The degree to which policies succeed in curbing the rise in global temperature to below 2.0 °C could have a profound effect on our exposure to heatwaves. As many as 420 million fewer people would see frequent extreme heat waves if the rise can be limited to 1.5 °C, based on recent simulations.

Both 1.5 °C and 2.0 °C scenarios indicate hot spells ahead. For example, in a 1.5 °C world, 13.8% of the world population will be exposed to severe heat waves at least once every 5 years. But this fraction becomes nearly three times larger (36.9%) under 2 °C warming, which – as the researchers point out – corresponds to a difference of around 1.7 billion people.

A very high-resolution global model designed to resolve local details and small-scale processes provides the foundation for the analysis. The work was performed by a team based at the European Commission’s Joint Research Centre, ETH Zürich, Switzerland, and the Swedish Meteorological and Hydrological Institute.

Resolving atmospheric conditions at high-resolution pushes up the amount of time needed to generate results; the group notes that its study is based on a relatively limited number of model simulations. However, the team believes that over the regions most affected by a future increase in intensity and frequency of extreme heat waves – Africa, South America, and South-East Asia – its results are statistically significant and robust.

Regional maximum temperature on land is expected to increase more than mean global temperature. Together with greater temperature variability, this could result in more intense and longer heat waves. But heat waves are not the only impact of rising global temperature. To be better prepared, institutions need to consider a wide range of events.

“We are working to assess, in an integrated and consistent way, the risks of multiple climate hazards that also include floods, droughts, forest fires, coastal surges and sea level rise to evaluate different adaption options,” says Alessandro Dosio of the EC Joint Research Centre. “The aim is to quantify the risk of these hazards in current and future time-frames taking into account different climate change scenarios to understand the possible impact on people and critical infrastructures.”

High-resolution models such as the simulations used in the current study could help identify regions where adaptation options may be needed in more detail.

Dosio and colleagues presented their work in Environmental Research Letters (ERL).