Surge in Heatwave Deaths Linked to Climate Change Seen

Two studies by the University of Queensland (UQ) show that heatwave-related deaths in Australia have risen by 20%. Compared to those in regional locations, individuals living in urban areas are more likely to succumb to extreme heat.

The first study, a collaboration between UQ and The Australian National University (ANU), is titled “Attributing heatwave-related mortality to climate change: a case study of the 2009 Victorian heatwave in Australia.” It analysed the number of fatalities during a severe heatwave in Victoria in 2009, which remains the deadliest heatwave in the country’s history.

Longer and more intense heat waves

In the summer of 2009, southeastern Australia experienced one of its most prolonged and intense heatwaves, lasting from January 27 to February 8. During this period, temperatures soared above 44°C on two occasions: from January 28 to 31 and February 6 to 8.

During the heatwave, daily maximum temperatures in the affected region were 12°C to 15°C higher than normal between January 28 and 31. While conditions improved slightly on February 1, the most intense heat in Victoria hit on February 7 when nearly the entire state saw record-breaking temperatures, with Melbourne reaching 46.4°C, its hottest-ever temperature in 150 years of records.

The 2009 heatwave had severe and widespread impacts. In Victoria, ambulance callouts increased by up to 45%, while deaths on arrival rose by 70%. The state’s Chief Health Officer reported 374 excess deaths, representing a 62% increase compared to the typical number expected for that time of year.

Impact of climate change

The study investigated the impact of climate change on mortality rates during a heatwave in Australia. Research connecting climate change to human fatalities is still relatively new, with most studies conducted in the northern hemisphere. However, this study is the first to focus specifically on Australia in the southern hemisphere.

Researchers used a model to analyse the relationship between high temperatures and death rates during heat waves. Using data from eight climate models, they compared simulations of the 2009 heat wave with and without considering human-driven climate change. They found strong evidence that climate change has likely made heat waves like the one in Victoria in 2009 more frequent and intense.

The results showed that events similar to the 2009 heatwave happen twice as often due to human-caused climate change. It also estimates that around six to seven additional people died (about a 20% increase) during the heatwave because of the climate’s warming influence. This conclusion aligns with other research showing that climate change has increased the health impacts of temperature extremes worldwide.

The second study, “Evaluating the association between heatwave vulnerability index and related deaths in Australia,” focused on identifying vulnerable populations using the Heatwave Vulnerability Index. It analysed data on temperature and death over twenty years in over 2,000 Australian suburbs.

Their findings show that city dwellers are more likely to die from heat waves compared to those living in regional areas. Particularly vulnerable city residents belong to the low-income, low-education groups, those with poor access to health care and those with medical conditions like diabetes.

The urban heat island (UHI) effect also intensifies heat waves, making them more fatal. Urban environments are characterised by impervious structures and surfaces such as cement, asphalt, steel, and glass, which absorb and retain heat and raise air temperatures in the area.

Adapting to heat for the future

Climate change is raising temperatures and making more heat waves common and intense. Both study findings underscore the importance of preparedness from public health sectors, improving the health infrastructure, increasing access to cooling centres, and incorporating vulnerability assessments into planning to lower the risks and associated deaths caused by heat waves and intense heat in cities.