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Black carbon, commonly described as soot, may play a larger role in global warming than previously estimated, according to a new study.
Every year in the Northern Hemisphere about 7.5 million metric tons of black carbon, the equivalent of more than 100 times Earth’s total biomass, enters the air from internal combustion engines, forest fires and other sources. The fine material absorbs sunlight almost as well as carbon dioxide—a well-known greenhouse gas—and may contribute to accelerated snowmelts and increased global temperatures.
"We’re trying to figure out how to deal with the greenhouse gas problem " says Sarah Doherty, an atmospheric scientist at the University of Washington in Seattle and co-author of the study. The new findings suggest that black carbon mitigation should be part of that strategy.
Scientists have known about the warming potential of black carbon for years, but Doherty's study, published yesterday in the Journal of Geophysical Research: Atmospheres, suggests previous calculations underestimated its impact. Doherty and her colleagues used a compilation of dozens of climate models to look at the life span of atmospheric black carbon. By imputing observational data recorded around the world, they studied the effect this pollutant might have on the Northern Hemisphere.
By itself, black carbon is a warming agent; however, it is not usually emitted in a pure form. Instead, black carbon is expelled into the atmosphere combined with other compounds such as sulfates, which affect their heat-absorbing and reflective properties. Black carbon could be seen as chocolate chips in baking, Doherty says by way of analogy. "In one case you put them in molasses cookies, and the other case you put them in sugar cookies." The result: cookies with different tastes and textures.
For example, black carbon from diesel engines is known to cause atmospheric warming because it is mixed with sulfates, says study co-author Tami Bond, an atmospheric scientist at the University of Illinois at Urbana–Champaign. Forest fires in the lower latitudes, however, are actually beneficial sources of black carbon because it is coupled with organic aerosols and ends up reflecting light and heat, causing the surrounding area to cool.
Atmospheric black carbon’s impact on climatic warming also varies due to its altitude. The team discovered that the consequences of black carbon and whether it promotes or combats climate change depend on its position—above, below or in the middle of cloud cover: Above the clouds, where the particulates absorb heat more readily, they produce a warming effect; below the cloud deck heat absorption is less significant.
Such disparities cause problems for scientists trying to describe the atmospheric effects accurately. According to the study, black carbon compounds have the potential to decrease the world's average temperature by 0.5 degree Celsius or warm it by 1.08 degrees C, depending on how it was produced. Previous studies lacked the observational data included in Doherty’s analysis, making earlier estimates much less accurate. Thus, policymakers have to consider the source of black carbon when drafting mitigation ordinances, Doherty says.
Although researchers still debate the overall influence of black carbon on the atmosphere, scientists do agree that it has become a serious health issue for populations on the ground. Inhaling black carbon could aggravate serious chronic illnesses such as asthma.
Because black carbon only remains in the atmosphere for about a week, decreasing emissions translates into immediate health benefits. The rapid change could also prove a victory for world leaders trying to rally support for climate policy. "Once you stop the emissions, it’s gone. It’s a public health win," Bond says. "We can begin [combating climate change] by doing things for climate that people want to do because it has other health benefits."
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16 Comments
Add CommentIf black carbon only remains in the atmosphere for about a week how can it be a contributory factor in "Global Warming"? Atmospheric carbon is a localized low altitude factor contributing to beneficial "Spot Warming".
Reply | Report Abuse | Link to thisMollie Bloudoff-Indelicato
Reply | Report Abuse | Link to thisWhat is your source on the biomass of earth? You wrote,
"Every year in the Northern Hemisphere about 7.5 million metric tons of black carbon, the equivalent of more than 100 times Earth’s total biomass, enters the air from internal combustion engines, forest fires and other sources."
However, all estimates I have found estimate the biomass on earth in the range of billions to tens of billions metric tons carbon of total earth biomass. I am much more apt to believe this, as it comes from scientific sources. Looking at other sources I think you may merely have a typo, and wrote "7.5 million" where is should be "7.5 trillion". I would still be interested to know who did the study that arrived at this number so I can see how it was done.
I'm glad that someone is finally writing about other compounds, besides CO2, that may be contributing to global warming. I think this helps the debate and better isolates what actions humans can take to have the greatest impact in reducing any of our negative contributions to the environment. It may be easier and more economically advantageous to eliminate soot than to eliminate CO2.
I've been saying for years that we should be more concerned with pollution that we can actually do something about, as opposed to concentrating on CO2, which our efforts amount to raising taxes on.
Reply | Report Abuse | Link to thisOh yeah - I almost forgot carbon credits. Talk about making money from nothing.
It contributes to climate change because we continually pump black carbon out and it settles on ice, for instance, making it melt quicker, or it floats above the cloud deck, absorbing solar radiation. It is NOT limited to just low altitudes and drifts on global air currents.
Reply | Report Abuse | Link to thisIn addition, how is "spot warming" always beneficial? If you are in a city already suffering from the heat island effect and greenhouse gases are slowly raising average temperatures, "spot warming" due to the high concentration of black carbon on the buildings, streets, plants and in the air will not be strictly beneficial.
