Droughts are usually blamed on a lack of rain, but a team led by researchers at the School of Geography and the Environment has shown that there'ssomething else at work: the atmosphere itself is demanding more water out of the soil, rivers, and plants.

Atmospheric Evaporative Demand (AED) acts like an invisible sponge, soaking up moisture faster than it can be replaced, which canincrease water stress, particularly for plants. As the world gets hotter because of climate change, AED is rising - and it'scausing more severe drought events eveninwet regions.

The new study - 'Warming accelerates global drought severity', published in Nature - takes a close look at how much AED is responsible forthe worsening droughts happening all around us.

A new way to measure drought's growing danger

This work shows that including AED in drought monitoring, rather than relying on precipitation alone, is essential for better managing risks to agriculture, water resources, energy, and public health. Given projected climate changes, especially rising temperatures, the impact of AED is expected to intensify.

Dr Solomon Gebrechorkos

Until now, no one had measured AED's global impact using real-world observations - making it harder to predict and preparefor droughts. This study used a set of high-resolution data covering more than a century andapplied advanced methods to track how AED has increased and how much worse it has madedroughts.

Dr Solomon Gebrechorkos explained: 'We face a big challenge. There'sno direct way to measure how 'thirsty' the atmosphere is over time. So we used high-resolution climate data identifiedthrough a comprehensive global evaluation and applied the most advanced models for atmospheric evaporative demand- models that account for multiple climate variables, not just temperature. We also refined the methodological approach to improve accuracy.

'By doing so, we were able to generate a much clearer picture of how AED has evolved globally. We also identifiedregions most affected by this rising demand - an area spanning large parts of the world.

'This work shows that including AED in drought monitoring, rather than relying on precipitation alone, is essential for better managing risks toagriculture, water resources, energy, and public health. Given projected climate changes, especially rising temperatures, the impact of AED is expected to intensify.

'We need to act now by developing targeted socio-economic and environmental adaptation strategiesand improved early warning and risk management systems.Many affected areas are already struggling to cope with severe drought.'

Understanding drought in a warming world

We need to act now by developing targeted socio-economic and environmental adaptation strategies and improved early warning and risk management systems. Many affected areas are already struggling to cope with severe drought.

Dr Solomon Gebrechorkos

This research changes how we think about drought. It shows that it'snot just rainfall that matters - how much water the atmosphere demands isjust as important. As the planet keeps warming, AED will likely keeprising, drying out landscapes faster than rain can keep up, dramatically increasing plant water stress and impacting plant carbon uptake.

The findings suggest that future research needs to focus much more on how evaporation and atmospheric demand interact with water supplies, not just rainfall patterns. Scientists will also need to study how farmers, cities, and ecosystems can adapt to a world where the atmosphere constantly demands more moisture.More studies focused on climate drivenfluctuations in AED will also improve drought prediction.

Read 'Warming accelerates global drought severity' in Nature.