Economic losses caused by climate-related disasters have soared by about two and a half times in the last twenty years, the United Nations has said.

From 1998 to 2017, direct losses from all disasters totalled $2.9 trillion, of which 77% was due to extreme weather that is intensifying as the world warms, the UN Office for Disaster Risk Reduction said in a report.

That compares with overall losses of $1.3tn from 1978 to 1997, 68% of that accounted for by climate and weather hazards, including storms, floods and droughts.

"We can see that climate change is playing an increasingly important role in driving up disaster losses around the world, and that probably will be the case in the future as well," Ricardo Mena, an official at the Geneva-based UNISDR, said.

The findings were released as Michael, a Category Four hurricane, rumbled towards the Gulf Coast of Florida, in the latest storm to threaten vast destruction across the eastern US.

On Monday, climate scientists warned that if global average temperatures rise more than 1.5 degrees Celsius above pre-industrial times, it would lead to more suffering - especially among the world's poorest.

The planet has already heated up by about 1 degree Celsius.

Climate change is increasing the frequency and severity of extreme weather, and disasters will continue to set back sustainable development, the UNISDR report warned.

Climate-related disasters accounted for about 90% of the 7,255 major disasters between 1998 and 2017, most of them floods and storms, it said.

Losses were greatest in the United States at $945bn, followed by China at $492bn and Japan at $376bn.

In the past two decades, 1.3 million people were killed and 4.4bn were injured, left homeless, displaced or required emergency help.

More than half the deaths were caused by 563 earthquakes and related tsunamis, said the report drawing on data from the Centre for Research on the Epidemiology of Disasters in Belgium.

Although rich countries shoulder the highest absolute economic losses, the report noted the disproportionate impact of disasters on low and middle-income countries.

People in poorer nations are seven times more likely to be killed by a disaster than in wealthier ones, Mr Mena told the Thomson Reuters Foundation.

In developing countries, economic losses are not analysed for many disasters, meaning the new data was just the "tip of the iceberg", he noted.