Back in 2003 a heatwave centred in France killed over 70,000 people. Another which struck Moscow in 2010 killed 10,000. During the 2009 Black Saturday bushfires in Victoria 173 people tragically lost their lives from the fire. However, health authorities believe Victoria’s record-breaking heatwave may have contributed to the deaths of about another 374 people with the state’s death toll 62% higher than at same time in the previous year.
The elderly were worst affected, but the very young and those in frail health are also typically affected in events like this.
January 2017 was the hottest ever recorded in Sydney and Brisbane, and great swathes of the south-east endured temperatures that often exceeded 40°C for weeks on end. It was so hot that dairy cows dropped dead in the paddocks, according to a new article in the New Scientist (pay-walled). This year saw the mercury climb to 47°C in Sydney, the hottest in 79 years. However, by 2040 Melbourne and Sydney could be experiencing mega‑heatwaves with highs of 50°C:
- “Going out to 40 or 50 years, basically the summer we just had will be normal,” says Sarah Perkins-Kirkpatrick at the Climate Change Research Centre of the University of New South Wales (UNSW) in Sydney. “It hasn’t really sunken in yet in Australia.”
The absolute maximum for humans to survive is a ‘wet-bulb’ temperature of 35°C, that is 35°C with 100% humidity. Under these conditions healthy people will die within about six hours. If the temperature is 40°C, however, you only need 75% humidity for the same effect. So far on the planet this limit has only been approached once in habitated areas, as far as we know’, in Bandahr Mashar in Iran in 2015, when the mercury was 46°C with 50% humidity.
With warming of 6°C or more significant areas of the globe would become uninhabitable. Short of that heat will become increasingly problematic as the world warms. Camilo Mora of the University of Hawaii and his team have published a study which found already that 30 per cent of the world’s population experiences potentially deadly temperatures for at least 20 days every year. They found that this will rise to nearly 75 per cent by 2100 if we do little to limit greenhouse gas emissions.
His team found that there are 27 ways that heat can fatally affect the human body. One of the main ones is that your gut lining disintegrates, releasing the intestine’s contents into the bloodstream, thus triggering a catastrophic immune response which ends in major organ failure. Many heat deaths are simply recorded as a heart attack.
With 27 pathways to death, there are large variations between individuals in the body’s response to heat.
The body to a certain extent becomes accustomed to different levels of temperature. It take about a week to adjust if, for example, you fly out of a northern winter and land in our summer.
‘Heatwaves’ are variously defined around the world, and vary to some extent according to local conditions. In 2014 the Australian Bureau of Meteorology (BOM) provided a national definition of a heatwave:
A heatwave is now defined by three or more days of unusually high maximum and minimum temperatures in any area.
ABC weather guru Graham Creed says there are three grades of heatwave, with severe and extreme posing the most serious risk.
“Standard heatwave will only have slight effects on the general population,” he said.
“As we move into severe, that’s when we start to see on the elderly and also people with debilitating illnesses.
“Then as we move into extreme heatwave conditions, that’s when the general public and also infrastructure can be affected.”
BOM also has a national Heatwave Service, graded in three colours, with links to State health departments for further information.
Google told me that in Adelaide a heat wave is defined as five consecutive days at or above 35°C, or three consecutive days at or over 40°C. I assume that is a ‘standard’ heatwave.
In 2014 the Climate Council published a comprehensive report on heatwaves in Australia. They found that hot days had doubled during the last 50 years. As to the future, they found that for both northern and southern Australia, 1-in-20 year extreme hot days are expected to occur every two to five years by the middle of the century.
- If the current trend in greenhouse gas emissions continues through the rest of this century, today’s record-breaking hot weather will become commonplace, occurring almost every summer across the country.
The need therefore is to get emissions down, but as we saw in the most recent post on heat, emissions growth is accelerating.
The New Scientist article has an image showing the increased probability of deadly heatwaves for 1.5°C, 2°C and 4°C of warming. I don’t know exactly what that means, but the colours tell their own story about the folly of the path we are on.
The NS article also has hints on staying cool. Drinking cold water is good, and dipping hands and feet in cold water helps, as the blood can then give priority to core organs. Placing a tub of ice behind a fan gives a makeshift air conditioner. The article suggests the need for public air-conditioned refuges, but says urban planners largely ignore the heat problem.
On a personal note, I was once in charge of a public service building that was not air-conditioned, and found that humans rapidly became dysfunctional outside a range of about 18°C to 26°C. That is, with their clothes on. I also found that engineers decided the ideal temperature while walking around in a suit.
I understand that sport requiring speed and stamina should not be played when the temperature is over 26°C, if player welfare is the main concern. In the recent Brisbane International Tennis Championship we heard reports that temperatures were above 50°C on outside courts. So it was no surprise to see this, when top seed Garbine Muguruza had to concede:
- Muguruza had won a tight first set and appeared heading for a straight-sets win over Krunic when she opened up a 5-2 lead in the second.
However, she began to struggle in the 30 deg C heat and oppressive humidity as Krunic fought back to win the second set on a tie-break.
Muguruza received treatment from the physio on court before the start of the decider and broke Krunic only to collapse while serving to consolidate the service break.
In the Australian Open I believe a number of matches were decided on who had the better body-type to cope with the heat. In the men’s final between Roger Federer and Marin Čilić because the ambient temperature was above 32.5°C the roof was closed and the aircon turned on under their extreme heat policy. Commentators said that favoured Federer, but may have allowed the match to be decided on tennis skill on the night.
The women had no such luck. The temperature was under 32.5°C at the start but was over 30°C for much of the match. The standard of play, brilliant in the early part, deteriorated over the 2 hours, 50 minutes of the match. I felt perhaps Caroline Wozniacki fell over the line at the end and was not surprised to hear that the loser, Simona Halep, spent four hours in hospital being rehydrated after the match.
I have the distinct feeling that life is going to be very different in 50 years time.