Understanding the costs and benefits of climate change mitigation and adaptation options is crucial to justify and prioritise future decarbonisation pathways to achieve net zero. Here, we quantified the co-benefits of decarbonisation for air quality and public health under scenarios that aim to limit end-of-century warming to 2ºC and 1.5ºC. We estimated the mortality burden attributable to ambient PM2.5 exposure using population attributable fractions of relative risk, incorporating projected changes in population demographics. We found that implementation of decarbonisation scenarios could produce substantial global reductions in population exposure to PM2.5 pollution and associated premature mortality, with maximum health benefits achieved in Asia around mid-century. The stringent 1.5ºC-compliant decarbonisation scenario (SSP1-1.9) could reduce the PM2.5-attributable mortality burden by 29% in 2050 relative to the middle-of-the-road scenario (SSP2-4.5), averting around 2.9M annual deaths worldwide. While all income groups were found to benefit from improved air quality through decarbonisation, the smallest health benefits are experienced by the low-income population. The disparity in PM2.5 exposure across income groups is projected to reduce by 2100, but a 30% disparity between high- and low- income groups persists even in the strongest mitigation scenario. Further, without additional and targeted air quality measures, low- and lower-middle-income populations (predominantly in Africa and Asia) will continue to experience PM2.5 exposures that are over three times the World Health Organization (WHO) Air Quality Guideline.

Ailish M Graham

and 14 more

The Australian 2019/2020 bushfires were unprecedented in both their extent and intensity, causing a catastrophic loss of habitat and human and animal life across eastern-Australia. Between October 2019 and February 2020 hundreds of fires burned, peaking in size in December and January and releasing the equivalent of half of Australia’s annual carbon dioxide (CO2) emissions. We use a high-resolution atmospheric-chemistry transport model to assess the impact of the bushfires on particulate matter with a diameter less than 2.5 µm (PM2.5) concentrations across eastern Australia. The health burden from short-term population exposure to PM2.5 is then quantified using a concentration response function. We find that between October and February an additional ~1.9 million people in eastern-Australia were exposed to ‘Poor’, ‘Very Poor’ and ‘Hazardous’ air quality index levels due to the fires. The impact of the bushfires on AQ was concentrated in the cities of Sydney, Newcastle-Maitland and Canberra-Queanbeyan during November, December and, also in Melbourne, in January. The health burden of bushfire PM2.5 across eastern-Australia, regionally and at city level is also estimated. Our estimate indicates that between October and February 171 (95% CI: 66 – 291) deaths were brought forward. The health burden was largest in New South Wales (109 (95% CI: 41 – 176) deaths brought forward), Queensland (15 (95% CI: 5 – 24)) and Victoria (35 (95% CI: 13 – 56)). At a city level the health burden was concentrated in Sydney (65 (95% CI: 24 – 105)), Melbourne (23 (95% CI: 9 – 38)) and Canberra-Queanbeyan (9 (95% CI: 4 – 14)), where large populations were exposed to high PM2.5 concentrations due to the bushfires.