The Obama administration
*Some documents use other baselines, such as the "climatological period" i.e. 1950-80, or even more recent periods of three decades. It is important to note whether a given temperature rise is based on pre-industrial baseline or a more recent one. Since temperatures rose by around 0.5ºC between the pre-industrial period and 1950-80 (and more since then), then discussions of future rises need to be adjusted accordingly. International negotiations have generally used the pre-industrial period as a baseline, even though the precise global temperature figures are a little sketchier.
The idea that 2ºC is a "safe" guardrail has a complex history, but it is fair to say that more recent climate science has shifted our understanding of just how dangerous 2ºC is. The expected impacts that were thought to arrive at 2ºC back when it was first established as something of a de facto line in the sand between safe and dangerous climate change are now expected to arrive much sooner, at somewhere between 1 and 1.5ºC. So if the developing consensus ten or fifteen years ago was that impacts associated with 2ºC were a valid danger limit, then really, if we are going to be honest and keep our judgements about what is dangerous, we ought to think that anything much above 1ºC is dangerous.
Unfortunately, going well beyond 1ºC is already guaranteed due to inertia in the climate system. What the US has now publicly acknowledged is what has been widely known for years - that inertia in the political and economic system has rendered 2ºC impossible within current economic and political assumptions.**
**The extent to which decades of failure from US leadership on this issue has rendered such a target politically impossible ought not to be underestimated. Despite featuring prominently in his campaign and inauguration, since coming into office, Obama has barely mentioned it and now puts out ads in support of coal.
To this, I say, "so much the worse for those assumptions". But the status quo would not be the status quo if it didn't try to protect itself from having to change. Unfortunately, climate change by definition rules out the possibility of no change. Our current trajectory is inherently unsutainable, which doesn't mean that polar bears are threatened by it, it simply means it will be not be sustained. Something must give. I would rather that be our political and economic assumptions than the habitability of the planet for as many generations as we can imagine.
We are on track for 4ºC if all nations stick to their current aspirational targets, and something more like 6ºC on our current trajectory, according to the normally conservative IEA. Professor Kevin Anderson, director of the Tyndall Centre for Climate Change in Britain, says that a rise of four degrees would likely be "incompatible with organized global community, is likely to be beyond 'adaptation', is devastating to the majority of ecosystems and has a high probability of not being stable (i.e. 4°C would be an interim temperature on the way to a much higher equilibrium level)." No one really knows what six degrees would mean, though sober-minder scientists start discussing human extinction as more than a theoretical possibility.
So, who's happy with six degrees? No takers? What about four degrees? Professor Hans Joachim Schellnhuber, Chair of the German Scientific Advisory Council, advisor to the German Chancellor Angela Merkel and Director of the Potsdam Institute for Climate Impact Research (PIK) was quoted back in March 2009, saying that on a four degree world the planet’s "carrying capacity estimates [are] below one billion people." So, who's happy to retain our present political and economic assumptions that make 2ºC seem impossible?
Basically, even with our best efforts, on the most optimistic path possible, we are in serious trouble. Facing these realities means shock, grief, fear, anger, guilt and feelings of helplessness. But until we face our situation honestly, we're living a lie. So let us be honest, grieve and then find reasons to fight even a losing battle.