Beyond global mean temperature: increasing asymmetry of global warming in past and future climate change

Abstract

Global surface warming is recognized for its spatial asymmetry, which drives the complexity of climate change impacts. However, solely relying on average surface temperature change (ΔTmean) as an indicator of climate change may obscure this asymmetry. Here, going beyond ΔTmean, we quantify the long-term change in global warming asymmetry and its implications for climate mitigation. Results reveal a significant increase in warming asymmetry (0.18–0.29 °C3/decade) since 1900. Among 58 IPCC reference regions, the Arctic Ocean, Northwest North America, and Russian Regions contribute only 48% of this trend, with other Northern Hemisphere mid-high latitudes accounting for an additional 35%. Climate models project an emission-dependent nonlinear acceleration of warming asymmetry, with trends under SSP 5-8.5 being approximately 3–8 times greater than those under SSP2-4.5 and SSP1-2.6. Consequently, the global surface temperature change deviates from its original Gaussian distribution toward a highly skewed bimodal distribution. This increasing asymmetry implies a widening “divergence” within the climate system that is dependent on emission levels, including the gap between the ΔTmean and those observed across the majority of regions. Without rigorous emission reductions, this gap could foster cognitive biases in public awareness toward climate change, undermining public acceptance of climate mitigation policies.