UC Irvine

Global temperatures have risen 0.6 degrees Celsius in the 20th century and have been projected to rise an additional 1.0-3.7 degrees Celsius in the 21st century depending on the emissions scenario. Climate records also show that drought events have been occurring more frequently during high temperature anomalies. Previous studies show strong feedbacks between drought conditions and surface temperatures, which prompted the question of whether drought conditions are experiencing larger temperature increases in comparison to the average climate. The objective of this study was to investigate whether droughts have been warming faster than average climate conditions in the contiguous United States. Using gridded observations and climate models, we compared temperatures during different categories of drought severity on a monthly scale and mapped areas displaying an escalation of temperature with stricter definitions of drought. We observed a historical shift of warming temperatures during dry months in Southern and Eastern regions between the early and late halves of the 20th century. Future projections also showed a larger warming shift during dry months in the Southern US between the 20th and 21st centuries. In the climate projections, the higher temperature shift was mostly attributed to the summer months. The summer associated temperature shift is rooted in preceding winter and spring precipitation, which influence the surface energy balance in regions with moderate climate. These mid-latitude temperature shifts associated with dry conditions are an important piece in understanding and deconstructing climate conditions in a rapidly changing environment.