Warming is changing the water cycle across the planet

Jan. 13 () –

The third consecutive year of La Niña intensified droughts in the Americas in 2022 and caused flooding in parts of Asia and Oceania, according to a groundbreaking report by the Global Water Monitor Consortium.

The report, led by researchers at the Australian National University (ANU), concludes that global warming is changing the water cycle throughout the planet, while warning that phenomena such as flash droughts will be more frequent in the coming years.

Lead author Professor Albert Van Dijk says the report offers a unique snapshot of global water availability.

“Typically, it takes many months to collect, collate, analyze and interpret this kind of data,” he said. it’s a statement Professor Van Dijk, from the ANU Fenner School of Environment and Society.

“By taking full advantage of the instruments on Earth-orbiting satellites and automating the entire process of data analysis and interpretation, our team has been able to reduce that time to a few days.”

The group combined water measurements made at thousands of ground and satellite stations to obtain updated information on precipitation, air temperature and humidity, soil water, river flows and volume of water in natural and artificial lakes.

On a global scale, in 2022 the water cycle was dominated by relatively warm ocean waters in the western Pacific and eastern and northern Indian Oceans. As a consequence, a severe heat wave occurred in South Asia at the beginning of the year, followed by a very wet monsoon which caused massive flooding in Pakistan.

In other places, such as Europe and China, extreme heat waves gave rise to so-called “flash droughts”, that is, droughts that develop a few months after severe heat waves, causing low river flows, agricultural damage, and forest fires.

The report shows that the air temperature over land in 2022 followed the long-term warming trend, while the air humidity is decreasing.

“This means that nature, crops and people will need more water to stay healthy, exacerbating the problem,” said Professor Van Dijk.

“It is a safe prediction that we will see more and more of these heat waves and flash droughts. We also see evidence of the impact of global warming on glaciers and the water cycle in cold regions, and indeed melting glaciers contributed to Pakistan floods. That will continue until those glaciers disappear.”

A key feature of 2022 was that it was the third consecutive year of La Niña. This caused flooding problems in Australia, but also deepened drought conditions in the western United States and parts of South America.

“It is not yet known if those three years of La Niña were a statistical fluke or the first signs of something more sinister,” said Professor Van Dijk.

“If La Niña or El Niño patterns are going to stick around longer in the future, that’s going to cause a lot of problems, with worse and longer droughts and worse floods alike.”

The report also offers an outlook for 2023, with relatively dry conditions indicating the possibility of intensifying or new droughts in parts of North and South America, Central Asia, China and the Horn of Africa. However, La Niña conditions are subsiding, so there is hope that water availability may soon return to more normal levels in some of those regions.

The Global Water Monitor is a joint initiative of several public and private research and development organizations that share the goal of providing free, fast, global information on climate and water resources.