Global population living with extreme heat to double by 2050

Most of the impacts will be felt early on as the world passes the 1.5°C target set by the Paris Agreement, the authors warn. In 2010, 23% of the world's population lived with extreme heat, and this is set to grow to 41% over the next decades.

Published in Nature Sustainability, the findings have grave implications for humanity. The Central African Republic, Nigeria, South Sudan, Laos, and Brazil are predicted to see the most significant increases in dangerously hot temperatures, while the largest affected populations will be in India, Nigeria, Indonesia, Bangladesh, Pakistan, and the Philippines.

Countries with colder climates will see a much larger relative change in uncomfortably hot days, more than doubling in some cases.

Compared with the 2006–2016 period, when the global mean temperature increase reached 1°C over pre-industrial levels, the study finds that warming to 2 °C would lead to a doubling in Austria and Canada, 150% in the UK, Sweden, Finland, 200% in Norway, and a 230% increase in Ireland.

Our study shows most of the changes in cooling and heating demand occur before reaching the 1.5ºC threshold, which will require significant adaptation measures to be implemented early on.

Dr Jesus Lizana, Associate Professor in Engineering Science

Given that the built environment and infrastructure in these countries are predominantly designed for cold conditions, even a moderate increase in temperature is likely to have disproportionately severe impacts compared with regions that have greater resources, adaptive capacity, and embodied capital to manage heat.

Lead author, Dr Jesus Lizana, Associate Professor in Engineering Science, said: 'Our study shows most of the changes in cooling and heating demand occur before reaching the 1.5ºC threshold, which will require significant adaptation measures to be implemented early on. For example, many homes may need air conditioning to be installed in the next five years, but temperatures will continue to rise long after that if we hit 2.0 of global warming.

'To achieve the global goal of net-zero carbon emissions by 2050, we must decarbonise the building sector while developing more effective and resilient adaptation strategies.'

Dr Radhika Khosla, Associate Professor at the Smith School of Enterprise and the Environment and leader of the Oxford Martin Future of Cooling Programme, added: 'Our findings should be a wake-up call. Overshooting 1.5°C of warming will have an unprecedented impact on everything from education and health to migration and farming. Net zero sustainable development remains the only established path to reversing this trend for ever hotter days. It is imperative politicians regain the initiative towards it.'

The projected increase in extreme heat will also lead to a significant rise in energy demand for cooling systems and corresponding emissions, while demand for heating in countries like Canada and Switzerland will decrease.

Our findings should be a wake-up call. Overshooting 1.5°C of warming will have an unprecedented impact on everything from education and health to migration and farming. Net zero sustainable development remains the only established path to reversing this trend for ever hotter days. It is imperative politicians regain the initiative towards it.

Dr Radhika Khosla, Associate Professor at the Smith School of Enterprise and the Environment

The study also includes an open-source dataset of global heating and cooling demand, comprising 30 global maps at ≈60km resolution that capture climate intensity in ‘cooling degree days’ and ‘heating degree days’ worldwide. This dataset provides a strong foundation for incorporating accessible climate data into sustainability planning and development policy.

'Global gridded dataset of heating and cooling degree days under climate change scenarios' is published in Nature Sustainability. 

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