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Heat wave mortality studies reveal climate change impacts and risk for cities

Mortality rates during heat waves have been put in the spotlight with research from The University of Queensland showing a 20% increase in heat wave-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 heat waves than in regional areas.

The two studies examined the mortality burden of heat waves 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 heat waves with associated periods of higher mortality will occur more often than they did in the past," Dr. Osborne said.

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

Heat wave 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 heat waves, through a Heat wave Vulnerability Index.

Ph.D. 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 Heat wave Vulnerability Index, frequently used in other countries, could reliably predict heat wave 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 heat wave related deaths.

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

'Heat island effect'

The researchers found that even during low-intensity heat waves there was a strong association with deaths and the Heat wave 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 Heat wave Vulnerability Index could be used to predict an increase in ambulance callouts and mortality rates during heat waves, 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 heat waves, but we believe a vulnerability index could help supplement this to help communities plan and build resilience."

Mr. Amoatey said a heat wave was considered a period of 3 consecutive days where the maximum temperature was in the top 5% for that area.

Climate change impacts on heat wave deaths

In a separate study, researchers from UQ and The Australian National University analyzed mortality rates during an extreme heat wave 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 heat wave-related mortality in the 2009 event by 20%," 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 heat waves."

The Heat wave Vulnerability Index research is in Environmental Impact Assessment Review.

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