Wood Smoke/Black Carbon Soot: A Major Cause of Global Warming
In the frenzied search for solutions to the global warming crisis, climatologists, policy makers
and other concerned environmentalists have overlooked one of the leading causes of rising
temperatures around the globe?soot---the black residue that coats fireplaces and darkens
vehicle exhaust. Black carbon soot may in fact be the second largest contributor to global
warming next to the greenhouse gas carbon dioxide.
According to Stanford environmental engineering Professor Mark Z. Jacobson, "Soot, or black
carbon, may be responsible for 15 to 30 percent of global warming, yet it is not even considered
in any of the discussions about controlling climate change." ('Nature', ScienceDaily, Feb. 9, 2001).
Jacobson also observed that human beings produce most of the soot particles that pollute the
atmosphere. He maintains that soot consists primarily of elemental carbon and that 90 percent
of it comes from the consumption of fossil fuels (particularly coal, diesel fuel, jet fuel, natural
gas, kerosene) and the burning of wood and other biomass. Jacobson also claims that a
worldwide reduction in soot emissions and controlling biomass burning could quell the alarming
pace of global warming and also reduce our reliance on soot-producing fuels.
( http://www.sciencedaily.com/releases/20 ... 075206.htm
Besides its impact on global warming, soot is bad for your health. The World Health
Organization reports that approximately 2.7 million people die each year from air pollution and
that reduction of wood and other biomass burning would not only mitigate global warming but
would also save lives and improve people's health.
Other studies have dispelled the myth that burning wood and other biomass is "green or carbon
neutral" and that the fine particulates emitted during the combustion process actually hasten
climate change. (www.burningissues.org
under both Science and Global Warming headings).
The warming effect of black carbon soot is far greater than previously estimated
Atmospheric scientist V. Ramanathan of the Scripps Institution of Oceanography and University
of Iowa chemical engineer Greg Carmichael found that "black carbon soot, from burning wood
and other biomass, cooking with solid fuels, and diesel exhaust has a warming effect in the
atmosphere three to four times greater than prevailing estimates." (Nature Geoscience 1, 221-227
(March 24, 2008). They calculated that soot and other forms of black carbon particulates may
represent as much as 60 percent of the current global warming effect of carbon dioxide and their
findings correlated with similar studies from Stanford, Caltech, and NASA.
A simplified explanation for the warming effect is that wood smoke's fine particulates thin
clouds. And as total airborne particulates increase, cloud cover decreases, allowing more
sunlight to reach the earth. According to Ramanathan, approximately 35 percent of black
carbon in the global atmosphere comes from China and India. Yet per capita emissions of black
carbon soot from the United States and some European countries is still comparable to those
from Asia. Ramanathan's research also found that the warming effects of black carbon smog
appear to be accelerating the melt of Himalayan glaciers that provide drinking water to billions
of people throughout Asia.
The International Global Panel on Climate Change (IGPCC) agreed that black carbon soot is a
major contributor to global warming
The 2007 Nobel-winning IGPCC panel of approximately two thousand scientists concluded that
black carbon soot has a dire atmospheric warming effect. Ramanathan and Carmichael's data
supported an even more alarming conclusion: That black carbon soot has an atmospheric
warming effect three to four times greater than previously thought. This was significant
because soot had previously been unaddressed as a major contributor to global warming.
Nor had the amplification of black carbon's warming effect been taken into account when mixed
with other aerosols, creating additional secondary fine particulates.
Studies of fine particulates from wood smoke in various communities
An EPA study cites that "In some neighborhoods, on some days, 90% of the particle pollution
is from residential wood burning." (Jane Koenig and Timothy Larson, A Summary of Emissions
Characterization and Non-Cancer Respiratory Effects of Wood Smoke,
USEPA DOC #453/R-93-036,1-919-541-0888).
A study in two San Jose, California locations showed that wood smoke pollution was 4.4 times
that of gasoline or diesel fueled vehicles. ("A Comparison of Source Apportionments of Fine
Particulate Matter at Two San Jose, CA Locations," from San Jose Speciation Trends Network.)
The next step
Because the urgency of reducing black carbon emissions cannot be overstated, reducing soot
from wood smoke would offer nearly instant benefits in improving atmospheric conditions in
the United States. It would also offer immediate societal and health benefits. This would
facilitate political and regulatory momentum towards mitigation of black carbon emissions.
It is urgent to advance public awareness of wood smoke's crucial role in global warming with
education and policy changes.
For those interested in more scientific and educational data about wood smoke, see
. The Burning Issues site was founded in 1988 as a special particulate
pollution project of the Bay Area Loma Prieta/Silicon Valley Chapter of the Sierra Club.
Occupation: Realtor, Coldwell Banker/Burnet, Minneapolis, Minnesota
Midwest Director, Clean Air Revival
Sierra Club member