Nearly all the world’s major disasters over the past 20 years can be blamed on weather, with an estimated cost of $US250-$350 billion ($345-$414 billion) each year, according to a United Nations report.

And the number of weather-related disasters is increasing, up 14% over the past decade to average 335 a year. The frequency has almost doubled since 1985-95.

While scientists cannot calculate how much is due to climate change, predictions of future extreme weather suggest the increasing rate of catastrophes will continue.

The findings feature in a report from the UN Office for Disaster Risk Reduction and the Belgium-based Centre for Research on the Epidemiology of Disasters.

The report, spanning 20 years, says 606,000 lives have been lost, 87 million homes damaged or destroyed and 4.1 billion people adversely affected due to weather in the period.

It says 90% of major disasters have been caused by 6457 recorded floods, storms, heatwaves, droughts and other weather events.

The US had the most disasters with 472, while China recorded 441, India 288, Philippines 274 and Indonesia 163.

Asia bore the brunt of the impacts, with 332,000 deaths and 3.7 billion people affected.

Floods have accounted for 47% of all disasters in the past 20 years, killing 157,000 people and affecting 2.3 billion more, 95% of them in Asia.

The report says better flood control is a “low-hanging fruit” in terms of mitigation policy, since affordable and effective technologies exist, including dams, dykes, mobile dykes and early-warning systems.

Storms were the deadliest weather-related disasters, killing 242,000 people – 40% of global weather-related deaths. About 89% of these deaths were in lower-income countries.

The report says to reduce risk, two critical factors must be considered: population growth will put more people in harm’s way, and uncontrolled building on flood plains and storm-prone coastal zones will increase human vulnerability.

UN Office for Disaster Risk Reduction Head Margareta Wahlström says reducing greenhouse gas emissions would help reduce disasters losses.

“For now, there is a need to reduce existing levels of risk and avoid creating new risk by ensuring public and private investments are risk-informed and do not increase the exposure of people and economic assets to natural hazards on flood plains, vulnerable low-lying coastlines or other locations unsuited for human settlement,” she said.