Earth’s tipping points could be closer than we think. Our current plans won’t work
I f there’s one thing we know about climate breakdown, it’s that it will not be linear, smooth or gradual. Just as one continental plate might push beneath another in sudden fits and starts, causing periodic earthquakes and tsunamis, our atmospheric systems will absorb the stress for a while, then suddenly shift. Yet, everywhere, the programmes designed to avert it are linear, smooth and gradual.
Current plans to avoid catastrophe would work in a simple system like a washbasin, in which you can close the tap until the inflow is less than the outflow. But they are less likely to work in complex systems, such as the atmosphere, oceans and biosphere. Complex systems seek equilibrium. When they are pushed too far out of one equilibrium state, they can flip suddenly into another. A common property of complex systems is that it’s much easier to push them past a tipping point than to push them back. Once a transition has happened, it cannot realistically be reversed.
The old assumption that the Earth’s tipping points are a long way off is beginning to look unsafe. A recent paper warns that the Atlantic meridional overturning circulation – the system that distributes heat around the world and drives the Gulf Stream – may now be “close to a critical transition”. This circulation has flipped between “on” and “off” states several times in prehistory, plunging northern Europe and eastern North America into unbearable cold, heating the tropics, disrupting monsoons.
