Decreasing subseasonal temperature variability in the northern extratropics attributed to human influence

Abstract

Changes in subseasonal temperature variability are linked with the altered probability of weather extremes and have important impacts on society and ecological systems. Earlier studies based on observations up to 2014 have shown a general decrease in subseasonal temperature variability over Northern Hemisphere extratropical land. However, these changes have been confined to specific regions and seasons, have limited statistical significance and human influence is yet to be determined. Here we show using up-to-date observations and climate model simulations that a human fingerprint, or pattern of change, in subseasonal variability has recently emerged over the Northern Hemisphere extratropics. The fingerprint features decreased near-surface air temperature variability over land in the high-northern latitudes in autumn, further extending into mid-latitudes in winter. Using large ensembles of single-forcing model experiments, we attribute the pattern of reduced temperature variability primarily to increased anthropogenic greenhouse gas concentrations, with anthropogenic aerosols playing a secondary role. Our results reveal that human influence is now detectable in hemispheric-wide day-to-day temperature variability and motivates research into the impacts of reduced temperature volatility on societal and ecological systems.