A Theory on Regional Impacts of Global Warming

Abstract

Although spatial patterns of the observed and projected global warming are uniform with some relatively small variability, the magnitude and even sign of the projected regional impacts on crop yields, transmission of infectious diseases, outdoor days, and deadly heat waves, among other phenomena, vary significantly between different regions. Here, we offer a theory explaining how an apparently uniform warming with small variability can produce significantly more diverse regional impacts. The natural phenomena behind these impacts are governed by temperature thresholds dictating how the phenomena nonlinearly react to surface temperature, defining optimal ranges. Depending on how the background temperature at any location compares to these thresholds, the nature of the regional impacts of global warming, in sign and magnitude, may vary significantly in space despite relatively uniform warming. Hence, the spatial variability of historical temperature distribution emerges as a significant determinant of some of the projected regional impacts of global warming.

Plain Language Summary

Global warming is causing a globally consistent upward trend in surface temperatures, but its effects vary widely by region. Some regions experience reduced crop productivity, increased risk of disease transmission, fewer favorable outdoor conditions, and more frequent extreme heat events, whereas others may experience less severe or even locally favorable conditions. Here, we propose a theory to explain why relatively uniform global warming can result in regionally divergent climate impacts. This theory proposes that the magnitude and direction of these impacts are governed by how global warming shifts local temperatures relative to thresholds specific to each type of temperature-sensitive phenomenon. Our results highlight the importance of historical temperature baselines in modulating the regional heterogeneity of climate change responses. This insight can guide better decisions to manage both risks and potential benefits.

Key Points

• Despite relatively uniform global warming, regional impacts exhibit significantly larger variability in both magnitude and direction
• Regional climate responses are modulated by how local temperatures compare to impact-specific temperature thresholds
• Historical temperature distributions help explain spatial variability in projected climate impacts