![]() ![]() While data availability limits our analysis to begin in 1950, we find that trends in the spatially consistent Berkeley Earth 18 observational dataset match well with common regions between the previously used quasi-global HadGHCND 19 dataset and Berkeley Earth is thus useful in furthering our understanding of global and regional changes in heatwaves. An all-inclusive and consistent assessment is imperative for establishing confidence in the general consensus suggested by previous disparate studies, as well as being an integral component in accurately assessing the occurrence of and changes in heatwave impacts. This undermines a comprehensive understanding of how heatwaves have changed at regional and global scales. However, all relevant studies have employed diverse metrics, analysed a subset of heatwave characteristics over selected regions, and/or used different extreme thresholds over varying time periods. There is a general consensus that the intensity, frequency and duration of heatwaves have increased in the observational record, both regionally and globally 1, 13, 14, 15, 16, 17. Additionally, there are numerous ways to define each characteristic, a likely consequence of their expansive impacts as well as potential limitations of the datasets from which they are assessed. There are multiple characteristics to heatwaves, including their intensity, frequency, duration, timing and spatial extent. These impacts will increase under enhanced global warming, where more rapid heatwave trends will likely produce more severe and possibly irreversible impacts in some sectors 9, 10, 11, 12. The inequality of heatwave impacts has been assessed 5, 9, adversely affecting developing nations due to a lack of adaptive capacity, as well as varying cultural constraints. There are many adverse impacts of heatwaves, including on human health 2, agriculture 3, 4, workplace productivity 5, wildfire frequency and intensity 6, and public infrastructure 7, 8. Our results provide comparable regional observed heatwave trends, on spatial and temporal scales necessary for understanding impacts.ĭefined as prolonged periods of excessive heat 1, heatwaves are a specific type of extreme temperature event. ![]() Trends in heatwave frequency, duration and cumulative heat have accelerated since the 1950s, and due to the high influence of variability we recommend regional trends are assessed over multiple decades. A measure of cumulative heat shows significant increases almost everywhere since the 1950s, mainly driven by heatwave days. In almost all regions, heatwave frequency demonstrates the most rapid and significant change. Here, using the Berkeley Earth temperature dataset and key heatwave metrics, we systematically examine regional and global observed heatwave trends. Until now a comprehensive assessment of regional observed changes was hindered by the range of metrics employed, underpinning datasets, and time periods examined. Understanding regional heatwave trends has critical implications for the biophysical and human systems they impact. Heatwaves have increased in intensity, frequency and duration, with these trends projected to worsen under enhanced global warming. ![]()
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