Evolution of Heat Extremes Under Net-Zero CO2 Emissions

Abstract

Anthropogenic emissions of greenhouse gases have warmed the planet by around 1.3°C and have contributed to the intensification of heat extremes. To stop continued global warming, we understand that we must reach and sustain net-zero global CO₂ emissions, however, there is limited knowledge on how heat extremes might change in net-zero futures. In this study, we explore possible changes in temperature extreme intensity over the century after net-zero CO₂ emissions using projections from Earth System Models in the Zero Emissions Commitment Model Intercomparison Project (ZECMIP). Specifically, we investigate how regional single-day temperature extreme intensities scale with global mean surface temperatures changes before and after net-zero CO₂ emissions. We also explore potential hydrological drivers of changes in temperature extreme scaling by performing focused investigations over the Mediterranean and Southern African regions. Our results show substantial reductions in scaling of temperature extreme intensity after reaching net-zero CO₂ emissions over nearly all land regions, however, scaling changes are dependent on the cumulative emissions prior to reaching net-zero CO₂. Temperature extreme scaling reductions after net-zero CO₂ are also regionally dependent, and the regional magnitudes of scaling reductions tend to favor mid-latitude land in the Northern Hemisphere relative to tropical and Southern Hemispheric land masses. From focused investigations over the Mediterranean and Southern African regions, we find that changes in atmospheric circulation and local precipitation may play a major role in determining the sign and magnitude of changes in temperature extremes after net-zero CO₂ emissions.