The Multi-dimensional Nature of the Impact of Severe Heat Waves

Severe heat waves can have profound impacts on human and natural systems. However, the root causes of these impacts may not be due to high temperatures alone. The relative humidity and wind speed magnitude are also critical factors in the reaction of human beings to excess heat. This multidimensional nature of the impact of severe heat waves is generally compressed into one-dimensional measures of heat stress, if it is considered at all. We explore this multi-dimensional structure of heat waves through four case studies in Europe, Russia, Brazil and California that had severe human health consequences. We find detectible human influences that increase the likelihood of these four events due to anthropogenic climate change. We also project the further increase in the future likelihood of these events in a multi-dimensional sense. Figure Caption:Hourly characteristics of the summer 2010 heatwave at the Moscow weather station during the period June 21 to August 20 based on the HadISD data. Top: Heat Index. Middle: Surface air temperature. Bottom: Relative humidity. On the Heat Index plot, the yellow line indicates a caution health advisory, the orange line indicates an extreme caution health advisory.