New paper argues 2 degree climate goal likely to hit tipping point

The combined effects of overshoot and climate cascades have often been overlooked - until now.

Diagram of interrelated climate change tipping points. Wunderling, N., Winkelmann, R., Rockström, J. et al. Global warming overshoots increase risks of climate tipping cascades in a network model. Nat. Clim. Chang. (2022).

One of the less-appreciated insanities of our current plan for managing climate change is that the IPCC’s 2-degree warming goal isn’t about limiting climate change to 2 degrees. That’s just where we hope to end up. But before we get there, policymakers take for granted that we will probably blow past that goal before drifting back to our target — a phenomenon they call “overshoot”. The Climate Action Tracker, for example, reports that

the high estimate of our current policy projection would lead to a warming of 2.9°C and rising, while the low estimate results in a median warming in 2100 of 2.6°C and rising.

This is what happens if we actually hit our targets. But if you look at what we’re actually doing, the CAT reports, our “real world action based on current policies” will max out even higher at around 3.4 degrees warming. And while a brief 1.4 degree excursion above-target may seem like no big deal on its face, that could be all it takes to trigger all kinds of irreversible climate processes that rocket us into much higher temperatures, pushing us past the so-called tipping points.

That’s the danger explored in a new paper for Nature Climate Change: Global warming overshoots increase risks of climate tipping cascades in a network model. It was published by a team of scientists associated with the Potsdam Institute for Climate Impact Research (PIK) and the University of Exeter. You can read the whole thing for yourself here, but since the news is buried in bits and pieces amid paragraphs of dry technical exposition and some truly unreadable charts, I thought I’d put together a clearer summary here…