Blog 4 August 2026
Why black carbon is a major climate and health risk
Black carbon, often called soot, is a highly damaging super pollutant. It traps heat from the sun and warms the atmosphere. Alongside methane and other super pollutants, it contributes to nearly half of global warming. It also melts glaciers, disrupts regional and local weather patterns, including rainfall and monsoon patterns, and worsens risks such as extreme heat and rainfall.
As it pollutes the air we breathe, it is a major health threat and increases the risk of respiratory and heart diseases. As a component of air pollution, black carbon significantly contributes to the 8 million premature deaths a year and the trillions of dollars of economic cost (5% of global GDP) from air pollution each year. Unlike carbon dioxide, black carbon stays in the atmosphere for around one to two weeks. That means cutting emissions can deliver fast climate and health benefits for communities.
Why has policy action on black carbon lagged?
Despite its climate and health impacts, black carbon is widely underrepresented in national and global policy and processes. Four evidence and policy gaps are holding back faster action:
- Scientific uncertainty: The IPCC recognises black carbon as a contributor to global warming, but highlights scientific uncertainty around its climate impacts. For example, the IPCC’s Sixth Assessment Report estimated that black carbon contributes approximately 0.07 °C to global warming. These estimates are derived from multiple climate models that simulate the warming effects of black carbon, but these models treat key physical properties of black carbon differently, particularly its interactions with clouds, leading to a wide range of results. These uncertainties make it harder for policymakers to quantify the climate benefits of cutting black carbon.
- Uncertain emissions estimates: Global black carbon emission estimates vary widely across different inventories and regions. A comparison of measurement data with GEOS-Chem simulations found that existing emission inventories underestimated black carbon by about 38% in low- and middle-income countries, while overestimated by double in high-income countries. These discrepancies undermine accurate assessments of black carbon’s climate and health impacts and hinder the design of effective mitigation strategies and co-benefit assessments.
- Health policy gaps: Despite strong evidence of health impacts, black carbon is not explicitly regulated in global health guidelines. The World Health Organization’s updated Global Air Quality Guidelines from 2021 recognise associations between black carbon exposure and adverse health outcomes, but do not set concentration limits for the super pollutant. The absence of explicit black carbon standards weakens its prioritisation in public health policy and limits targeted action to reduce exposure.
- Climate policy gaps: International climate policy frameworks like the Kyoto Protocol and Paris Agreement primarily focus on greenhouse gases and do not address black carbon. Because black carbon is not explicitly covered under any climate frameworks, opportunities for rapid climate and air quality co-benefits remain underutilised.
How Clean Air Fund is helping close the evidence gap
Our action on black carbon programme is designed to turn scientific evidence into practical policy action. By supporting research on black carbon’s impacts, we’re building an evidence base for black carbon and resolving scientific bottlenecks. We want to give governments the evidence they need to prioritise black carbon reduction in national and global policy. The science component of the programme is especially focusing on:
- Conducting a comprehensive impact assessment of how climate models represent black carbon’s effects and strengthening regional and sectoral emissions estimates.
- Understanding how black carbon interacts with clouds and affects precipitation patterns, including by developing climate risk indicators that countries can use in assessments and planning.
- Understanding the links between black carbon and extreme heat and rainfall events, including quantifying black carbon’s impacts on health, agriculture, and the economy, and developing climate metrics for black carbon.
- Quantifying how black carbon travels from emissions sources to the cryosphere, such as the Himalayas, and how deposition on snowpacks affects glacier melting.
- Developing a tool to simulate climate response, such as temperature change and climate forcing. The tool will generate sectoral reduction pathways for the Arctic region.
- Examining the links between long-term exposure to black carbon and major chronic respiratory diseases, such as asthma and COPD, and other morbidity factors. We will also estimate the association of black carbon with these health effects and co-emitted pollutants, such as PM2.5 and NO2.
- Building consensus among the scientific community and policymakers on the climate and health impacts of black carbon.
By closing these evidence gaps, we hope black carbon gains the attention it deserves in global policymaking processes (such as IPCC, WHO, and other intergovernmental frameworks) and national policymaking. Better science will not solve the problem alone, but it can give policymakers the confidence to act faster.
Check out our Black Carbon Hub for the latest evidence, resources and news on the super pollutant, as well as the latest efforts and solutions from the climate and clean air communities.
