This New Scientist video is a superb illustration of the tough emissions targets the world needs to be thinking about. More details in the NS story here. The basic premise is that if we take a 2ÂºC target seriously, then we have to limit our total emissions to 2050 to about 750 billion tonnes of carbon. Then divide that up by the current population of the world, and allocate countries a carbon budget, based on their population, that they can burn by 2050. Not good news for big emitters like the US, which would burn its total budget in about 12 years at current rates. As the presenter suggests, this is only a thought experiment not a model for policy, but it provides a realistic context for policy making. Required viewing.