OSLO Hot weather extremes have increased around the world in the past 15 years despite a slowdown in the overall pace of global warming, a study showed on Wednesday.
Heat extremes are among the damaging impacts of climate change as they can raise death rates, especially among the elderly, damage food crops and strain everything from water to energy supplies.
"Observational data show a continued increase of hot extremes over land during the so-called global warming hiatus," scientists in Switzerland, Australia and Canada wrote in the journal Nature Climate Change.
A Russian heatwave in 2010 killed more than 55,000 people and a 2003 European heatwave killed 66,000. Pakistan recorded a temperature of 53.5 degrees Celsius (128 Fahrenheit) in 2010, the highest in Asia since 1942.
The average pace of warming at the planet's surface has slowed from the 20th century in what scientists link to factors such as absorption of more heat by the oceans, more sun-dimming pollution or volcanic eruptions.
This hiatus has heartened those who doubt that governments need to make big, urgent investments to shift from fossil fuels towards renewable energies. Almost 200 nations have agreed to work out a deal by the end of 2015 to combat climate change.
Wednesday's report found that the area of the world's land surface with 10, 30 and 50 extreme heat days a year had risen since 1997 from a 1979-2010 average, sometimes more than doubling, with big swings from year to year. Strongest gains were in the Arctic and mid-latitudes.
It was unclear why heat extremes had continued rising despite the hiatus. One possibility was that the oceans had soaked up heat from the atmosphere and slowed overall global warming, even as the land had been exposed to extremes.
"There is no reason to expect the (trend towards more hot extremes) to stop," lead author Sonia Seneviratne, of the Institute for Atmospheric and Climate Science at ETH Zurich, told Reuters.
The report follows other signs of more extreme weather as greenhouse gas emissions rise to new peaks.
A World Meteorological Organization (WMO) review last year showed that 56 countries reported a hot temperature record from 2001-10, while just 14 reported a new cold record.
England had a record 38.5 C (101.3F) in 2003, while northern Ireland had a record low -11.3 C (11.7 F) in 2010.
In Geneva, Michel Jarraud, head of the WMO, told a meeting on Tuesday that 13 of the 14 warmest years on record had been since 2000. "We are not seeing what I would call a pause in global temperature increases," he said.
(Reporting By Alister Doyle; Editing by Janet Lawrence)
Our top photos from the last 24 hours.