Human-induced climate change drives rising heatwave deaths in cities

Mortality rates during heatwaves have been put in the spotlight with research from The University of Queensland showing a 20 per cent increase in heatwave-related deaths due to human-induced climate change.

Another UQ study has also revealed people living in cities are at a higher risk of dying from heatwaves than regional areas.

The two studies examined the mortality burden of heatwaves in Australia and Associate Professor Nicholas Osborne from the School of Public Health hopes this research will assist communities and health authorities to prepare for extreme temperature events.

Our results suggest heatwaves with associated periods of higher mortality will occur more often than they did in the past.

These higher mortality rates associated with extreme temperature heatwaves are projected to continue and we hope our research will help communities be better prepared for heatwaves."

Dr. Nicholas Osborne, Associate Professor, School of Public Health, The University of Queensland

Heatwave risk for those living in cities

In one study, UQ researchers analyzed two decades worth of temperature and mortality data to determine which areas in Australia are more vulnerable to heatwaves, through a Heatwave Vulnerability Index.

PhD candidate Patrick Amoatey, from the School of Public Health, said the study – the largest of its kind conducted in Australia – found people living in cities were at higher risk of death during extreme temperature events.

 "We used an index mapping tool to assess how human populations will fare under a range of heat scenarios," Mr. Amoatey said.

"We found the Heatwave Vulnerability Index, frequently used in other countries, could reliably predict heatwave related deaths in Australia.

"In analyzing data for more than 2000 suburbs, we found city dwellers with low income, low education, diabetes and limited access to health services, were at the highest risk of heatwave related deaths.

"This was the case for all of Australia's capital cities, which are home to 70 per cent of Australia's population."

'Heat island effect'

The researchers found that even during low-intensity heatwaves there was a strong association with deaths and the Heatwave Vulnerability Index in Australia's capital cities.

"We believe the risk is higher in cities because of the 'heat island effect', as there are more heat-absorbing surfaces like roads, buildings, and railway lines," Mr Amoatey said.

"In Greater London, for example, research has shown the Heatwave Vulnerability Index could be used to predict an increase in ambulance callouts and mortality rates during heatwaves, which is helpful for health authorities and something we could use in Australia.

"We already have useful tools and State-based action plans to reduce the impact of heatwaves, but we believe a vulnerability index could help supplement this to help communities plan and build resilience."

Mr Amoatey said a heatwave was considered a period of 3 consecutive days where the maximum temperature was in the top 5 per cent for that area.

Climate change impacts on heatwave deaths

In a separate study, researchers from UQ and The Australian National University analysed mortality rates during an extreme heatwave in Victoria in January 2009, along with decades of climate data, to examine the impacts of climate change on heat related deaths.

An estimated 374 excess deaths occurred in Victoria during the five-day event, with maximum temperatures reaching 12 – 15 degrees above normal.

"Human-induced climate change had increased the excess heatwave-related mortality in the 2009 event by 20 per cent," Dr Osborne said.

"These findings were in line with other research that shows heat-related deaths are increasing due to human-induced climate change.

"From a public health perspective, our studies and further research can provide guidance on the need for adequate health infrastructure and workforce that might be needed to cope with higher demand for health services during heatwaves."

The Heatwave Vulnerability Index research is published in Environmental Impact Assessment Review.

The mortality and climate change research was led by ANU's Professor Sarah Perkins-Kirkpatrick and is published in Environmental Research Climate.