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Climate change has been and will be accompanied by widespread changes in surface temperature. It is clear that these changes include global-wide increases in mean surface temperature and changes in temperature variance that are more regionally-dependent.sup.1-3. It is less clear whether they also include changes in the persistence of surface temperature. This is important as the effects of weather events on ecosystems and society depend critically on the length of the event. Here we provide an extensive survey of the response of surface temperature persistence to climate change over the twenty-first century from the output of 150 simulations run on four different Earth system models, and from simulations run on simplified models with varying representations of radiative processes and large-scale dynamics. Together, the results indicate that climate change simulations are marked by widespread changes in surface temperature persistence that are generally most robust over ocean areas and arise due to a seemingly broad range of physical processes. The findings point to both the robustness of widespread changes in persistence under climate change, and the critical need to better understand, simulate and constrain such changes. A survey of climate change simulations from different models indicates widespread changes in surface temperature persistence under global warming that may be attributable to a broad range of physical processes., Author(s): Jingyuan Li [sup.1] , David W. J. Thompson [sup.1] [sup.2] Author Affiliations: (1) Department of Atmospheric Science, Colorado State University, Fort Collins, USA (2) School of Environmental Sciences, University [...]

We compare insights provided by local and large‐scale perspectives of extreme heat events in ERA5 near‐surface temperature data. Heat waves where temperatures exceed four standard deviations about the climatological‐mean are expected less than once a century locally but occur roughly once every 10 days somewhere in the Northern Hemisphere midlatitudes. The high frequency of occurrence indicated by the hemispheric perspective is not well represented by normal statistics because it strongly depends on the shapes of the local temperature distributions. The large effective sample size afforded by the hemispheric perspective provides robust evidence of trends in the frequency of occurrence of extreme heat events integrated over the Northern Hemisphere. It also confirms that trends in heat events summed over the hemisphere can be explained by changes in mean temperature alone. Plain Language Summary: Extreme events can be studied from local and large‐scale perspectives. The two perspectives provide different insights into the likelihood of extreme events. For example, several notable recent heat waves in the Northern Hemisphere exceeded four standard deviations about the long‐term climatology. Locally, such events are expected less than once every century. But based on high spatial resolution temperature data, such events occur somewhere in the Northern Hemisphere roughly once every 10 days. The increased likelihood of extreme heat events when summed over the hemisphere is not well represented by normal statistics because it is strongly dependent on the shapes of the temperature distributions. The large effective sample size afforded by the hemispheric perspective is important, as it provides a robust estimate of the influence of climate change on the frequency of occurrence of heat events. The hemispheric perspective confirms previous findings that long‐term trends in extreme heat events summed over the Northern Hemisphere can be explained by recent increases in mean temperature. Key Points: Heat events expected less than once every century locally occur roughly once every 10 days somewhere in Northern Hemispheric midlatitudesHemispheric incidence is underestimated by a factor 10 by normal statistics and strongly influenced by the shape of frequency distributionsThe large sample size of the hemispheric perspective clarifies the key role of mean temperature in driving observed trends in heat events [ABSTRACT FROM AUTHOR]