Increasing global warming from currently one to two degrees Celsius by mid-century might put about 25 per cent more people at risk of tropical cyclones, a new study has found out.

However, emission reductions that would limit global warming to 1.5 degree Celsius could cumulatively protect over 1.8 billion people from exposure to tropical cyclones until the end of this century, it said.

Already today, hurricanes and typhoons are among the most destructive natural disasters worldwide and potentially threaten about 150 million people each year. Adding to climate change, population growth further drives tropical cyclone exposure, especially in coastal areas of East African countries and the US.

"If we add population growth to two degrees Celsius global warming, in 2050 we could even see an increase of approximately 40 per cent more people exposed to cyclones," said researcher at the Potsdam Institute for Climate Impact Research (PIK) and the Deutscher Wetterdienst (DWD), Tobias Geiger.

"As the global population is projected to peak around mid-century, more people will face more intense cyclones, due to climate change -- putting that higher population at greater risk," Geiger, who also is the lead author of the new study published in 'Nature Climate Change' said in a release.

The global ambition is to limit warming to well below two degrees Celsius yet compared to unmitigated climate change even reaching two degrees Celsius of global warming 50 years later could lead to a quite different outcome, as an interdisciplinary team of scientists from Germany, Switzerland and the US found in a computer-based analysis: Until 2100, population models project an unforced, regular declining population in cyclone prone areas on a global scale.

"This would partially compensate for the additional exposure caused by warming as Geiger underlined: "If we rapidly reduce greenhouse gas emissions and reach two degrees Celsius of global warming only in 2100, this is likely to limit the increase of people in danger of cyclones to 20 per cent. This finding is key as it shows that reducing global warming potentially postpones severe tropical cyclone impacts to the late second half of the century, when there would be far fewer people at risk."

Timing is key when assessing exposure to cyclones

In the study, the scientists analysed the joint impacts of demographic development and climate change on people exposed to tropical cyclones -- and found that timing of when certain warming levels are reached becomes crucial. The results are even more obvious on the country level, explained Johannes Gutschow.

"Our model shows, with unprecedented detail, that in 2050 all countries at high risk of tropical cyclones are projected to see a rise in exposure. Due to the projected population growth, we found exposure changes of nearly 300 per cent in some East African countries, up to 100 per cent in the US and also a strong increase for the Arabian Peninsula."

This picture changes under less rapid warming scenarios. Johannes Gutschow added: "Basically, our computer model can calculate the impact of any given warming scenario, on a global and country scale, and its implications for the number of people at risk by tropical cyclones. Our findings most likely also hold true for a variety of other climate extremes, whose occurrence only depends on absolute warming and not on the timing."

Co-lead of PIK's Research Department on Transformation Pathways, Katja Frieler, underlined: "In line with the NDCs, the number of people at risk of cyclones would keep rising throughout the century, for instance in the hurricane-prone regions of the US."

"Emission reductions that would limit global warming to 1.5 degree Celsius could cumulatively protect over 1.8 billion people from exposure to tropical cyclones until the end of this century compared to the warming under currently proposed emission reductions. It is thus high time to rapidly reduce greenhouse gas emissions to keep as many people safe as possible," the release added.