ANU releases water report; shows global warming affecting water cycle

The third La Niña year in a row intensified existing droughts in the Americas, while causing floods in parts of Asia and Oceania, according to a first-of-its-kind report released today by the Global Water Monitor Consortium, led by researchers at The Australian National University (ANU).

The report found global warming is changing the water cycle across the planet, while also warning that events like flash droughts will become more frequent in the coming years.

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

“Normally, it takes many months for this kind of data to be collected, collated, analysed and interpreted,” Professor Van Dijk from the ANU Fenner School of Environment and Society said.

“By making the best possible use of satellite instruments orbiting the Earth and by automating the whole data analysis and interpretation process, our team has been able to reduce that time to a few days.”

The group combined water measurements made at thousands of ground stations and by satellites to produce up-to-date information on rainfall, air temperature and humidity, soil water, river flows and the volume of water in natural and artificial lakes.

Globally, in 2022 the water cycle was dominated by relatively warm ocean waters in the western Pacific and the eastern and northern Indian Ocean. As a result, a severe heatwave developed in South Asia early in the year, followed by a very wet monsoon that caused massive floods in Pakistan.

Elsewhere, in Europe and China, extreme heatwaves gave rise to so-called ‘flash droughts’ – droughts that develop within a few months following severe heatwaves, causing low river flows, agricultural damage and bushfires.

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

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

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

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

“The jury is still out on whether those three La Niña years were a statistical fluke or the first signs of something more sinister,” Professor Van Dijk said.

“If La Niña or El Niño patterns are going to stay around longer in future, that is going to cause a lot of trouble, with worse, longer droughts and worse floods alike.”

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