Today, I and many other scientists know that reducing black carbon is a must. Indeed, the latest IPCC reports attribute 0.1°C of warming to black carbon and recommend steep cuts of the pollutant by 2030 to meet the Paris Agreement goals.
Yet, in the vast arsenal of climate actions, where every solution is touted as a silver bullet to address climate change, reducing black carbon remains all too often overlooked, even by experts. But that must change – and quickly – if we are to stop climate change and safeguard a healthy, sustainable future for all.
So, what is black carbon?
Black carbon is particulate matter that results from the incomplete combustion of fossil fuels and biomass in household cooking, transportation, industrial processes, and residential heating. The most significant sources of black carbon are household cooking and transportation, which contribute to more than 70% of total anthropogenic emissions. Wildfires are also an important – and rapidly growing – source of black carbon.
It’s important to note that black carbon is not a greenhouse gas like methane and carbon dioxide. Black carbon is a solid particulate matter, and as such it directly impacts warming by absorbing sunlight and indirectly by reducing the albedo (reflectivity) of surfaces such as ice and snow.
Though scientists have known about the detrimental effects of black carbon for a long time, it has yet to receive the attention it warrants. This unfair treatment of black carbon started in the late 1990s with the Kyoto Protocol – the first global agreement to lower greenhouse gasses and mitigate climate change through international cooperation – which excluded black carbon from its list of climate pollutants.
Since black carbon occupies an ambiguous space as both a climate and air pollutant, it has been sidelined from efforts to reduce either, with stakeholders from each group passing responsibility to the other. But while politicians and world leaders waffle, black carbon continues to devastate our planet and its people.
A threat beyond warming
Black carbon’s ability to warm the planet is several hundred times greater than carbon dioxide in the near term, making it the most potent short-timescale climate pollutant.
The good news is that black carbon stays in the atmosphere for just a few days to weeks. This means that reducing black carbon can immediately reduce warming and slow the rapid temperature increases many places around the world have been experiencing as of late. Changes in atmospheric black carbon in North America between June 3-8, 2023 following the large-scale Canadian wildfires.
Since black carbon is a particle, however, when it settles on snow and glaciers it accelerates melting by decreasing the snow’s reflectivity, especially in the Arctic and Himalayas.
In the Arctic – which is already warming four times faster than the global average – black carbon deposits act as a catalyst, accelerating the fragile ecosystem toward irreversible tipping points. Most of the black carbon settling in the Arctic comes from wildfires and ship emissions. Shipping-related black carbon emissions in the Arctic doubled between 2015 and 2021. Worse still, with more emissions comes more melting, opening up new shipping routes that lead to more pollution, creating a destructive feedback loop.
In South Asia, black carbon from brick kilns, vehicles, and unclean cooking fuels that settles on the adjoining Himalayan Range leads to faster glacier melt. This results in devastating floods and streamflow changes that negatively impact the socio-economic well-being of more than a billion people in the Indo-Ganges Basin.
Beyond the glaciated reaches of our planet, black carbon has been shown to impact the South Asian monsoon and rainfall patterns in West Africa by altering atmospheric processes. This can lead to complex and varied regional impacts. For instance, black carbon can cause flooding in northern China, while in Southern China it can induce drought.
However, the impact of black carbon doesn’t stop with global warming, melting glaciers, and changing rainfall.
As an air pollutant, black carbon contributes significantly to global deaths from cardiovascular disease. It is far deadlier than other particulate matter. In households that use wood, coal, or other unclean cooking fuels – the largest source of black carbon – indoor air pollution can be as much as 100 times higher than the World Health Organization’s recommended levels. Studies from China, India, and the US all show that black carbon is directly responsible for thousands of deaths every year.
These adverse health and climate impacts translate into large economic losses. In China, it is estimated that the economic toll from short-term exposure to black carbon in 2017 was more than US$7.5 billion. The impact of long-term exposure was even starker, resulting in financial losses of over US$53 billion.
Although these impacts are felt around the world, the socio-economic (health, water security, economic opportunity) effects are felt most acutely at the local or regional level. Therefore, even world leaders who forget that instability anywhere is a threat to stability everywhere should feel compelled to act out of local self-interest.
A win-win-win for people and the planet
Reducing black carbon is a triple win, promising immense climate, health, and socio-economic benefits.
For the climate, it will lead to a short-term reduction in global warming, the protection of Arctic and Himalayan glaciers, and the stabilization of rainfall patterns.
For human health, it will save millions of lives. In my home country of India alone, reducing black carbon could save more than 400,000 lives each year by improving air quality. In Sub-Saharan Africa, reductions could avoid nearly half a million premature deaths annually.
