Abstract

Heatwaves are extreme weather events with significant impacts on natural ecosystems, human health, and socioeconomic systems. While global trends indicate an increase in the frequency, duration, and intensity of heatwaves due to climate change, regional studies are essential to understand local variations and impacts. This study aims to address the gap in knowledge regarding the evolution of heatwaves in Central Chile and California, two regions with similar Mediterranean climates but located in different hemispheres. We analyzed temperature data from meteorological stations in Central Chile and California over the past five decades. Using various heatwave definitions and indices, we quantified trends in heatwave frequency, duration, and intensity. We used statistical tests, such as linear regression and the Mann-Whitney U-test, to assess the significance and potential non-linear changes in these trends. Our analysis revealed consistent increases in the frequency, duration, and intensity of heatwaves in both regions. Notably, these trends have accelerated over the last two decades. For example, the number of heatwave events per year in Central Chile increased by approximately one event every five to six years (with p < 0.01). Similar trends were observed in California, although with some regional variations. The Mann-Whitney U-test indicated significant abrupt changes in heatwave behavior around 2010 in both regions. Our findings highlight the accelerating impact of climate change on heatwave characteristics in Central Chile and California, and indicate possible abrupt changes in heatwave behavior as a result of global warming. Our results contribute to the understanding of regional climate dynamics and underscore the need for adaptive measures to mitigate the adverse effects of increasing heatwaves. Further research is needed to explore the underlying mechanisms driving these changes and to develop effective adaptation strategies.