The Low Hanging Climate Pollutant

In the zero-sum climate change debate, there’s not much political space to discuss stopgap measures that would go a long way towards addressing climate change now. Take the issue of black carbon (also known as black soot), a noxious pollutant in developing countries that emanates from inefficient cooking stoves. Here’s a revelatory passage from a 2009 NYT story by Elisabeth Rosenthal:

While carbon dioxide may be the No. 1 contributor to rising global temperatures, scientists say, black carbon has emerged as an important No. 2, with recent studies estimating that it is responsible for 18 percent of the planet’s warming, compared with 40 percent for carbon dioxide. Decreasing black carbon emissions would be a relatively cheap way to significantly rein in global warming “” especially in the short term, climate experts say. Replacing primitive cooking stoves with modern versions that emit far less soot could provide a much-needed stopgap, while nations struggle with the more difficult task of enacting programs and developing technologies to curb carbon dioxide emissions from fossil fuels.

In the Hartwell Paper, which I first discussed earlier this week, the authors suggest prioritizing action on “non-CO2 forcing agents,” such as black carbon. The paper argues that addressing this significant (though under-discussed) pollutant can 1) help build necessary political traction for climate policy, 2) vastly improve public health and 3) substantially reduce greenhouse gases in the short-term.

Oddly, though, the paper doesn’t offer any policy recommendations for eradication of black carbon emissions.  So via email, I asked Hartwell co-author Atte Korhola, a professor of environmental change at the University of Helsinki, to elaborate on why we should take black carbon seriously in the climate debate, and to offer some concrete actions that can help reduce the harmful soot.

Atte Korhola: Black carbon is a ubiquitous product of incomplete combustion, formed by natural forest fires, motor vehicles, coal plants and myriad other sources. According to current estimates diesel combustion and residential fuel use (from coal, wood and agricultural debris) each produce roughly one quarter of the total emissions of soot; another 40% comes from wildfires and controlled agricultural burning; various industrial sources make up the remainder.

Soot contains both black carbon and light-colored particles that cool the planet. Smoke produced by sources such as cooking stoves and diesel engines tends to be rich in darker particles, so the pollution control focus should be on sources dominated by black carbon, such as residential combustion of solid fuels and high-emitting diesel engines, that have a stronger warming effect than others such as biomass burning, which is generally dominated by organic carbon.

Reducing black-carbon emissions isn’t really a technical problem “” modern stoves and filters can do most of the work “” so much as an issue of governance and resources. New combustion techniques and after-treatments often reduce particle emissions by several orders of magnitude in provision of the same service. Simply replacing solid fuels in home cooking stoves in developing countries with cleaner fuels and combustion technologies can lead to dramatic improvements in health and is eminently feasible. Actions may be fundable as part of general aid programs or under the UN Framework Convention on Climate  Change (UNFCCC) Clean Development Mechanism (CDM).

Much of the focus should be on developing countries. Governments should already be working to clean up diesel emissions and to improve cooking stoves especially in southeast Asia, where the health problems are most acute. But also industrialized nations could clean up fossil fuels further and reduce agricultural emissions at home. Emissions in the developed parts of the world are dominated by transportation sources such as heavy duty diesel trucks.

Addressing BC emissions from public transport is likely to be a promising way to reduce climate interference. For example, some studies have reported that the fuel switching policy (e.g. to natural  gas) resulted in a dramatic reduction in BC emissions from buses, e.g. in India.

According to conservative estimates, one ton of black carbon causes about 600 times the warming of one ton of carbon dioxide over a period of 100 years. Unlike carbon dioxide, which stays in the atmosphere for centuries, black-carbon particles remain in the air for just a matter of weeks. So, in principle, efforts to eliminate emissions could quickly reduce the warming power of this pollutant.


In April of 2009, a week after Rosenthal’s NYT article on black carbon was published, there seemed to be some bi-partisan agreement on tackling the problem. More recently, though, the issue in the U.S. debate has become inextricably bundled with pending (and virtually paralyzed) congressional climate legislation. On this note, it bears mentioning that the Hartwell paper suggests we

need to separate the policy frameworks and interventions for attending to shortlived versus long-lived climate forcing agents.

9 Responses to “The Low Hanging Climate Pollutant”

  1. Hank Roberts says:

    > black carbon … improve cooking stoves
    But Google the idea first and look for collateral damage. Remember how we outsiders helped all those folks in India and Pakistan who were drinking surface water, by providing wells?  Oops ….
    Don’t overlook, just for example, information like this:
    “… In wet seasons, according to many households, the kitchen smoke is essential to prevent moulds and fungi attacking many foods. Therefore it is not unusual to observe the practice of leaving a smouldering fire in the stove after cooking, even though the user admits that the smoke often causes eye irritation.

