Hot extremes amplified by low soil moisture

While temperatures are expected to rise in most regions of the world as a consequence of global warming, the amount by which hot extremes increase shows strong regional differences. In this study we examine the global patterns of where hot extremes are warming faster than the average temperatures, indicating where hot temperatures are becoming ‘more extreme’ relative to the average conditions, and what drives these changes.

We identify hot spots of accelerated warming of model-simulated hot extremes in Europe, North America, South America, and Southeast China, and these hot spots are robust across most state-of-the-art climate models. To identify potential drivers of the accelerated warming of hot extremes, we explore the environmental conditions on the exact dates when the heat extremes occur. We find that the global pattern of where hot extremes warm fastest is explained by changes in the surface energy fluxes consistent with drying soils in these hot spot regions.
 

Change in average temperature on the hottest day relative to change in local annual average temperatures.

However, the model-simulated patterns of accelerated warming of hot extremes, although consistent across most models, appear partly inconsistent with observations. This inconsistency suggests that future simulations of hot extremes may be unreliable, and indicates the necessity for a reevaluation of how climate models resolve the relevant terrestrial processes.
 

• Donat, M. G., A. J. Pitman, and S. I. Seneviratne (2017), Regional warming of hot extremes accelerated by surface energy fluxes, Geophys. Res. Lett., 44, 7011–7019, doi:10.1002/2017GL073733.
• Photo by Julien Lavallée on Unsplash