Environment

As shepherds watched, it got hotter and hotter

Date
December 24, 2014

Peter Hannam
Peter Hannam
Environment Editor, The Sydney Morning Herald

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Human health – and that of other animals and even plants – is likely to become an ever more pressing public issue as temperatures rise with global warming, cities grow and populations age.

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While shepherds watched: NSW gets hotter and hotter.

While shepherds watched: NSW gets hotter and hotter. Photo: Anthony Johnson

Australia’s woodlands at risk as mercury rises

If Australia’s test cricketers suffer heat stress during the Boxing Day Test in Melbourne or January’s match at the Sydney Cricket Ground, it won’t be for want of trying.

Earlier this year, in preparation for the series against Pakistan in the United Arab Emirates, players were dispatched for intensive training in Brisbane and Darwin to examine their response to heat extremes.
Summer extremes: Surfers at Bondi Beach.

Summer extremes: Surfers at Bondi Beach. Photo: Getty Images

Aside from the standard ice baths and cool drinks – Esky-chilled beverages at 4 degrees turn out to be ideal – players swallowed capsule-sized thermometers to help team dietician Michelle Cort monitor which of them struggled most to shed heat.
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“It allowed us to keep an extra watchful eye on specific players and make sure they were doing everything they needed to do to keep the core temperature down,” Ms Cort said.

Across the summer, sports medicine will be getting a work out. In an increasingly crowded season, cricketers are vying for attention with the upcoming Asian Football Cup in addition to the regular fare of the Tour Down Under cycling, the A-League, and tennis at the Australian Open – all potentially taking place during a heatwave.

The issue of heat, though, isn’t just confined to playing fields and accompanying concrete stadiums packed with fans of the spectator variety.

The heat is on: How scientists predict Sydney’s climate will warm over the next 50 years. Graphic: Remi Bianchi, Photo: Quentin Jones

Human health – and that of other animals and even plants – is likely to become an ever more pressing public issue as temperatures rise with global warming, cities grow and populations age.

Until recently, public health authorities would issue a warning whenever the temperature was likely to exceed a certain level.

However, heatwaves are also related to the conditions people are accustomed to. To reflect that, the Bureau of Meteorology last year pioneered a heatwave service that predicts the severity of coming heatwaves based on both how far temperatures are likely to deviate from historical averages but also taking into account the previous month’s weather.

How scientists predict Sydney’s climate will warm over the next 50 years. Graphic: Remi Bianchi

In a further tweak, the bureau has added charts to assess the impact of each heatwave after it’s hit. That’s needed because people often don’t realise the damage to health can come from exposure to prolonged warmth rather than a particular temperature spike.

“If the body doesn’t have time to recover overnight, or for some period during 24 hours, that’s when significant problems start to emerge,” said Alasdair Hainsworth, assistant director of hazard prediction services at the bureau.

“We know that Australia is warming … and we believe we should provide some level of warning associated with that,” Mr Hainsworth said, adding the charts may one day be common features of weather reports.

Indeed, of the emerging signals of climate change in Australia, rising temperatures and increasing heatwaves are the probably the clearest.

For New South Wales, average maximum temperatures have already risen by half a degree over the last two decades or so. They are likely to increase by another 0.7 degrees by 2030 and as much as 2.6 degrees by 2070, according to research released by the state government and the University of NSW earlier this month.

“We know heatwaves have a big impact,” said Matthew Riley, director of climate and atmospheric science for the Office of Environment and Heritage. “They are the costliest natural disaster in terms of the loss of human life in Australia.”

While Victoria’s 2009 Black Saturday bushfires killed 174 people, at least 370 people died during the heatwave that preceded the fires – drawing much less public or media focus.

NSW Health has identified people aged over 75, infants and those taking perscription medicine that restricts perspiration as among those most at risk from heat stress.

Human physiology means that excess warmth starts to undermine health for most of us when body temperatures exceed 37.8 degrees. Similar damage is inflicted on plants when certain thresholds are crossed (see related article).

When overlaid on Australia’s famously variable climate, the existing temperature rise is also associated with heatwaves becoming more intense, more common, lasting longer, and starting earlier in spring.

Research published in August in the Journal of Climate predicts Sydney will experience as many as 42 heatwave days each summer by the end of the century, assuming greenhouse gas emissions remain at the high end of trajectories. That tally would exceed even Perth’s 40 such days and Melbourne’s 12.

“Definitely we’ll see more heatwaves and the number of heatwave days will increase,” said Sarah Perkins, a heatwave expert at UNSW’s ARC Centre of Excellence for Climate System Science and one of the report’s authors. “It’s not a good story.”

By contrast, Sydney had just three heatwave days on average 60 years ago and about six to seven now, Dr Perkins said. A heatwave is defined as having at least three days in a row with temperatures in the top 10 per cent for those days.

The government-backed study, meanwhile, generated scenarios down to 10km resolution for the first time, giving local governments greater clarity on what to expect as the climate shifts.

For now, Sydney as a whole averages fewer than 10 days of 35 degrees or warmer weather each summer. In the city’s west, residents sweat through 10 to 20 such days.

By 2030, the city can expect four more 35-plus degree days and 11 more each year by 2070, the report said.

But in the city’s west and the Hawkesbury region, the increase will be 5-10 such days by 2030 and a doubling of 10-20 more hot days by 2070.

The longer-term estimate is based on a business-as-usual emissions scenario which, if governments get serious about addressing global warming, may be too pessimistic.

On the other hand, there are reasons why the scenarios, grim as they are for heat, may be optimistic not least because they did not account for population growth.

Sydney’s population is projected to swell by 1.6 million by 2030, with most newcomers likely settle in the growth corridors in the city’s south-west and north-west .

By geography, these two areas already have furnace-like potential as demonstrated by last month’s heatwave.

Penrith set a November record maximum of 44.9 degrees – albeit in data only going back about two decades – while Richmond hit 45.3 degrees in Bureau of Meteorology records from 1939.

During a February 2011 heatwave, a Landsat satellite passed over Sydney taking infrared pictures identifying the city’s hottest spots.

Brent Jacobs, research director of the Institute of Sustainable Futures at the University of Technology, Sydney, is among those examining the heat mapping to help planners limit current and future effects of the warmth.

Dr Jacobs says developers of new housing estates usually leave little in the way of green spaces and water features that – while costly to maintain – would help counter the inevitable heat-island effects.

He is also scathing of the layout of residential roads that often loop around, ending up cul-de-sacs.

“You’re talking about an area that’s already hot,” Dr Jacobs said. “All you’re doing is creating canyons that trap in the hot air. There’s no air movement through that suburb so there’s no way for that heat to get out.”

Cricket Australia dietitian Michelle Cort, meanwhile, says people who are overweight or particularly muscular are among those who should pay special heed to warnings about heatwaves.

“The more body fat people have, the less able they are to dissipate the heat,” Ms Cort said, adding that the $100 single-use thermometer capsules will be little use for the wider public without expert monitoring.

As for the players, two provided surprising responses. NSW fast bowler Mitchell Starc proved able to dissipate heat better than his work-rate and muscle mass would imply, while Victorian all-rounder Glenn Maxwell struggled more than expected.

In the finish, the team wilted to a series thrashing to Pakistan, but managers couldn’t blame the heat.