    In a large part of rural Asia, malaria is still a real threat. It is dangerous to allow a free penetration of mosquitoes and other poisonous insects in to the house during the evening and night hours. Many of the poor households do not have mosquito nets to sleep in. Therefore smoke, in addition to providing some warmth, provides some protection to health by repelling insects. Mosquito repellents in sticks/coils, ointments or sprays are not only expensive and rarely available in the village, but are not as effective as smoke.

    Livestock also need protection against flies and harmful insects, particularly when kept in the shed/stall day and night. In Nepal, for example, animals’ stalls are often located near the household cookstove on the ground floor. I once witnessed a lady using a special chimney pipe she had improvised to take smoke to protect livestock and household members from insects.

    Preservation of building material through the indirect deposition of tar from cooking smoke, in particular for the thatched roof and wooden upper structures, is also highly valued by rural households. The use of wood preservatives is still rarely practiced.

    Heat for domestic comfort and health in high altitude areas of Asia is still dependent, in a large part, on cookstoves. Removal of smoke from the fireplace/kitchen often compromises this benefit of the open fire. In Bhutan, Nepal, northern parts of India, Pakistan, China, Vietnam, Myanmar etc., the space heating role of stoves deserves high attention when smoke reductions or removal are to be achieved.

    So what should be the common stand for improved stove programmes on the smoke issue? Is it sufficient to emphasize household smoke problems alone? Can this ‘problem’ be solved by stoves alone or as part of broader social development programmes? Should an integrated approach be taken simultaneously so that the demand for smoke in the households diminishes or vanishes? This means better sanitation and health care, better rural housing (modest, comfortable, safe and decent), improved rural kitchen design for better ventilation, lighting, cleanliness, work function and cooking efficiency’ improved household food security, etc.

    If improved stoves are to be a genuine part of rural development programmes they must help in bringing about improvement in standards of living of rural societies, including their overall health. This will require a broader approach and more confrontation between the various agencies and disciplines involved….”
    Well, you can get as much benefit by controlling diesel exhaust as by replacing home cooking setups, and that’s far fewer point sources to fix — but who pays?  Look at the Port of Oakland experience, again collateral damage arises:

  2. Tom Fuller says:

    France and a couple of the Northern European countries burn an awful lot of wood for domestic heating. Quick fix there. There are several initiatives to replace the three stone oven in the developing world. Potential quick fix there.
    Converting buses to natural gas is expensive in the developed world–I think it cost £55K to do one bus in the UK, although it was a pilot project.
    But I think the easiest path to success would also be the most controversial. Making coal cleaner provides a lot of benefits, but a lot of people just don’t want that to happen at all.

  3. […] more from the original source:  Collide-a-scape » Blog Archive » Collide-a-scape >> The Low … By admin | category: University of HELSINKI | tags: black-carbon, climate, hartwell, […]

  4. Keith Kloor says:


    Re your “easiest path to sucess”: so called clean coal (which should be pursued) seems way, way off in the horizon. Reducing black soot, by contrast is something that can be done now–and cheaply.

  5. Tom Fuller says:

    Keith, I believe dirty coal is a major contributor to black soot, and existing best of breed coal fired plants have scrubbed an awful lot of it away–but there is active opposition to spreading best of breed tech into other coal plants. Part of it is choice of source of coal fuel, but a lot is how it’s burnt.

  6. Hank Roberts says:

    There’s a confusion between “clean coal” meaning co2 capture, and “clean coal” meaning “what we’re selling now” — the super-super-critical plants.

  7. Eli Rabett says:

    There actually is a health/climate change nexus on indoor cooking using dried cow droppings for fuel as is the practice in India. It is one of the major sources of the Asian “brown cloud” as well as a source of all sorts of respiratory disease. Unfortunately attempts to introduce better cooking stoves have floundered on the cost of fuel. The stuff they use now is as cheap as shit.  Oh, it is shit, and there are myriad very very poor people who spend their lives digging it up and drying it.
    There have been multiple attempts to design better stoves but they have all floundered on the the cost of fuels and the opposition to change.  This is not as “bright new idea” as you think and not as simple either

  8. James Hansen et al (2000): “An alternative scenario”

    “If sources of CH4 and O3 precursors were reduced in the future, the change in climate forcing by non-CO2 GHGs in the next 50 years could be near zero. Combined with a reduction of black carbon emissions and plausible success in slowing CO2 emissions, this reduction of non-CO2 GHGs could lead to a decline in the rate of global warming, reducing the danger of dramatic climate change.”
    Of course, Hansen is well aware that for the long run, reduction of CO2 emissions is paramount. But in this paper he argues that for the short term, reductions of non-CO2 climate forcings offer much more potential.

  9. Vinny Burgoo says:

    Eli #7, rocket stoves can burn dung these days and they cost almost nothing to make (partly because they can be partly made out of dung), so introducing them should be financially possible and wouldn’t have to put the dung-driers out of business. It’s win-win even without outside help, and NGOs and ‘carbon indulgence’-sellers are very keen on rocket-stove schemes (education, training, subsidies), so all in all it’s a bit of a mystery why their use isn’t more widespread.

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