Drought risk in the Anthropocene

Abstract

The summer of 2022 has seen remarkable hydrological conditions across much of the Northern Hemisphere. Europe has seen what could be the most severe drought conditions to hit the continent for more than 500 years [1], with exceptionally low water levels impacting navigation of inland waterways and leaving insufficient cooling water for power plants. French fire fighters struggled with wildfires on a dramatic scale. The Yangtze River in China reached historically low levels. In the Western USA, the drought has broken previous records for the driest 22-year period in the region since the year 800 CE [2], depriving farmers of water and further impacting fragile ecosystems in the Colorado River basin. Examining these various manifestations of drought reveals a series of interlinked phenomena that are examined in this themed issue of the Philosophical Transactions of the Royal Society. First, it is clear that droughts are profoundly humaninfluenced, and we expect them to be even more so in the future. The title of this themed issue—Drought risk in the Anthropocene—reflects the recognition that the Earth System is human-influenced to an extent that we are said to be living in a new geological era [3]. Droughts are a manifestation of the Anthropocene in a number of different senses. As the paper by Vicente-Serano et al. (Global drought trends and future projections) [4] explains, greenhouse gas emissions are driving some of the conditions that are making droughts more severe. Human influences both warm the planet and intensify contrasts between wet and dry conditions, and drought has been impacted particularly by increased evaporation linked to warming. Human