Over the past four decades, droughts have become increasingly severe and widespread across the globe. While changing rainfall patterns are often blamed, a growing body of research reveals that another key factor is at play: the atmosphere itself is becoming thirstier. This phenomenon, known as atmospheric evaporative demand (AED), describes how much moisture the atmosphere “wants” to pull from land and vegetation. A new study published in Nature shows that AED is responsible for approximately 40% of the rise in global drought severity from 1981 to 2022.
To understand AED, imagine rainfall as income and evaporative demand as spending. Even if rainfall remains steady, an increase in AED leads to a water deficit — a drying imbalance where more moisture is taken from soils, rivers, and plants than is replenished. This process is intensified by rising global temperatures, which increase heat, sunlight, wind, and aridity — the meteorological factors that drive AED.
The research team used a globally recognized drought index that incorporates both rainfall and AED to assess when and where droughts worsened, and to what extent this worsening could be attributed to a thirstier atmosphere. Their findings reveal that AED not only intensifies existing droughts but also expands the areas affected by drought. From 2018 to 2022, the land area experiencing drought increased by 74%, and 58% of that expansion was directly linked to rising AED.
The year 2022 emerged as the most drought-stricken in more than 40 years. Over 30% of the Earth’s land surface experienced moderate to extreme drought conditions. In Europe and East Africa, the droughts were especially severe, with AED playing a major role in intensifying drying conditions — even in places where rainfall had not significantly declined. The impacts were wide-ranging: reduced river flows disrupted hydropower generation, crop yields dropped due to water stress, and many cities faced water shortages. This created profound pressure on agriculture, energy, and water supply systems, threatening economic stability and livelihoods.
The study emphasizes the importance of considering AED in drought forecasting and adaptation planning. Traditional approaches that focus solely on rainfall may overlook the atmosphere’s increasing demand for water, leading to an underestimation of drought risk. As global temperatures continue to rise, AED is expected to increase further, exacerbating drought conditions in already vulnerable regions such as western and eastern Africa, southern Australia, and the southwestern United States.
To adapt effectively, policymakers must identify the dominant drought drivers in each region. Where declining rainfall is the main issue, strategies should focus on water storage and conservation. But where AED is the primary driver, solutions must address evaporative losses and plant water stress — through techniques such as planting drought-resistant crops, improving irrigation efficiency, enhancing soil health, and restoring natural landscapes to retain moisture.
In sum, understanding and addressing AED is critical to building climate resilience. Ignoring it means underestimating both the severity and reach of future droughts — a costly mistake in an increasingly water-stressed world.
https://www.sciencealert.com/our-atmospheres-growing-thirst-is-a-hidden-cause-of-worsening-droughts