By Ted Nordhaus – Forty years after it was first proposed, the two-degree target continues to maintain a talismanic hold over global efforts to address climate change, despite the fact that virtually all sober analyses conclude that the target is now unobtainable.
But it is worth considering the consequences of continuing to pursue a goal that is no longer obtainable. Some significant level of future climate impact is probably unavoidable. Sustaining the fiction that the two-degree target remains viable risks leaving the world ill prepared to mitigate or manage the consequences.
In reality, most of the climate risks that we understand reasonably well are linear, meaning that lower emissions bring a lower global temperature increase, which in turn brings lower risk.
There are a range of potential nonlinear tipping points that could also bring catastrophic climate impacts. Many climate scientists and advocates argue that the risks associated with triggering these impacts are so great that it is better to take a strict precautionary approach to dramatically cut emissions. But there are enormous uncertainties about where those tipping points actually are.
The precautionary principle holds equally well at one degree of warming, a threshold that we have already surpassed; one and a half degrees, which we will soon surpass; or, for that matter, three degrees. more>