A new University of Waikato-led study, published this week in Climatic Change, has provided a comprehensive assessment of the risks associated with extreme heat in Aotearoa for the first time.
Led by Dr Luke Harrington, a Senior Lecturer in Climate Change at Te Aka Mātuatua School of Science, the analysis offers a new framework to identify local heatwaves for individual locations around the country.
Researchers used a framework of relative rarity to identify what temperatures need to be reached before local heatwaves occur across the motu, as well as identifying regional differences in the persistence of extreme hot spells and how the benefits of overnight cooling can also vary during local heatwaves.
Dr Harrington says results show the hottest days of the year have warmed by more than 0.5 °C over the last 20 years for many populated regions, a rate which exceeds average annual changes across the country.
“When evaluating the risks associated with unusually extreme hot events in Aotearoa, complex regional differences emerge. While the East Coast of both islands witness higher absolute temperatures during local heatwaves, lower levels of day-to-day temperature variability in the northern half of the North Island will translate to larger risks with further warming over the twenty-first century.”
Dr Harrington says on average, the frequency of local hot days has increased by 50% when comparing the last ten years with a relatively recent baseline period of 1981-2000.
“This data helps to identify which regions in New Zealand are more (or less) susceptible to the adverse impacts of extreme heat, how the characteristics of extreme heat can vary for different parts of the country, and how further changes might emerge in the future.
“Combined, this information will give local councils, health providers, and central government a common evidence base, a crucial step in ensuring local communities can successfully adapt to the heatwaves of tomorrow.”