Lowering black carbon will only buy us some time to deal with steadily-rising CO2 concentrations. Thinking that climate change will be solved by dealing with only the black carbon problem is missing the bigger picture. The one advantage of dealing with black carbon is that it doesn't have dedicated industry groups, lobbyists and "think" tanks spreading misinformation about it yet.
Reply | Report Abuse | Link to thisBut since CO2 concentrations drive our long-term climate problem, ignoring it would be like not seeing the deforested forest for the trees that used to be there. If CO2 concentrations continue to increase like they are currently, all the gains made from reducing black carbon and then some will be swept under by steadily increasing temperatures.
Reply | Report Abuse | Link to this@sault
Reply | Report Abuse | Link to thisI don't think that dealing with black carbon will completely solve the problem, but its a start. It is much more practical to do what we can, and what's reasonable first then find ways to solve the other problems. Perhaps the solution to reducing the release of black carbon will also result in better scrubbers for CO2; you never know. Don't underestimate the economics of preventing CO2 emissions. If we want to eliminate CO2 completely then we will lose 60% of our electricity capacity. Neither solar or wind could replace fossil fuels because it would take a land area larger than Texas and cost more than the national GDP, which is not feasible. The only reasonable replacement then is nuclear, and that would require 200 new plants and would severely push up the date at which the nuclear fuel cycle needs to be closed (i.e. breed new fuel) before we run out of nuclear fuel or need to find new ways to obtain fuel; possibly from the ocean. Right now, whether we like it or not, we need fossil fuels. The best strategy towards reducing our impact is to concentrate on those pollution sources we can control and work on efficiency in electricity, manufacturing, and automotive vehicles. The great thing about efficiency is that it can pay for itself, in that companies that find cost effective measures to increase efficiency can reduce cost and increase profit margins. This also applies to coal and gas power plants. If coal and gas plants can increase plant efficiency then they have to buy less fuel to produce the same power; as a result they pollute less.
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Reply | Report Abuse | Link to thisIf we want ANY "economics" on CO2 to kick in, we'll have to put a price on it. $20 per ton is a good start and we can ratchet it up from there as we implement more energy efficiency and clean energy. Nobody seriously looking at this issue says we need to do it overnight, so claiming that "we will lose 60% of our electricity capacity[sic]" is not a sensible conclusion.
Reply | Report Abuse | Link to thisWhere are the numbers and calculations you used to determine "Neither solar or wind could replace fossil fuels because it would take a land area larger than Texas and cost more than the national GDP..."?
We can provide all the world's electricity with solar alone using less than 1% of global land area:
http://wwf.panda.org/wwf_news/?207268/Solar-PV-power-in-harmony-with-nature--new-WWF-report-says-land-requirements-are-insignificant
Farm and range land inside wind farms is still 90 - 99% productive for their original purpose(s). Farmers and ranchers are also very eager to get lease payments from wind turbines on their property.
Since coal power alone causes between $100B and $500B in YEARLY damages (health problems, reduced worker productivity, property damage, premature death, etc.) How is it feasible to flush that much money down the toilet every year?
http://pubs.aeaweb.org/doi/pdfplus/10.1257/aer.101.5.1649
http://onlinelibrary.wiley.com/doi/10.1111/j.1749-6632.2010.05890.x/abstract
Nobody has yet commented on the resultant CO2 climate sensitivity, considering the proportion of warming attributed to soot. The debate on CO2 depends, on the temperature rise, from a doubling of CO2. Soot has now grabbed a good section of that calculation, which has two effects:
Reply | Report Abuse | Link to thisIndicates the climate community was wrong about the magnitude of CO2 effect.
All present model's "projections" are wrong.
I believe that is exactly the skeptic message, for years, although an apology from all the doomsayers, will not be forthcoming, I'm sure. GK
Sault
Reply | Report Abuse | Link to thisPlease read more before drawing conclusions. http://www.agu.org/news/press/pr_archives/2013/2013-01.shtml
A much better conclusion would be that black carbon was a major contributed over a 1/3rd of warming experienced to date.
This would seem to lead reasonable people who are concerned about a warmer climate to a couple of conclusions.
1. Black carbon emissions should be attacked and reduced
2. Long term, it appears that CO2 plays a smaller role than was initially thought in overall warming by Hansen etc.
I would love to subscribe, but this is a perfect example of the left wing drival they promote as real Science. Everything they say or do is tainted with left wing politics. Its sad!
Reply | Report Abuse | Link to thisYes, rather similar to that "black lung" nonsense the coal miners cooked up...
Reply | Report Abuse | Link to thisBlack carbon is constantly being emitted so despite its short life in the atmosphere there is always plenty of it. All the spots add up. And once it falls out on ice or snow it stays pretty much on top until there is new snow.
Reply | Report Abuse | Link to thisDoing something about black carbon might give some time to find a better way to deal with carbon dioxide.
Reply | Report Abuse | Link to thisOK, so what is "Healthy Soot"?
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