It is tempting to think of climate change as a gradual, linear process that follows the steady accumulation of greenhouse gasses in the atmosphere. The truth may be scarier. Evidence is mounting that critical components of the Earth system could be approaching tipping points that, when crossed, will bring about massive, nonlinear shifts that will themselves accelerate climate change, with disastrous and potentially irreversible consequences for nature and humanity. Faced with this prospect, national governments must cooperate to identify, prepare for and, where possible, head off or mitigate these abrupt and calamitous shifts. As the Intergovernmental Panel on Climate Change made clear in its recent […]