Limiting global warming to 1.5°C would reduce risks for humans by up to 85%

Newswise – New research from the University of East Anglia (UEA) quantifies the benefits of limiting global warming to 1.5°C and identifies hotspot regions for the risk of future climate change.

The study calculates the reductions in human exposure to a range of risks – water scarcity and heat stress, vector-borne diseases, coastal and riverine flooding – that would result from limiting global warming to 1.5°C rather than only at 2°C or 3.66°C. Effects on agricultural yields and the economy are also included.

Researchers from the UK, including scientists from UEA and the University of Bristol, as well as the Dutch environmental assessment agency PBL, have found that the risks are reduced by 10 to 44% at global scale if warming is reduced to 1.5°C instead of 2°C.

Currently, insufficient climate policy has been implemented globally to limit warming to 2°C, so the team also made a comparison with the risks that would occur with higher levels of global warming. .

The risks will be greater if global warming is greater. The risks at a warming of 3.66°C are reduced by 26 to 74% if the warming is kept to just 2°C. They are reduced even further, by 32 to 85%, if warming can be limited to just 1.5°C. The ranges are wide because the percentage depends on the indicators, for example human exposure to drought or floods, that are taken into account.

The results, published today in the journal Climate change, suggest that in percentage terms the risk averted is highest for riverine flooding, drought and heat stress, but in absolute terms the risk reduction is highest for drought.

The authors also identify West Africa, India and North America as regions where risks from climate change are projected to increase the most with 1.5°C or 2°C average global warming. by 2100.

Study follows Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report, which concludes that global net zero CO2 emissions must be reached by the early 2050s to limit warming to 1.5°C with no or limited overshoot, and by the early 2070s to limit warming to 2°C.

Lead author Professor Rachel Warren, from the Tyndall Center for Climate Change Research at UEA, said: “Our findings are important because the goal of the Paris Agreement is to limit global warming to ‘well in below” 2°C and to “continue efforts” to limit to 1.5°C. This means that decision makers need to understand the benefits of aiming for the lowest number.

“Furthermore, at COP26 last year, commitments made by countries to reduce greenhouse gas emissions were not sufficient to meet the Paris targets. Currently, current policies would result in an average warming of 2.7°C, while the Nationally Determined Contributions for 2030 would limit warming to 2.1°C.

“While there are a number of additional actions planned to further reduce emissions, potentially limiting warming to 1.8°C in the most optimistic case, these have yet to be implemented and others. Further actions are needed to limit warming to 1.5°C.”

For this study, the researchers ran sophisticated computer simulations of climate change risk, using a common set of climate change scenarios in which global temperatures increase by 2°C and separately by 1.5°C and 3.66 °C. They then compared the results.

Findings include:

  • Overall, global population exposure to malaria and dengue fever is 10% lower if warming is limited to 1.5°C rather than 2°C.
  • People’s exposure to water scarcity is most evident in western India and the northern region of West Africa.
  • A continued increase in global drought risk with global warming is estimated, with hundreds of millions more people affected by drought at each successively higher level of warming.
  • By 2100, if we do not adapt, a global warming of 1.5°C would put an additional 41 to 88 million people per year at risk of coastal flooding worldwide (associated with rising sea levels 0.24 to 0.56 m), while an additional 45 to 0.56 m 95 million people per year would be threatened by a global warming of 2°C (corresponding to a rise in sea level of 0.27 at 0.64 m) in 2100.
  • The global economic impacts of climate change are 20% lower when warming is limited to 1.5°C rather than 2°C. The net damage value is reduced accordingly from US$61 trillion to US$39 trillion.

The study used 21 alternative climate models to simulate regional climate change patterns corresponding to 2°C and 1.5°C warming respectively. Previous research has used simpler models, a more limited range of climate models, or covered different risk indicators.

“Quantifying the risks avoided by limiting global warming to 1.5 or 2°C above pre-industrial levels”, Rachel Warren et al, is published in Climate change June 29.

Teresa H. Sadler