Global trends in the frequency and duration of temperature extremes

Anthropogenic climate change has affected the frequency and duration of extreme climate events, including extreme heat events (EHE) and extreme cold events (ECE). How the frequency and duration of both EHE and ECE have changed over time within both terrestrial and marine environments globally has not been fully explored. Here, we use detrended daily estimates of minimum and maximum temperature from the ERA5 reanalysis over a 70-year period (1950-2019) to estimate the daily occurrence of EHE and ECE across the globe. We measure the frequency and duration of EHE and ECE by season across years and estimate how these measures have changed over time. Frequency and duration for both EHE and ECE presented similar patterns characterized by low spatial heterogeneity and strong seasonal variation. High EHE frequency and duration occurred within the Antarctic during the austral summer and winter and within the Arctic Ocean during the boreal winter. High ECE frequency and duration occurred within the Nearctic and Palearctic during the boreal winter and the Arctic Ocean during the boreal summer. The trend analysis presented pronounced differences between frequency and duration, high spatial heterogeneity, especially within terrestrial environments, and strong seasonal variation. Positive EHE trends, primarily in duration within marine environments, occurred during the boreal summer within the mid-latitudes of the Northern Hemisphere and during the austral summer within the mid-latitudes of the Southern Hemisphere. The eastern tropical Pacific contained positive EHE and ECE trends, primary in duration during the boreal winter. Our findings emphasize the many near-term challenges that extreme temperature events are likely to pose for human and natural systems within terrestrial and marine environments, and the need to advance our understanding of the developing long-term implications of these changing dynamics as climate change progresses.