Hot on the heels of its announcement of an (intensity-based) short-term emissions reduction target, China has announced that its greenhouse gas emissions will peak between 2030 and 2040, after which they will decline. Its good that they've committed, and the principle of common but differentiated responsibilities means that China is entitled to peak after more developed nations (who as yet have made no such commitment). But the worry is that its too late. If we want even an even chance of avoiding dangerous levels of anthropogenic climate change (which means a two degree rise in average temperature), we need to limit total global emissions to 1000 Gt. China peaking in 2030 means we will never make that target. If we shift that to an even chance of avoiding three degrees - a figures which commits us to severe water and food shortages in much of the developing world - we still need to peak by 2020 to have an even remotely reasonable downwards path. One of the world's largest emitters committing to peaking so late more or less condemns us to four degrees, which means in turn food and water shortages and significant sea-level rise, plus an increasing chance of "non-linear" effects, tipping points with severe environmental effects or which send the entire process out of control.
And OTOH, given that we haven't announced when our emissions will peak (and the government's ETS actually means they will rise), we don't really have much basis to complain.
