Decade of Tracking Reveals Sharp Rise in Heatwave Days for Infants and Seniors Across Oceania

A comprehensive assessment tracking health and environmental indicators across Australia and Aotearoa New Zealand reveals that infants and older adults faced unprecedented increases in heatwave exposure over the past decade, driven heavily by human-caused climate change. The multi-institution study examines 28 distinct indicators spanning health hazards, adaptation planning, economic costs, mitigation efforts, and public engagement, providing a stark look at how shifting weather patterns intersect with human wellbeing.

The collaborative evaluation was published in The Medical Journal of Australia as part of the ongoing Oceania Regional Centre reporting framework. Researchers analyzed climate data showing that global atmospheric carbon dioxide reached 425.65 parts per million in 2025, contributing to the warmest 11-year period on record globally between 2015 and 2025.

How Much Have Heatwave Days Increased for Vulnerable Populations?

The analysis shows that between 2016 and 2025, infants experienced an average of 4.6 heatwave days per year in Australia and 7.4 in New Zealand. These figures represent dramatic increases of 66 percent and 109 percent, respectively, compared with baseline periods, with adults aged 65 and older facing comparable escalations. Researchers utilized ERA5 temperature data alongside population mapping to determine that human-caused climate change was responsible for 65 percent of heatwave days in Australia and 73 percent in New Zealand between 2021 and 2025.

Extreme ambient temperatures are also reshaping daily habits, particularly outdoor physical activity. In 2025, individuals in Australia encountered an average of 480 hours of moderate heat stress risk during outdoor activities such as brisk walking, marking a 47.5 percent rise from baseline measurements. Furthermore, extreme heat stress conditions that necessitate stopping outdoor exertion altogether totaled 16 hours, surging by 90.1 percent.

What Are the Psychological Tolls and Economic Burdens on Communities?

Beyond physical health hazards, the study highlights growing mental health pressures, particularly among young people. Data drawn from youth surveys involving 16,230 participants aged 14 to 19 years old revealed that 49 percent worried that climate change threatens people and the planet, while 55 percent felt sadness over species extinction and suffering animals. Crucially, 13.5 percent of surveyed youth reported that these emotional responses negatively interfered with daily activities like sleeping, concentrating, or going to school.

Economically, the financial damages tied to climate-related mortality are escalating rapidly. Among adults aged 65 and older, heat-related deaths translated into years of life lost that averaged 1.49 billion United States dollars annually in Australia between 2021 and 2025. This figure represents a 119 percent increase compared to the beginning of the century. In New Zealand, equivalent heat-related mortality costs climbed by 342 percent to reach an average of 229 million United States dollars per year over the same recent window.

Where Is Progress Being Made in Mitigation and Adaptation?

Despite mounting risks, the health and energy sectors show pockets of proactive transition. Renewable energy generation in Australia continued an upward trajectory, with rooftop solar installations surpassing 4 million units and renewables accounting for 40 percent of electricity generation in 2024. Active transport options also expanded, with computer vision analysis tracking significant increases in pedestrian and cycling detection in metropolitan areas like Melbourne and Sydney between 2022 and 2025.

On the policy front, adaptation frameworks have advanced, highlighted by New Zealand’s Health National Adaptation Plan and Australia’s expanding climate risk assessments. Both nations achieved advanced ratings in the provision of climate services to the health sector according to World Meteorological Organization metrics. However, researchers caution that net fossil fuel subsidies, emissions-intensive agricultural sectors, and declining national media coverage present ongoing hurdles that threaten to undermine future resilience.

The research was published in The Medical journal of Australia on November 1, 2026.