessary if poor parts of the world are to have a small emission space to help their welfare and wellbeing improve. Despite the coherence of this analysis, I am repeatedly advised that such levels of mitigation are impossible. At the same time, living as a civilised global community with a 4 degrees rise would also seem impossible. In other words: the future is impossible!

EDIT

http://www.resilience.org/stories/2013-07-05/stop-tailoring-global-warming-scenarios-to-make-them-politically-palatable-says-leading-climate-scientist