Heatwaves are increasing in frequency and intensity the world over, an Australian weather researcher has found, with his warnings being run up to the United Nations as it prepares its next climate report.
The work of John Nairn, a pioneering researcher at South Australia's Bureau of Meteorology, is up for inclusion in the next report from the UN Intergovernmental Panel on Climate Change.
As debate grinds on in Doha over a global climate deal, Nairn is warning heatwaves present the most damaging threat to human life. A 2003 heatwave killed 70,000 people in Europe
, while in Australia a series of hot days in 2009 resulted in almost 400 fatalities
Nairn says heatwaves are increasing in severity and government policy is still woefully inadequate globally. While weather reports and government policies continue to focus on maximum temperatures during heatwaves, Nairn says the minimum is actually more important.
"Back in the 1950s, the number of days of heatwaves measured … five to six days being more common," Nairn said. "Now they're reaching up to about eight or nine days."
The number of separate heatwave incidents has steadily marched up by between 1-2% each decade since 1960. And general warm spells -- prolonged hot periods that do not reach the temperature threshold for heatwaves -- have also increased in frequency. "Warm spells, irrespective of season, were quite strong and particularly the minimum temperature. It doesn't matter what time of year, we're seeing runs of warm spells," he said.
The trend impacts the entire world but is most concentrated in tropical latitudes. "The research shows … mid-latitude Australia, which is the southern half of the continent, is showing the signal of both increasing warm spells and heatwaves, in all of the parameters -- amplitude, frequency and length of heatwaves," he said.
Nairn's research finds current definitions of heatwaves are incomplete, leading to ineffective government responses. The Bureau of Meteorology currently defines a heatwave as five consecutive days over 35 degrees, or three days over 40 degrees.
"1990 was when the bureau was challenged to give a definition by the media," Nairn said. "So they went out the back, scrambled around, came up with a relatively quick, tidy definition. Trouble is, when you get a 2009 event come along … it would turn out the minimum temperature is actually the most important temperature.
People need cool nights to recover from the heat of the day, Nairn says. A hot night doesn't give them a chance to recover, putting their health at risk.
Because heatwaves haven't been fully understood the bureau hadn't been able to give the government correct information -- which had led to poor outcomes according to Nairn. During the 2009 heatwave "anecdotal evidence was that a high proportion of the hospital admissions came pre-dawn". "And that was a pretty clear sign that people had been trying to cope, and they simply hadn't had enough recovery, and as the next warm day was kicking in they were beginning to fail," Nairn said.
"If you can't recover from the hot day as you prepare for the next hot day, you're carrying forward an extra quantum of heat that is going to be another brick in the wall that you're going to have to deal with. Renal, endocrine and cardiovascular systems in human beings [take] between two and six weeks to adjust to severe changes in temperature."
*This article was originally published at InDaily