Abstract
Extreme heat events in the Great Lakes Basin (GLB) region of eastern North America are expected to increase in concert with greenhouse gas (GHG) induced global warming. The extent of this regional increase is also influenced by the direct effects of the Great Lakes themselves. This paper describes results from an ensemble of dynamically downscaled global warming projection using the Weather Research and Forecast (WRF) regional climate model coupled to the Freshwater Lake (FLake) model over the Great Lakes region. In our downscaling pipeline, we explore two sets of WRF physics configurations, with the initial and boundary conditions provided by four different fully coupled Global Climate Models (GCMs). Three time periods are investigated, namely an instrumental period (1979–1989) that is employed for validation, and a mid-century (2050–2060) and an end-century (2085–2100) periods that are used to understand the future impacts of global warming. Results from the instrumental period are characterized by large variations in climate states between the ensemble members, which is attributed to differences in both GCM forcing and WRF physics configuration. Results for the future periods, however, are such that the regional model results have good agreement with GCM results insofar as the rise of average temperature with GHG is concerned. Analysis of extreme heat events suggests that the occurrence rate of such events increase steadily with rising temperature, and that the Great Lakes exert strong lake effect influence on extreme heat events in this region.
Highlights
Record breaking extreme heat events have been occurring more frequently around the world in recent years
This is the case for Weather Research and Forecast (WRF) simulations forced with Coupled Model Intercomparison Project Phase 5 (CMIP5) models, whereas WRF results forced with Community Earth System Model version 1 (CESM1) show the smallest differences with the Global Climate Models (GCMs) data
This persistence in the bias of jet stream position indicates that the base state of climate for each CMIP5 member of the ensemble is likely unchanged during future projection periods, and the difference in model results are more related to the change in greenhouse gas (GHG) concentration toward the end of twenty-first Century
Summary
Record breaking extreme heat events have been occurring more frequently around the world in recent years. Some, such as the extreme heat events over Europe in 2019 (Vautard et al, 2020) and over western North America in 2021 (Philip et al, 2021) were especially severe, causing significant loss of life and property. This trend of increasingly active heat events has attracted a great deal of attention from the public, businesses and policy makers. The purpose of the present paper is to begin a discussion on the expected frequency of occurrence of extreme heat events in the GLB in the future
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