Robust increases in severe thunderstorm environments in response to greenhouse forcing

Abstract

Although severe thunderstorms are one of the primary causes of catastrophic loss in the United States, their response to elevated greenhouse forcing has remained a prominent source of uncertainty for climate change impacts assessment. We find that the Coupled Model Intercomparison Project, Phase 5, global climate model ensemble indicates robust increases in the occurrence of severe thunderstorm environments over the eastern United States in response to further global warming. For spring and autumn, these robust increases emerge before mean global warming of 2°C above the preindustrial baseline. We also find that days with high convective available potential energy (CAPE) and strong low-level wind shear increase in occurrence, suggesting an increasing likelihood of atmospheric conditions that contribute to the most severe events, including tornadoes. In contrast, whereas expected decreases in mean wind shear have been used to argue for a negative influence of global warming on severe thunderstorms, we find that decreases in shear are in fact concentrated in days with low CAPE and therefore do not decrease the total occurrence of severe environments. Further, we find that the shift toward high CAPE is most concentrated in days with low convective inhibition, increasing the occurrence of high-CAPE/low-convective inhibition days. The fact that the projected increases in severe environments are robust across a suite of climate models, emerge in response to relatively moderate global warming, and result from robust physical changes suggests that continued increases in greenhouse forcing are likely to increase severe thunderstorm occurrence, thereby increasing the risk of thunderstorm-related damage.severe weather | CMIP5 | GCM | hazards

Changing volatility of U.S. annual tornado reports

“…Most climate change studies have focused on trends in environments favorable to severe thunderstorms, generally finding upward trends over the U.S. [Trapp et al, 2009;Diffenbaugh et al, 2013]. Sander et al [2013] did find an increase in the variance of both large loss events and environments favorable to severe thunderstorms between the periods 1970-1989 and 1990-2009, with convective available potential energy playing an important role.…”

Indiana’s Past & Future Climate: A Report from the Indiana Climate Change Impacts Assessment

“…Scientists look at the "ingredients, " such as instability and vertical wind shear, that can lead to thunderstorms and tornadoes. Those ingredients are expected to increase under a changing climate (Diffenbaugh et a., 2013), but that doesn't necessarily mean that they will lead to increased storm activity or more severe storms.…”

Future Change of Tornadogenesis-Favorable Environmental Conditions in Japan Estimated by a 20-km-Mesh Atmospheric General Circulation Model

“…Diffenbaugh et al (2013), who projected future changes of severe thunderstorms in the United States based on the fifth phase of the Coupled Model Intercomparison Project (CMIP5), a global climate model ensemble experiment, showed an increase in the frequency of severe thunderstorms exceeding 100 % (more than twice the frequency of the present-day climate) in Tornado Alley and the Atlantic coastal region during MAM and JJA. In contrast, according to Lee (2012) and Diffenbaugh et al (2013), some ensemble members indicate a decrease of severe thunderstorm frequency in the southern part of Tornado Alley during JJA. However, our result for the distribution of the future/present ratios of FSCs exceeding 1.5 in tornadogenesis possibilities in Tornado Alley and the Atlantic coastal region (Fig.…”