A Vietnamese woman cooks over an open flame in her house. Up to 3 billion people worldwide rely on solid fuels such as wood, coal, crop waste or animal dung for indoor cooking and heating. Photo by Chitose Suzuki:AP

As the question of what the United States will do to address global warming is debated, the issue of soot has suddenly been discovered. Last month, the New York Times published a major article about soot, focusing on the mud cookstoves of Indians in Kohlua, India, about a two-hour bus ride away from Agra, the home of the Taj Mahal, where many of the residents work. The stoves are fueled by twigs or dung and emit dense clouds of smoke that leave coats of black grime on the undersides of the thatched roofs and a brown cloud over the landscape.

In Kohlua, there are virtually no cars and little electricity, so emissions of carbon dioxide, the main heat-trapping gas linked to global warming are near zero. But soot, also known as black carbon, is emerging as a major source of global climate change. What was amazing about the Times’ article was the writer’s continued reference to soot/black carbon being an unappreciated source of global climate change.

The reporter wrote:

“But the awareness of black carbon’s role in climate change has come so recently that it was not even mentioned as a warming agent in the 2007 summary report by the Intergovernmental Panel on Climate Change that pronounced the evidence for global warming to be 'unequivocal'.” Mark Z. Jacobson, professor of environmental engineering at Stanford, said that the fact that black carbon was not included in international climate efforts was 'bizarre', but 'partly reflects how new the idea is.' The United Nations is trying to figure out how to include black carbon in climate change programs, as is the federal government.

Before digging into the subject of soot and its impact on the visible evidence of global warming, we would offer two thoughts about the reporter’s observations. First, if the reporter, Elisabeth Rosenthal, had done any research she would have uncovered numerous reports and studies about soot and its impact on global warming, which of course raises issues about the UN’s IPCC’s focus.

Were they truly concerned about addressing issues dealing with global warming/climate change, or were they motivated by some other agenda? Second, the fact that Europe and the United States do not suffer from soot problems to the degree that underdeveloped and developing economies do means that there is little federal money here for research to solve a problem that has already been eliminated. That seems to support the off-the record observations of people we have talked to about the global warming/climate change issue – it’s all about the money!

Rosenthal was sent into the field to do research to back up the newspaper’s global warming coverage as part of a planned series of articles on the subject. She ventured to India to visit with Dr. Veerabhadran Ramanathan, one of the world’s leading climate scientists who is a professor of climate science at the Scripps Institute of Oceanography. He is currently in India working with the Energy and Resources Institute in New Delhi on a project to help poor families acquire new cookstoves. He believes the planet is driving rapidly toward an environmental cliff. Eliminating soot would be an easy step in addressing a cause of global warming while buying time for the world to mobilize and address the bigger issue of global warming/climate change – regulating the emissions of carbon dioxide.

The principal source of black carbon in Asia and Africa is cookstoves fueled by wood, coal and dung, although black carbon also comes from the operation of diesel engines and coal-fired power plants there. In the US and Europe, black carbon from engines and power plants has largely been eliminated by the use of filters and scrubbers before the effluent is released into the atmosphere. The impact of black carbon from cookstoves on Asia’s air quality is shown by the following computer generated maps based on data extrapolated from satellite pollution measurements collected by the Scripps Institute.

While carbon dioxide is considered the leading factor in global warming, scientists are now recognizing that black carbon is the second most important factor. Black carbon is estimated to be responsible for 18 percent of the planet’s warming compared to 40 percent for carbon dioxide. Converting to low-soot cook stoves would remove the warming effects of black carbon quickly; shutting a coal powered electricity plant would take years to reduce the global carbon dioxide concentrations that are in the atmosphere.

How significant is black carbon in the global warming/climate change picture? One recent study estimated that black carbon might account for as much as half the Arctic warming. What climate scientists are beginning to recognize is that while particles of soot tend to settle over time and do not have the global reach of greenhouse gases, they do travel. Soot from India has been found in the Maldives and on the Tibetan Plateau; from the US it travels to the Arctic. The impact of soot emissions can be enormous. According to Prof. Syed Iqbal Hasnain, a glacier specialist from the Indian state of Sikkim, Himalayan glaciers are expected to lose 75 percent of their ice by 2020.

These glaciers are a source of most of the major rivers in Asia. The short-term impact of the melting ice is severe flooding in the mountain regions. The number of floods from glacial lakes is already rising according to Hasnain. After the glaciers shrink, Asia’s big rivers will run low or dry for part of the year and battles over water will likely add to the geopolitical conflicts in the region.

A major issue about black carbon and the population is its health impact. Breathing the smoke from these biomass fires results in black carbon entering people’s lungs and damaging them and often causing death. We know that as long ago as 1900, The Chicago Tribune published articles detailing the impact of black carbon on the lungs of citizens of that city. In March, a bill was introduced in Congress that would require the Environmental Protection Agency to specifically regulate black carbon and direct aid to black carbon reduction projects overseas, including providing cookstoves to as many as 20 million homes. The new stoves cost about $20 and use solar power or are more efficient when fueled with biomass. The reduction in soot emissions from the new cookstoves is about 90 percent.

Again we circle back to the revelation that soot is a new global warming/climate change phenomenon, at least from the reporter’s viewpoint and some of her climate scientist contacts. After reading the report we dug through some of our old files and uncovered some articles about soot dating back to 2005. We were very intrigued by one report that included pictures of a backyard demonstration of the impact of soot on snow. While backyard snow is not the same as glacier ice, the demonstration makes the point clearly.

The demonstration was conducted by Roger Pielke Sr., a well-known and respected climatologist having held many high level climate and meteorological positions during his career and the author of over 300 research papers and nine books, who is currently semi-retired but remains a senior researcher at the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado in Boulder. His information was presented on a weblog provided by Mike Smith, the CEO of WeatherData Services, Inc. an AccuWeather Company.

Pielke began by explaining the concept of “albedo,” which is defined as: The ratio of the outgoing solar radiation reflected by an object to the incoming solar radiation incident upon it.” Fresh, pure white snow has an albedo of nearly 100 percent. In other words, just about all of the solar energy striking the snow is reflected back into space. Since the heat is reflected rather than absorbed, the solar energy has relatively little melting effect on pure white surfaces. It is why people wear white clothes more frequently during the summer and in tropical climates in an attempt to remain cool.

If the color of the snow is darkened by soot, the albedo drops dramatically. The soot absorbs some of the radiation that otherwise would have been reflected, thus heat is transferred from the soot into the snow resulting in an acceleration in the rate of melting.

Importantly, the heat transfer can cause melting to increase even if the ambient temperature remains constant, i.e., why snow can melt even in sub-zero temperatures.

Pielke tossed some eight month-old fireplace ash on fresh snow in his backyard one December day when the sky was totally blue. The demonstration occurred two days after the winter solstice when the albedo effect is less than it would have been under clear skies in February or March. In just one hour, the greater melting of the ash-covered areas becomes readily apparent. After four hours, the ash-free area has a depth of 5.5 inches. At the same time, the ash-covered areas have a depth of about 2.5 inches.

The areas without soot melt about 0.5 inches of snow in the four-hour period while the soot-covered areas melt 3.5 inches The areas without soot melt about 0.5 inches of snow in the four- hour period while the soot-covered areas melt 3.5 inches. Dr. Pielke suggests that any discussion about melting glaciers must consider the accelerated melting caused by soot pollution in addition to any contribution from changing ambient temperatures.

The problem is that correcting soot pollution, which could have a very significant impact on the world’s glaciers, doesn’t feed global warming/climate change scientists’ families.