“Disasters such as the Boscastle flooding [in Cornwall in 2004] are moving from being a once-in-100-year event to a once-in-20-year event.” As the atmosphere warms it stores more energy and can hold more water. “You will have heavier downpours in places that are not used to having them,” she said.
Peter Stott, head of climate monitoring at Britain’s Met Office, said that the results were consistent with the national forecaster’s predictions of the impact of the 0.7C increase in global temperature since pre-industrial times.
“We would expect the frequency of heatwaves and heavy rainfall events to continue increasing as the climate continues to warm,” he said. The probability of more events such as the 2003 heatwave in Europe, which killed 35,000 people, had “likely doubled as a result of human influence”, he said. “[They] could become considered the norm by the middle of this century.”
Munich Re’s analysis covered all weather disasters, not just those involving significant insured losses, and took account of population changes. It found that floods and landslides had trebled since 1980 and storms had doubled. The annual average number of disasters increased from 339 in the 1980s to 547 in the 1990s and 693 between 2000 and 2009.
Peter Hoppe, head of Munich Re’s geo risk research department, said bias was removed by measuring the change in reported earthquakes and tsunamis. These could not have been caused by human emissions and the 50 per cent rise recorded over the 30-year period was likely to have been the result of greater reporting of events. Using this benchmark the first 50 per cent of the increase in recorded floods and storms was discounted when producing the long-term trend.
He said insurers could no longer rely on long-term averages for predicting disasters and assumed an exponential increase in extreme weather.