A new study led by researchers from Tsinghua University Shenzhen International Graduate School (Tsinghua SIGS) was published online in Nature as an Accelerated Article Preview on September 18. Titled “Global warming amplifies wildfire health burden and reshapes inequality,” the research focuses on the growing threat of wildfires—uncontrolled fires in forests, grasslands, and shrublands that lead to major disturbances to Earth’s environment. These fires release substantial amounts of greenhouse gases and air pollutants, exacerbating climate change and endangering public health.
Amid rising global temperatures, wildfires are becoming more frequent, intense, and widespread. The particulate matter (PM2.5) in wildfire smoke is highly toxic and is significantly associated with an increased risk of premature death among exposed populations. However, significant uncertainties persist in projecting future global wildfire emissions, their health impacts, and their climatic effects, impeding effective risk management strategies.
To tackle these challenges, a team led by Associate Professor Zheng Bo from the Institute of Environment and Ecology at Tsinghua SIGS, in collaboration with Professor Zhang Qiang’s group from Tsinghua University’s Department of Earth System Science and other international researchers, developed a machine learning-based framework to predict future wildfire emissions.
Building on earlier global assessment methods, the team integrated multi-source remote sensing data, reanalysis products, and Earth system model simulations. They incorporated spatiotemporally dynamic drivers to capture multi-dimensional feedback mechanisms in wildfire ignition and spread, allowing for detailed simulation and attribution of future wildfire activity and emissions under different climate scenarios. By further combining atmospheric chemistry transport models with health impact assessment tools, the study uncovered the future health and climate effects of global wildfire emissions in a changing climate.
Figure 1. Historical changes and future projections of wildfire emissions and their impacts on PM₂.₅-related health effects and direct radiative forcing
Key Findings: Rising Wildfire Threats and Reshaped Health Inequalities
The study finds that, as climate warming and drought conditions intensify, global wildfire activity will significantly increase in the future. Under the medium emission scenario (SSP2-4.5), global wildfire carbon emissions are projected to rise by approximately 23% by the end of the century compared to current levels. Additionally, an estimated 1.4 million premature deaths per year worldwide will be attributable to PM2.5 exposure from wildfire smoke—six times the current death toll of about 230,000 (Figure 1). Under the SSP2-4.5 scenario, Africa is projected to experience an 11-fold increase in premature deaths due to wildfire PM₂.₅ exposure by the end of the century, while mid-latitude regions of the Northern Hemisphere, including Europe and North America, will see a 1–2 fold increase (Figure 2). These results underscore the severe threat posed by growing wildfire risk to global public health and its uneven regional distribution.
The study further indicates that although increased wildfire emissions will enhance the cooling effect from aerosol direct radiative forcing on a global scale, this cooling effect in the Arctic region will weaken by approximately 0.06 W/m² by the end of the century (under SSP2-4.5), potentially accelerating future polar warming (Figure 1). It is particularly noteworthy that while the cooling effect of wildfire aerosols may partially mitigate local warming trends, the greenhouse gas emissions from wildfires and the damage to forest carbon sinks will exacerbate climate warming. The multi-dimensional impacts and feedback mechanisms between wildfires and climate change highlight the complexity and urgency of wildfire management.
Amid global efforts in climate governance and clean air policies, anthropogenic greenhouse gas and air pollutant emissions are expected to decline significantly. However, climate-change-driven increases in wildfire activity are projected to become a major factor influencing future global air pollution and disease burden. Global warming not only amplifies the health risks of wildfire pollution but also reshapes its distribution across regions and economies. While less developed regions will continue to bear a substantial share of the global wildfire health burden, significantly increased wildfire activity in developed regions—coupled with aging populations—will greatly elevate their share of global wildfire health risks, altering the regional disparities in health impacts from wildfire PM2.5 exposure.
Figure 2. Health effects induced by wildfire PM₂.₅ across different regions and their global distribution patterns: a comparison between historical and future scenarios.
A Systematic and Interdisciplinary Look at Global Threat
This study represents another major achievement in the team’s ongoing research into extreme wildfire emissions and their climatic and environmental impacts, following their earlier publications: a May 2025 Nature paper titled “Air pollution modulates trends and variability of the global methane budget”, and a 2023 Science article, “Record-high CO2 emissions from boreal fires in 2021.”
"The first study focused on how wildfires release carbon dioxide and pollutants from the land surface. The second examined the physical and chemical processes of these pollutants in the atmosphere. This third study completes the picture by analyzing the ultimate downstream impact on human health," he stated.
This systematic approach allowed the team to create a comprehensive projection from fire occurrence to human health effects on a global scale, extending to the year 2100.
The interdisciplinary study combined environmental science, public health, and artificial intelligence. "The team used AI-based models trained on historical wildfire data to predict future fire frequency, intensity, and resulting PM2.5 pollution under different climate scenarios," Zheng explained. These projections were then integrated with health impact assessment models to quantify the mortality risk.
Looking ahead, the team plans to expand its scope. "Our team plans to view wildfires within the entire Earth system," said Zheng. The goal is to develop a more comprehensive assessment of their combined effects on climate, the environment, and human society, which will require deeper interdisciplinary collaboration.
Professor Zheng Bo and Professor Zhang Qiang are the corresponding authors of the paper. Dr. Zhao Junri, a former postdoctoral fellow at Tsinghua SIGS (now a designated assistant professor at Nagoya University, Japan), is the first author. Co-authors include Professor Philippe Ciais, Foreign Member of the Chinese Academy of Sciences, Distinguished Visiting Professor at Tsinghua University, and researcher at the Laboratoire des Sciences du Climat et de l'Environnement (LSCE) in France, as well as several collaborators from the University of California, Irvine, the International Institute for Applied Systems Analysis (IIASA) in Austria, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia, and graduate students from Tsinghua SIGS.
The research was supported by the National Natural Science Foundation of China, the "Carbon Neutrality and Energy System Transformation" project, and the New Cornerstone Science Foundation through the Xplorer Prize.
Full article:
https://www.nature.com/articles/s41586-025-09612-9
Related publications:
https://www.nature.com/articles/s41586-025-09004-z
https://www.science.org/doi/10.1126/science.ade0805
Written by Chen Jundou
Reviewed by Zheng Bo
