Foreign Policy Blogs

Black Carbon and Solar Cookers

I touched on an important subject here earlier in the month when I mentioned a new study purporting that the spread of black carbon , or soot , from industrial and transportation sources, and from developing world cooking practices, is having a significantly more potent impact on climate change than previously thought. This release from the Scripps Institution of Oceanography discusses the work done by their highly regarded atmospheric scientist Veerabhadran Ramanathan and University of Iowa chemical engineer Greg Carmichael. They report that black carbon ” has a warming effect in the atmosphere three to four times greater than prevailing estimates.” What is also evident is that “Between 25 and 35 percent of black carbon in the global atmosphere comes from China and India, emitted from the burning of wood and cow dung in household cooking and through the use of coal to heat homes. Countries in Europe and elsewhere that rely heavily on diesel fuel for transportation also contribute large amounts.” This article, Dust plays huge role in climate change, from the “Christian Science Monitor,” explains it well. There’s an accompanying podcast here from the reporter as well.

See also The even darker side of brown clouds from “Nature Reports Climate Change” and the scientists’ report itself, Global and regional climate changes due to black carbon, in “Nature Geoscience.” They say here that “The interception of solar radiation by atmospheric brown clouds leads to dimming at the Earth’s surface with important implications for the hydrological cycle, and the deposition of black carbon darkens snow and ice surfaces, which can contribute to melting, in particular of Arctic sea ice.” This is true for the Himalayan region as well. Ramanathan and Carmichael further say that since ” BC has a significant contribution to global radiative forcing, and a much shorter lifetime compared with carbon dioxide (which has a lifetime of 100 years or more), a major focus on decreasing BC emissions offers an opportunity to mitigate the effects of global warming trends in the short term. Reductions in BC are also warranted from considerations of regional climate change and human health.”

We have known for some time about the health effects of soot in urban environments and in rural villages where cooking accounts for hundreds of thousands of deaths annually, mostly of women and young children, according to any number of studies. See this study from the “Proceedings of the National Academy of Sciences” (PNAS), and an accompanying group of studies, for instance, on the disastrous health effects of biomass burning for cooking in the developing world. According to the World Health Organization, “More than three billion people worldwide continue to depend on solid fuels, including biomass fuels (wood, dung, agricultural residues) and coal, for their energy needs.”

See this graphic from the Ramanathan and Carmichael report to illustrate the extent and the impact of the biomass burning.


[The polluting effects of cooking using biomass like wood or cow dung in South Asia are illustrated through a measurement of aerosol optical depth, a way of measuring the quantity of pollutants in the air by the relative ability of light to penetrate through them. The upper image is a representation showing reconstructed levels of pollution from 2004 and 2005. The bottom image is a representation with the effects of biofuel cooking removed.]

How do we address the soot from household use, thus radically reducing the human health impacts and the radiative forcing from the atmospheric brown clouds and the BC deposition? One way is to eliminate biomass from cooking. The use of solar cookers is one stunningly effective and, hopefully, burgeoning approach in the developing world. Solar Cookers International is the truly superb NGO that has been spreading the word and the technology both among international aid agencies and on the ground in the developing world for a number of years now. See this powerpoint show for an introduction and use their website to learn more. They are, as just one example of many, working with the U.N. High Commissioner for Refugees to equip refugees from the fighting in Darfur with the equipment and the know-how to go nearly entirely solar for cooking. One of the strongest indications of the success of their approach is the near total acceptance of solar cookers by the women of these camps.

SCI is doing amazing, critically important work, and it is incumbent on those of us concerned about sustainable development to learn more and support exactly these sorts of efficient, cost-effective and easily deployable technologies. It’s not always all about the high tech, capital intensive projects.



Bill Hewitt

Bill Hewitt has been an environmental activist and professional for nearly 25 years. He was deeply involved in the battle to curtail acid rain, and was also a Sierra Club leader in New York City. He spent 11 years in public affairs for the NY State Department of Environmental Conservation, and worked on environmental issues for two NYC mayoral campaigns and a presidential campaign. He is a writer and editor and is the principal of Hewitt Communications. He has an M.S. in international affairs, has taught political science at Pace University, and has graduate and continuing education classes on climate change, sustainability, and energy and the environment at The Center for Global Affairs at NYU. His book, "A Newer World - Politics, Money, Technology, and What’s Really Being Done to Solve the Climate Crisis," will be out from the University Press of New England in December.

Areas of Focus:
the policy, politics, science and economics of environmental protection, sustainability, energy and climate change