Global warming of 2°C doubles the population exposed to climate risks compared to 1.5°C rise

Multisector risk is one where the risk goes beyond tolerable in at least two of the three main sectors. At lower temperatures, hotspots occur primarily in south and east Asia, but with higher global temperatures, hotspots further spread to Central America, west and east Africa, the Middle East and the Mediterranean. The actual global land mass affected is relatively small, at 3-16 percent depending on the scenario. However, the areas at highest risk tend to be densely populated. At 1.5°C of warming, 16 percent of the population of the world in 2050, 1.5 billion people, will have moderate-to-high levels of multisector risk. At 2°C of warming, this almost doubles to 29 percent of the global population, 2.7 billion people. At 3°C of warming, that figure almost doubles again, to 50 percent of the population, or 4.6 billion people.

Depending on the scenario, 91-98 percent of the exposed and vulnerable population live in Asia and Africa. Around half of these live in south Asia alone, but Africa is likely to face greater risks as the least developed region with high social inequality.

With the world already around 1.0°C warmer than pre-industrial averages, in 2015 global leaders agreed in Paris to limit average warming by 2°C, with the ambition of limiting warming to 1.5°C if possible. The large differences, the researchers note, even between warming of 1.5°C compared to 2°C, are striking, and underline the multidimensional risks of climate change and the need to keep warming as low as possible.

Targeting socioeconomic development in hotspot areas is particularly important for reducing vulnerability in places where impacts will be most severe. Sustainable development in hotspot areas could reduce the number of people who are exposed and vulnerable by an order of magnitude, from 1.5 billion to 100 million, compared to the high inequality scenario. The poorest in society will likely be disproportionately impacted by climate change, and greater efforts to reduce inequality and promote adaptation are urgently needed.

“The research will be most relevant to policymakers and others looking to understand the benefits of keeping the average global temperature rise to 1.5°C rather than 2°C, as well as providing insights into the regions most at risk across different sectors. The poorest and most vulnerable countries are most at risk and this work will aid to identify integrated, cross-sectoral approaches and target resources for maximum impact,” says Astrid Hillers, senior environmental specialist at GEF.

Keywan Riahi, IIASA Energy program director, adds: “The research indicates locations where meeting the Sustainable Development Goals (SDGs) is not only important but also very challenging, and shows the substantial importance of targeted poverty reduction that is required in some regions to reduce vulnerability.”

— Read more in E. Byers et al., “Global exposure and vulnerability to multi-sector development and climate change hotspots,” Environmental Research Letters (in press) (DOI:10.1088/1748-9326/aabf45