The Atmosphere’s Growing Thirst: A Key but Overlooked Factor in Intensifying Droughts

Droughts are becoming increasingly intense and widespread around the world—but declining rainfall isn’t the only reason. A lesser-known culprit is the atmosphere’s growing demand for water.

In a recent Nature study, my colleagues and I found that this increased “atmospheric thirst”—technically known as atmospheric evaporative demand (AED)—has driven around 40% of the worsening drought conditions observed between 1981 and 2022.

Think of it this way: if rainfall is your income and AED is your spending, even a steady income can’t prevent a deficit if your expenses keep rising. That’s the current reality—more water is being drawn from the land than it can sustainably give.

As global temperatures rise, the atmosphere pulls more moisture from soils, rivers, lakes, and vegetation. As a result, even in regions where precipitation hasn’t decreased significantly, drought severity is still increasing.

AED reflects how much moisture the air seeks from the Earth’s surface. The hotter, sunnier, windier, and drier the atmosphere, the higher its demand—regardless of how much rain falls.

That means many places experiencing similar rainfall to past years are now drying out faster and more completely. The increased atmospheric demand adds pressure in water-scarce moments, exacerbating stress on ecosystems and communities.

Our research shows that AED not only worsens current droughts but also increases their geographical reach. Between 2018 and 2022, the total global land area affected by drought expanded by 74%, and over half of that expansion—58%—can be attributed to increased AED.

The year 2022 stood out as the most drought-affected year in over 40 years. More than 30% of Earth’s land surface faced moderate to extreme drought. Europe and East Africa, in particular, saw severe impacts—mainly driven by a dramatic rise in AED, not necessarily by reduced rainfall.

In Europe, for instance, widespread drying led to falling river levels that disrupted hydropower production, agricultural losses from stressed crops, and water shortages in cities—putting immense pressure on infrastructure, farming, and energy systems.

To better understand these patterns, our team used high-resolution climate data, factoring in temperature, wind, humidity, and solar radiation—all variables that influence how much water the atmosphere pulls from land and plants. This allowed us to measure AED effectively—essentially quantifying how “thirsty” the air is.

With this information, we applied a globally accepted drought index that combines rainfall and AED. This helped us identify the timing, location, and causes of droughts. Most importantly, we could isolate the role of atmospheric demand in making droughts worse.

Looking ahead, the implications of rising AED are particularly concerning for drought-prone regions like western and eastern Africa, southern and western Australia, and the southwestern United States—where AED has contributed to over 60% of drought severity in the past 20 years.

If we ignore AED in drought planning and monitoring, we risk underestimating the challenges ahead. With global temperatures expected to continue rising, so will the frequency and severity of droughts. Preparing for this means acknowledging and planning around the atmosphere’s increasing thirst.

Understanding What Drives Droughts

Pinpointing the causes of drought in specific regions is crucial for effective climate resilience. AED needs to be a core part of drought monitoring, forecasting, and response.

Tailored strategies depend on whether rainfall decline or AED is the main driver. If rainfall is the issue, then the focus should be on water conservation and storage. But when AED is the dominant factor, solutions should tackle evaporative losses and plant water stress—through drought-resistant crops, efficient irrigation, soil improvement, and ecosystem restoration.

Our findings confirm that global warming is fueling a rise in AED, which in turn makes droughts more intense—even when rainfall hasn’t dropped. Failing to account for this growing atmospheric thirst puts communities, ecosystems, and economies at greater risk.

Read the original article on: Science Alert

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