The study, published in the journal Communications Earth & Environment, suggests that even if the world adheres to the Paris Agreement to limit global warming to 2 degrees Celsius, exposure to dangerous heat “will likely increase by 50-100% across much of of the tropics”. The research, authored by researchers at Harvard University and the University of Washington, used the US National Weather Service’s heat index, which classifies “dangerous” heat as above 39C (103F) due to an increased chance of heatstroke or thermal exhaustion. The study found that without significant emissions reductions, deadly heat waves that were previously rare will become annual occurrences in the mid-latitudes – temperate regions between 30 and 60 degrees north and south of the equator. In Australia, mid-latitudes are south of a line drawn from halfway between Geraldton and Perth in Western Australia to Bourke in New South Wales, according to the Bureau of Meteorology. “The health consequences of regular very high temperatures, particularly for the elderly, the poor and outdoor workers, would be profound and require a fundamental reorientation of the dangers of extreme heat,” the researchers found. Dr Andrew King, a senior lecturer in climate science at the University of Melbourne, who was not involved in the study, said: “When you look at exceeding past high temperatures, you are more likely to do it earlier in tropical locations. than in other parts of the world.” “It’s also dangerous if you have heat combined with very humid conditions,” King said. “Our bodies sweat to cool down through evaporative cooling, and when it’s hot and humid, we can’t really do that.” “Part of the problem is that the countries most at risk in the tropics tend to be countries that are poorer … they have to adapt to a problem they didn’t actually cause.” King said precautions that could be taken to limit the health effects of high heat included better forecasting of extreme heat events, planning to ensure people were well hydrated and discouraging people from working outside on the most dangerous days. The study highlighted the need to prioritize “reducing greenhouse gas emissions and getting to net zero as quickly as possible,” he said. It comes as another paper, published in Scientific Reports, found that the 2019-20 fires led to the biggest warming of the stratosphere – the second layer of the Earth’s atmosphere – in more than 30 years. Subscribe to Guardian Australia’s Morning Mail Our Australian morning news email breaks down the key national and international stories of the day and why they matter Privacy Notice: Newsletters may contain information about charities, online advertising and content sponsored by external parties. For more information, see our Privacy Policy. We use Google reCaptcha to protect our website and Google’s Privacy Policy and Terms of Service apply. Millions of tonnes of smoke aerosols were injected high into the atmosphere by Australia’s black summer bushfires. British researchers found that smoke temporarily warmed the lower stratosphere and extended the life of the 2020 ozone hole, which develops every year during the southern hemisphere’s spring. The temperature of the stratosphere increased by 0.7 degrees Celsius from November 2019 to March 2020 – the largest increase since the eruption of Mount Pinatubo in the Philippines in 1991. “It is likely that future climate change will increase the frequency and intensity of wildfires, increasing the likelihood of more frequent stratospheric [smoke] events in the future,” the researchers found. Director of the atmospheric chemistry center at the University of Wollongong, Professor Clare Murphy, who was not involved in the research, said: “When you put aerosols into the atmosphere, they both scatter sunlight, but they can also absorb heat. The kind of aerosols you get from fires are more absorbents that look like black carbon. “Fundamentally, climate change is due to atmospheric composition… There are feedback loops in both directions with ozone depletion and with climate warming.”
