Increasing trends in regional heatwaves

TLDR

Heatwaves have intensified, become more frequent and longer, and are projected to worsen, yet a comprehensive assessment of regional trends has been limited by diverse metrics, datasets, and time periods. The study systematically examines regional and global observed heatwave trends using the Berkeley Earth temperature dataset and key heatwave metrics. The authors analyze Berkeley Earth temperature data with key heatwave metrics to assess regional and global trends. Heatwave frequency has increased most rapidly, cumulative heat has risen significantly since the 1950s, and the study recommends multi‑decadal assessments, providing comparable regional trends for impact analysis.

Abstract

Abstract Heatwaves have increased in intensity, frequency and duration, with these trends projected to worsen under enhanced global warming. Understanding regional heatwave trends has critical implications for the biophysical and human systems they impact. Until now a comprehensive assessment of regional observed changes was hindered by the range of metrics employed, underpinning datasets, and time periods examined. Here, using the Berkeley Earth temperature dataset and key heatwave metrics, we systematically examine regional and global observed heatwave trends. In almost all regions, heatwave frequency demonstrates the most rapid and significant change. A measure of cumulative heat shows significant increases almost everywhere since the 1950s, mainly driven by heatwave days. 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. Our results provide comparable regional observed heatwave trends, on spatial and temporal scales necessary for understanding impacts.