The Climate Crunch

From Nature:

Climate Research published in Nature reveals that once a trillion tonnes of anthropogenic carbon has been released into the atmosphere, a peak global warming exceeding 2°C is likely. Yet only a third of economically recoverable oil, gas and coal reserves can be burned before 2100 if that 2°C warming is to be avoided. Faced with this climate crunch, three news features ask: will cutting back on carbon be tougher than we think? Can we drag CO2 directly from the air? And could we cool the planet with a wisp of mist? The worst-case scenario is a world in 2100 that has twice the level of pre-industrial CO2 in the atmosphere. If we want to avoid that, the time for action is now, says Nature.

Time to act

Without a solid commitment from the world's leaders, innovative ways to combat climate change are likely to come to nothing. It is not too late yet — but we may be very close. The 500 billion tonnes of carbon that humans have added to the atmosphere lie heavily on the world, and the burden swells by at least 9 billion tonnes a year. If present trends continue, humankind will have emitted a trillion tonnes of carbon into the atmosphere well before 2050, and that could be enough to push the planet into the danger zone. And there is no reason to think that the pressure will stop then. The coal seams and tar sands of the world hold enough carbon for humankind to emit another trillion tonnes — and the apocalyptic scenarios extend from there.

More here.