Finally, for local socio-economic systems, it will have ancillary benefits such as increasing gender equality, reducing deforestation, and providing jobs and income opportunities. For example, women in low- and middle-income countries often spend many hours each week collecting wood for cooking. Access to clean fuel would dramatically reduce time spent collecting and cooking, and that time could then be used for recreational or economic activities. The World Bank found that the dependence on unclean cooking fuels leads to worldwide losses in women’s productivity of US$800 billion annually. In East Africa, where the demand for woodfuel contributes to rapid deforestation, clean cooking protects forests and the biodiversity they harbor.
A readily solvable problem
Given the myriad detrimental impacts of black carbon, you would think curtailing its emissions would be at the forefront of governmental agendas worldwide. Yet, disappointingly, efforts to reduce black carbon are severely lacking.
Only 12 countries set reduction targets for black carbon during the first round of Nationally Determined Contributions (NDCs), each country's self-defined climate action plans under the Paris Agreement.
While advanced economies like the US, China, and the European Union have made commendable progress in reducing black carbon pollution, this headway is threatened by increasingly severe wildfires and, globally, is eclipsed by the rising emissions in low- and middle-income countries (LMICs).
Based on existing policies, black carbon is set to skyrocket. For instance, transportation-related black carbon emissions in Africa could double between now and 2040.
Fortunately, addressing black carbon in LMICs doesn’t need a technological revolution. We have existing solutions that can be implemented between now and 2030 to reduce anthropogenic black carbon emissions drastically.
These solutions include phasing out unclean cooking fuels, adhering to the most up-to-date diesel vehicle standards, finding alternatives to agriculture burning, and eliminating traditional brick kiln technologies and heavy fuel oil from the shipping industry.
To succeed, these solutions must be coupled with the creation and implementation of robust policies and regulations that encourage their adoption. This approach should include strategic interventions in the areas most afflicted by black carbon, targeting them as hotspots for immediate action. Equally vital is fostering dynamic collaborations among philanthropists, multinational development banks, businesses, and non-governmental organizations to accelerate the widespread deployment of these critical solutions.
Recently, in the quest to reduce shipping emissions in the Arctic, we’ve seen what can be accomplished when these stakeholders come together. After years of effort, a heavy fuel oil ban in the Arctic will finally come into effect on July 1, 2024. While this ban has loopholes – for instance, a ship that flies a flag of a country sharing the border with the Arctic can still use heavy fuel oil until July 1, 2029 – this is a major win for mitigating some of the worst impacts of black carbon. Similar interventions and policy frameworks that acknowledge the outsized threat of black carbon must quickly be adopted across other regions and sectors.
Five steps for reducing black carbon emissions
First, policymakers need a targeted approach to address emissions hotspots. About 20% of global black carbon emissions emanate from eastern China, northern India, and Nigeria. Addressing industrial and residential emissions in these regions can rapidly reduce black carbon emissions over the next decade.
Black carbon hotspots are shown in red and purple. About 20% of global black carbon emissions emanate from eastern China (A), northern India (B), and Nigeria (C). The light blue lines in the ocean are black carbon associated with global shipping.
Second, countries must treat black carbon as the urgent threat that it is by including it in their climate action plans which are due next year. As countries submit their updated NDCs – many of whom will do so this year at COP29 – they should introduce targets for black carbon.
Third, philanthropists, development banks, and carbon project developers must stop evaluating projects from a ‘carbon only’ lens and look at the ancillary human well-being benefits they generate. Such a framework would prioritize projects like clean cooking, decentralized solar, and improved brick kilns which have many human and environmental benefits.
Fourth, development banks, philanthropists, and investors must work together. Black carbon solutions such as clean transportation or clean cooking in LMICs are inherently risky due to currency fluctuations, high upfront costs, and higher chances of default. Collaboration between the different stakeholders could foster new financial mechanisms that reduce the lenders’ risks and the burden on borrowers. For example, in the initial phase of a project, funders can work together to share and distribute risks, opening the door for risk-averse investors. Initiatives like the Spark+ Africa Investment Fund have used innovative financial models that provide viable pathways for multilateral development banks, bilateral development agencies, and foundations to work in concert on climate solutions.
Finally, businesses need to realize that solutions that reduce black carbon emissions represent a unique opportunity to generate profit while improving the well-being of communities in LMICs. This is especially relevant for clean cooking, improved brick kilns, and alternatives to crop burning. Providing viable solutions should not be seen as charity but as a business opportunity that benefits people and the planet. Clean cooking products such as KOKO Fuel and alternatives to burning crops such as effective microorganism soil additions are a testament to how the market can support black carbon emission reductions.
Urgent action is the only way forward
While there is no silver bullet to the monumental challenge of climate change, some solutions punch well above their weight, and reducing black carbon is one of them. Low-tech, readily available solutions to reduce black carbon can save millions of lives annually while swiftly decelerating global warming. We can no longer overlook this critical issue; the time for action is now.
This article is also published on Project Drawdown. illuminem Voices is a democratic space presenting the thoughts and opinions of leading Sustainability & Energy writers, their opinions do not necessarily represent those of illuminem.
