Climate policy implications of nonlinear decline of Arctic land permafrost and other cryosphere elements

TLDR

Arctic feedbacks accelerate climate change via carbon release from thawing permafrost and increased solar absorption due to reduced albedo, with permafrost feedback becoming more positive in warmer climates and albedo feedback weakening as ice and snow melt. The study incorporates dynamic emulators of complex physical models into the PAGE‑ICE integrated assessment model to explore nonlinear Arctic feedback transitions and their impacts on global climate and economy under Paris Agreement scenarios. Dynamic emulators of complex physical models are embedded in PAGE‑ICE to simulate nonlinear Arctic feedbacks. The nonlinear Arctic feedbacks increase the mean discounted economic effect of climate change by +4.0 % ($24.8 trillion) under 1.5 °C, +5.5 % ($33.8 trillion) under 2 °C, and +4.8 % ($66.9 trillion) under current national pledges, making the 1.5 °C target marginally more economically attractive than the 2 °C target, though both are statistically equivalent.

Abstract

Arctic feedbacks accelerate climate change through carbon releases from thawing permafrost and higher solar absorption from reductions in the surface albedo, following loss of sea ice and land snow. Here, we include dynamic emulators of complex physical models in the integrated assessment model PAGE-ICE to explore nonlinear transitions in the Arctic feedbacks and their subsequent impacts on the global climate and economy under the Paris Agreement scenarios. The permafrost feedback is increasingly positive in warmer climates, while the albedo feedback weakens as the ice and snow melt. Combined, these two factors lead to significant increases in the mean discounted economic effect of climate change: +4.0% ($24.8 trillion) under the 1.5 °C scenario, +5.5% ($33.8 trillion) under the 2 °C scenario, and +4.8% ($66.9 trillion) under mitigation levels consistent with the current national pledges. Considering the nonlinear Arctic feedbacks makes the 1.5 °C target marginally more economically attractive than the 2 °C target, although both are statistically equivalent.