Climate change is more than average: contrasting trends in means versus trends in extremes in a warming climate

Keywords: climate change, climatology, extremes, extreme events, climate variability
Session Type: Virtual Paper Abstract
Day: Tuesday
Session Start / End Time: 3/1/2022 11:20 AM (Eastern Time (US & Canada)) - 3/1/2022 12:40 PM (Eastern Time (US & Canada))
Room: Virtual 71

Abstract

The mean global temperature is unequivocally rising. While means are easy to understand and convenient metrics to measure trends in a changing system, the calculation of averages casts aside mountains of valuable data; and by their very definition, averages are uneventful. Much more impactful on day-to-day life are the rarer extreme events. Intuitively, many would assume that with increasing averages, we would expect a clean shift of the distribution rightward, leading to more frequent, longer-lasting, and/or larger-scale extreme heat events, at the expense of these same attributes equally for extreme cold events. This research examines these assumptions with regard to temperatures in North America. While for the most part, these assumptions are correct, there are some important exceptions. Among them, despite rising autumn temperatures in northern Canada, extreme heat events have remained largely stable. Likely due to shifts in the timing of sea-ice freeze-up, the area has experienced significantly reduced temperature variability, which is leading instead to a substantial decrease in extreme cold events, with little change in heat events. In parts of the western US, even without a significant trend in autumn mean temperatures, there is a significant rise in extreme cold events accompanying increased variability. And, in the southern High Plains in summer, despite insignificant increases in average temperatures, increasing skewness to the distribution is nonetheless leading to a significant rise in heat events. These results suggest that larger-scale analyses of mere averages may overlook nontrivial regional-scale nuance in climatic trends.