Droughts became 40 per cent more severe over past 40 years, study finds

New Delhi, Jun 5 (PTI) Rising temperatures, driven by climate change, is increasing the atmosphere's 'thirst', making droughts around the world 40 per cent more severe over the past 40 years, according to a new study.

Researchers, including those at the University of California-Santa Barbara, US, explained that the atmosphere is becoming warmer, thereby increasing its capacity to hold moisture -- atmospheric evaporative demand -- and making droughts more severe, even in places where rainfall has stayed the same.

"Drought is based on the difference between water supply (from precipitation) and atmospheric water demand. Including the latter reveals substantial increases in drought as the atmosphere warms," Chris Funk, director of the Climate Hazards Center at the University of California-Santa Barbara, said.

The findings published in the journal Nature indicate that atmospheric evaporative demand is playing an "increasingly important role in driving severe droughts", with the tendency likely to continue in a warmer future, the authors said.

Few studies have measured how atmospheric evaporative demand has impacted the world using real-world observations, making it harder to predict and prepare for droughts.

"We face a big challenge. There's no direct way to measure how 'thirsty' the atmosphere is over time," lead author Solomon Gebrechorkos, a hydro-climatologist at the University of Oxford, UK, said.

"So, we used high-resolution climate data, identified through a comprehensive global evaluation, and applied the most advanced models for atmospheric evaporative demand -- models that account for multiple climate variables, not just temperature," Gebrechorkos said.

Analysing data from 1901-2022, the researchers found that atmospheric evaporative demand has increased faster than precipitation rates, suggesting an "alarming tendency towards drier conditions".

"Here, by developing an ensemble of high-resolution global drought datasets for 1901–2022, we find an increasing trend in drought severity worldwide. Our findings suggest that AED (atmospheric evaporative demand) has increased drought severity by an average of 40 per cent globally," the authors wrote.

Funk said, "Most of us are familiar with how air temperatures are increasing rapidly, but most people may not realise the connections between this warming and the desiccating influence of the atmosphere." In warm areas, raising the temperature by just a couple of degrees can dramatically increase the atmosphere's ability to draw moisture from crops, rangelands and forests, he added.

The study also found that over the past five years, areas experiencing drought have grown by 74 per cent on average, compared with 1981-2017 -- and atmospheric evaporative demand contributed to 58 per cent of this increase.

The year 2022 was record-breaking, with 30 per cent of the world's land area affected by moderate and extreme droughts, 42 per cent of which was attributed to increased atmospheric evaporative demand, it said.

Datasets, such as the Multi-Source Weighted-Ensemble Precipitation (MSWEP), were used to analyse precipitation, while those, including the Global Land Evaporation Amsterdam Model (GLEAM), were used to measure atmospheric evaporative demand. PTI KRS KRS OZ MPL MPL