Deadly floods, cyclones and droughts are wreaking havoc as record-breaking temperatures change the way water moves around the world, scientists warn.
Water-related disasters killed thousands of people, displaced millions and caused losses exceeding $US550 billion in 2024, according to an international study released on Monday.
The outlook for 2025 signals the greatest risk of developing or deepening drought in western Australia, the Americas and southern Africa, while other areas could face greater flood risks.
Ongoing climate change increases the potential for flash floods, flash droughts, intense storms and heatwaves across many regions, according to the 2024 Global Water Monitor.
"But it's not on people's agenda until your house burns or washes away, or you don't have water coming out of the tap," lead author Professor Albert van Dijk told AAP.
Australia's experience with climate extremes, flash floods and bushfires makes us a little more resilient, Australian National University's Prof van Dijk said.
"But the extremes are also getting more extreme," he said, calling for better flood defences, more drought-resilient food production and water supplies and better early warning systems.
Half of the world's population - four billion people across 111 countries - experienced their warmest year yet amid a worsening trend of more intense and localised flash floods, prolonged droughts and record-breaking extremes, the report found.
"Heat is also a major issue for Australians," Prof van Dijk said, as climate extremes alter the world water cycle of how water gets from the sky to the land and back again.
"The unfortunate truth is that even if we stopped emitting greenhouse gases right now, we would still be stuck with climate change for several decades," he said.
The most damaging water-related disasters of the past year included flash floods, river floods, droughts, tropical cyclones and landslides including the devastation in Papua New Guinea's Enga Province in May.
The research team used data from thousands of ground stations and satellites orbiting the earth to capture insights on rainfall, soil moisture, river flows and flooding.
Air temperatures over land in 2024 were 1.2C warmer than at the start of the century, and about 2.2C higher than at the start of the Industrial Revolution.
The number of record-high monthly average temperatures in the 4687 river catchments worldwide was the highest in the 45-year record and 9.3 times the 1995 to 2005 average.
New records were set for annual maximum temperature in 34 countries and hot days in 40 countries.
The Australia West Coast and Lake Eyre basins were among the 21 river basins with record-high annual discharge values.
Twenty-eight countries had record-high annual minimum temperatures, while unusually high annual minimum temperatures were recorded in 16 countries including in Polynesia.
Four countries recorded record-low annual soil moisture levels, including Samoa.
Oceania also showed record surface water extent, or inundation, in Australia, New Zealand, Fiji, Tonga, Micronesia and Vanuatu.
Globally, the number of frost days was the lowest on record while annual minimum temperatures were increasing, especially in the tropics.
