Global droughts worsen as warming atmosphere intensifies water stress

A comprehensive international study has found that human-induced warming has dramatically intensified drought severity across the globe over the past four decades. Published in Nature under the title “Warming accelerates global drought severity,” the research presents an alarming account of how atmospheric evaporative demand (AED), the atmosphere’s thirst for water, has contributed to escalating drought trends between 1981 and 2022.

The team, led by Solomon H. Gebrechorkos from the University of Oxford and comprising researchers from top climate institutions worldwide, developed high-resolution datasets combining precipitation and AED data. Their findings reveal that AED, driven largely by global warming, is now responsible for an estimated 40% of the global trend toward more severe droughts - a figure that rises to more than 50% in regions like Australia and Africa.

How much is climate warming amplifying drought?

The study provides the most extensive observational evidence to date showing that AED, not just reduced rainfall, is a major factor behind increasing drought severity. By analyzing multiple datasets (CHIRPS, MSWEP, GLEAM, hPET, ERA5, and CRU-TS), the researchers constructed four high-resolution global drought indices using the Standardized Precipitation Evapotranspiration Index (SPEI). These indices were applied across six-month timescales to identify key metrics such as drought magnitude, duration, frequency, and extent.

Their analysis showed a significant decline in global SPEI values over the study period, with an observed trend of −0.0055 z-units per year, signifying worsening drought conditions. Correspondingly, the area affected by droughts increased by 0.36% per year, with even steeper rises for severe and extreme droughts.

Crucially, when AED was fixed at its historical climatological average (AEDclm), the simulated drying trend nearly vanished. Conversely, when precipitation was held constant and AED allowed to vary, the drying trend became three times more negative than observed. This clearly demonstrated that rising AED alone, driven by higher temperatures and increased vapor pressure deficit, has become a dominant force intensifying drought conditions worldwide.

Which regions are worst hit and why?

Regionally, the impact of AED on drought was found to be most severe in Africa, Australia, the western United States, and southern South America. In these areas, AED accounted for up to 65% of the worsening drought trend between 1981 and 2022. Australia showed a 119% increase in drought-affected area in the last five years alone, while parts of the western U.S. and southern South America experienced increases of 141% and 163% respectively when compared to the 1981–2017 baseline.

Even typically wet regions are not immune. Europe saw 82% of its landmass under drought conditions in 2022, with nearly half experiencing moderate to severe drought. This year set a new record globally, with 30% of the Earth’s land area affected by moderate to extreme droughts, 42% of which was directly attributable to heightened AED levels.

The research revealed that precipitation deficits alone cannot explain the extent of recent droughts. For instance, in Europe, streamflow and soil moisture anomalies in 2022 deviated so sharply from historical patterns that AED, not just rainfall decline, was identified as the principal driver. AED intensified drought through mechanisms like increased evapotranspiration and reduced latent heat fluxes from soils and plants, forming a feedback loop that worsens warming and drying.

What does this mean for future drought risk and policy?

The data confirms that droughts are not only becoming more frequent and severe but are also expanding spatially and intensifying in magnitude, particularly over the past five years. This pattern is expected to persist and likely worsen under continued warming scenarios.

While precipitation remains the dominant contributor to global drought trends (about 60%), the contribution of AED is both statistically and practically significant. In some dryland regions, AED's impact may even outweigh that of declining rainfall. The role of AED in driving ecological drought, impacting vegetation, agriculture, and water systems, is particularly concerning.

This research also marks a methodological advance. By isolating the roles of AED and precipitation through comparative modeling (observed vs. climatological inputs), it reduces previous uncertainties associated with drought trend assessments and strengthens the attribution to anthropogenic climate change.

The authors emphasize the need for urgent adaptation measures, including water resource planning, climate-resilient agriculture, and early warning systems that integrate AED trends into drought forecasting. Without such interventions, societies around the globe, especially in vulnerable regions, face escalating risks of water scarcity, food insecurity, biodiversity loss, and economic instability.