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Reducing Black Carbon Emissions and Ground-Level Ozone Would Provide Immediate Benefit Against Climate Change

Reducing emissions of black carbon soot and ground-level ozone would quickly make a considerable dent in the climate change problem and would also contribute to public health and protect crop yields, according to an essay in the September/October issue of Foreign Affairs.

The piece was co-authored by Scripps Institution of Oceanography at UC San Diego climate and atmospheric scientist V. Ramanathan and Jessica Seddon Wallack, director of the Center for Development Finance at the Institute for Financial Management and Research in Chennai, India.

Right now the world is looking at well over a 2 degree rise in temperatures from the pre-industrial age. To avoid the severe consequences associated with such a dramatic change, we need to look at other feasible complementary measures, in addition to reducing CO2 emissions, that will provide near-term mitigation.

—V. Ramanathan

Ramanathan concludes that full implementation of existing emissions-control technologies could offset the warming effects of one to two decades of carbon dioxide emissions.

A dedicated effort would not only allow more time for creation of effective carbon dioxide-reduction regulations but would also have enormous public health and economic benefits, the authors said.

  • Black carbon is produced largely by diesel vehicles and the burning of biomass, including in cookstoves in developing countries like China and India. It contributes to 7% of child deaths worldwide that result from fatal respiratory infections. Black carbon is also responsible for almost 50% of warming in the Arctic as well as extensive snow and ice melt in the Himalayas. Available technology such as diesel particulate filters for vehicles and cleaner- burning biomass and solar cookstoves can significantly reduce black carbon emissions.

  • Ground level or tropospheric ozone (different than the stratospheric ozone that blocks the sun’s UV rays) is formed by ozone precursor gases such as carbon monoxide, nitrogen oxides, methane, and other hydrocarbons. Improving the efficiency of industrial and transportation combustion processes can reduce these gases. Besides a danger to breathe, ozone lowers crop yields. A recent study reported that ozone’s damage to crop yields in 2000 resulted in an economic loss of $14-26 billion annually.

Focusing on reducing emissions of black carbon and ozone precursors is the low-hanging fruit: the implementation is feasible, and the benefits would be numerous and immediate.

—Wallack and Ramanathan

Ramanathan said that he and his coauthor approached Foreign Affairs with the concept for the article based on his calculations in a 2008 paper that society has already crossed the threshold at which damaging effects of climate change are assured. (Earlier post.) He also approached Wallack, a policy expert, to suggest ways of presenting the challenge and possible responses that reach audiences that could implement new regulations and effect initiatives to make cleaner technologies more accessible.

Both black carbon particles and ozone gas remain in the atmosphere for periods of only weeks to months, as opposed to the centuries that carbon dioxide remains in the atmosphere. The authors argue that mitigation measures targeting black carbon and ozone would therefore produce immediate climate benefits. Additionally it would help alleviate damage to respiratory health in humans caused by black carbon smog, the fourth-leading cause of premature death in developing countries. Crop yields would be aided by ozone-removal efforts since the gas damages plant cells and disrupts chlorophyll production.

Wallack and Ramanathan further point out that technologies to reduce black carbon and ozone already exist. The authors cite a finding from an American non-profit research organization that shows that retrofitting one million tractor-trailers with diesel particulate filters would produce effects equal to removing 5.7 million cars from the road. The main challenges, according to the authors, lie in motivating adoption of technologies to reduce diesel emissions and making technologies to burn biomass fuels more efficiently accessible around the world. These are more akin to development challenges than traditional environmental policies.

Ramanathan said that these mitigation measures could serve to hedge against the full effects of global warming caused by greenhouse gases. They will also offset the acceleration of global warming that can occur when the atmosphere is cleaned of reflective particles such as sulfates from coal combustion that have an atmospheric cooling effect.

Diesel exhaust and cooking with biomass fuels both have net warming effects, though the magnitude of biomass burning’s warming effect is not well understood. Ramanathan is currently studying the net warming effect of biomass burning as part of Project Surya, an effort to measure the effect of replacing traditional cooking methods in rural India with cleaner-burning alternatives. Wallack and UCSD Rady School of Business Professor Vish Krishnan are also participating in Project Surya to identify ways to remove bottlenecks to larger-scale adoption of technologies for cleaner burning of renewables.

Our finding provides a tremendous incentive to help the over 3 billion people who live on less than $2 a day and are forced to cook and heat their homes with biomass fuels such as dung, crop residues and firewood.

—V. Ramanathan

US Senators Tom Carper (D-DE), Jim Inhofe (R-OK), Barbara Boxer (D-CA) and John Kerry (D-MA) introduced a black carbon bill earlier this year, as did Congressmen Jay Inslee (D-WA), Peter Welch (D-VT), and Mike Honda (D-CA). A provision on black carbon is also included in the Waxman-Markey climate bill.




more human-made mess to clean up?


Guess we all have to eat raw food and become flatulent free.

Aureon Kwolek

The article above calls our attention to “direct” ways to mitigate warming and climate change – reducing black carbon soot particles.

Professor Kimberly Prather, Department of Chemistry and Biochemistry, and Scripps Institution of Oceanography, University of California, San Diego - has recently documented that sulfate aerosols commonly bond to black carbon soot particles. Prior to this we thought that sulfate aerosols had a reflective and cooling affect. Now the reverse is true, because sulfate aerosols and black carbon are produced together, and they rapidly bond.

Black carbon particles suspended in air for 1 to 3 weeks is the first effect. In addition to being a serious respiratory health hazard, this produces a warming affect, because the sulfate acts as a lens around the black carbon - That amplifies solar thermal absorption 1.6 times. See: “Sulfate Lens Enhances Climate Warming Properties of Atmospheric Soot” (Green Car Congress). The second effect is when black carbon soot falls on the surface of land, sea, ice and snow. That can cause additional solar thermal absorption. It can also melt snow and ice and contribute to acidification.

Sulfate bonds with black carbon soot when we burn common diesel fuel, bunker fuel, jet fuel, heating oil, wood or pellets, garbage, kerosene, gasoline, coal, and even biomass (not a complete list). The entire earth is literally being sprayed with black carbon soot, 24 hours a day. Our first priority should be to mitigate black carbon soot, a much bigger bang for the buck than CO2.

Scrubbing diesel exhaust is a worthy cause, but that will only fix part of the problem. We should scrub all fossil fuel exhaust - especially ships burning bunker. See: “Commercial Shipping Emits Almost Half as Much Particulate Pollution as Total Released by World’s Cars” (Green Car Congress).

Scrub commercial jets. Military vehicles and aircraft too. We should gradually ban ships entering our waters that are burning sulfurous fuels or not filtering black carbon soot out of their exhaust. Same with commercial aircraft. You can’t dock or land in our country, unless you comply. This would prompt owners of older technology to retrofit or upgrade, if they want to do business in your country.

We should ban the burning of garbage and other refuse, especially in rural areas. And we should gradually require heating oil units, woodstoves, and fireplaces to have exhaust filtration systems, and phase-out the old technology. We should go after all the low-hanging fruit - Not get tangled-up in the unintended consequences and the costly bureaucracy of cap and trade.

Mitigating 22X methane at land fills, sewage disposal plants, septic systems, and sources of animal manure is another one.

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