Cooperative Institute for Research in Environmental Sciences


A recent increase in the abundance of particles high in the atmosphere has offset about a third of the current climate warming influence of carbon dioxide (CO2) change during the past decade, according to a new study led by Susan Solomon, a Fellow with the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder. The study was published July 21 in the online edition of Science. In the stratosphere, miles above Earth’s surface, small, airborne particles reflect sunlight back into space, which leads to a cooling influence at the ground. These particles are also called “aerosols," and the new paper explores their recent climate effects—the reasons behind their increase remain the subject of ongoing research.

“Since the year 2000, stratospheric aerosols have caused a slower rate of climate warming than we would have seen without them,” says John Daniel, a physicist at the NOAA Earth System Research Laboratory (ESRL) in Boulder, Colo., and an author of the new study.

The new study focused on the most recent decade, when the amount of aerosol in the stratosphere has been in something of a “background” state, lacking sharp upward spikes from very large volcanic eruptions. The authors analyzed measurements from several independent sources—satellites and several types of ground instruments—and found a definitive increase in stratospheric aerosol since 2000.

“Stratospheric aerosol increased surprisingly rapidly in that time, almost doubling during the decade,” Daniel said. “The increase in aerosols since 2000 implies a cooling effect of about 0.1 watts per square meter—enough to offset some of the 0.28 watts per square meter warming effect from the carbon dioxide increase during that same period.”

The reasons for the 10-year increase in stratospheric aerosols are not fully understood and are the subject of ongoing research, says coauthor Ryan Neely, with CIRES. Likely suspects are natural sources—smaller volcanic eruptions—and/or human activities, which could have emitted the sulfur-containing gases, such as sulfur dioxide, that react in the atmosphere to form reflective aerosol particles.

Daniel and colleagues with NOAA, CIRES-University of Colorado Boulder, NASA and the University of Paris used a climate model to explore how changes in the stratosphere’s aerosol content could affect global climate change—both in the last decade, and projected into the future. The team concluded that models miss an important cooling factor if they don’t account for the influence of stratospheric aerosol, or don’t include recent changes in stratospheric aerosol levels.

Moreover, future global temperatures will depend on stratospheric aerosol. The warming from greenhouse gases and aerosols calculated for the coming decade can vary by almost a factor of two—depending on whether aerosols continue to increase at the same rate as over the past decade, or if instead they decrease to very low levels, such as those experienced in 1960.

If stratospheric aerosol levels continue to increase, temperatures will not rise as quickly as they would otherwise, said Ellsworth Dutton, also with NOAA ESRL and a coauthor on the paper. Conversely, if stratospheric aerosol levels decrease, temperatures would increase faster. Dutton and his colleagues use the term “persistently variable” to describe how the background levels of aerosol in Earth’s stratosphere can change from one decade to the next, even in the absence of major volcanic activity.

Ultimately, by incorporating the ups and downs of stratospheric aerosols, climate models will be able to give not only better estimates of future climate change, but also better explanations of past climate changes.

“The ‘background’ stratospheric aerosols are more of a player than we thought,” said Daniel. “The last decade has shown us that it doesn’t take an extremely large volcanic eruption for these aerosols to be important to climate.”

Authors of the paper are: Susan Solomon, CIRES-University of Colorado Boulder; John Daniel, Chemical Sciences Division of NOAA’s Earth System Research Laboratory; Ryan Neely, CIRES-University of Colorado Boulder and NOAA-ESRL; J.P. Vernier, NASA-Langley Research Center and University of Paris; Ellsworth Dutton, Global Monitoring Division of NOAA-ESRL; and Larry Thomason, NASA-Langley.

Contact: 

Jana Goldman, NOAA, 301-734-1123, jana.goldman@noaa.gov

Kathleen Human, CIRES, 303-735-0196, kathleen.human@colorado.edu


Carbon dioxide remains the undisputed king of climate change, but other greenhouse gases measurably contribute to the problem, says a new study conducted by scientists from the Cooperative Institute for Research in Environmental Sciences (CIRES) and the National Oceanic and Atmospheric Administration (NOAA). The study, published August 3 in Nature, shows that cutting emissions of those other gases could slow changes in climate that are expected in the future.

Discussions with colleagues around the time of the 2009 United Nations’ climate conference in Copenhagen inspired three scientists—NOAA scientist and CIRES Fellow Stephen Montzka, Ed Dlugokencky and James Butler of NOAA—to review the sources of non-carbon dioxide (CO2) greenhouse gases and explore the potential climate benefits of cutting their emissions.

Like CO2, other greenhouse gases trap heat in Earth’s atmosphere. Some of these chemicals have shorter lifetimes than CO2 in the atmosphere, however, cutting emissions would quickly reduce their direct radiative forcing—a measure of warming influence.

“We know that climate change is primarily driven by carbon dioxide emitted during fossil-fuel combustion, and we know that this problem is going to be with us a long-time because carbon dioxide is so persistent in the atmosphere,” said Montzka, “But lowering emissions of greenhouse gases other than carbon dioxide could lead to some rapid changes for the better.”

Scientists know that stabilizing the warming effect of CO2 in the atmosphere would require a minimum of 80 percent decrease of CO2 emissions—in part because some of the carbon dioxide emitted today will remain in the atmosphere for thousands of years. In contrast, cutting all long-lived non-CO2 greenhouse gas emissions by 80 percent could diminish their climate warming effect substantially within a couple of decades. Cutting both CO2 and non-CO2 greenhouse gas emissions could result in a decrease in the warming effect of greenhouse gases this century, the new paper shows.

For the new analysis, the researchers considered methane; nitrous oxide; a group of chemicals regulated by an international treaty to protect Earth’s ozone layer; and a few other extremely long-lived greenhouse gases currently present at very low concentrations.

The new review paper describes the major human activities responsible for these emissions, and notes that steep cuts (such as 80 percent) would be difficult. Without substantial changes to human behavior, emissions of the non-CO2 greenhouse gases are expected to continue to increase.

The climate-related benefits of reductions in non-CO2 greenhouse gases have limits, Montzka and his colleagues showed. Even if all human-related, non-CO2 greenhouse gas emissions could be eliminated today, it would not be enough to stabilize the warming influence from all greenhouse gases over the next 40 years – unless CO2 emissions were also cut significantly.

The scientists also noted in the paper the complicated connections between climate and greenhouse gases, some of which are not yet fully understood. The non-CO2 gases studied have natural sources as well as human emissions, and climate change could amplify or dampen some of those natural processes, Dlugokencky said. Increasingly warm and dry conditions in the Arctic, for example, could thaw permafrost and increase the frequency of wildfires, both of which would send more methane and carbon dioxide into the atmosphere.

“The long-term necessity of cutting carbon dioxide emissions shouldn’t diminish the effectiveness of short-term action. This paper shows there are other opportunities to influence the trajectory of climate change,” Butler said. “Managing emissions of non-carbon dioxide gases is clearly an opportunity to make additional contributions.”

Contacts:

Katy Human, CIRES,303-735-0196, kathleen.human@colorado.edu

Stephen Montzka, CIRES, 303-497-6657, stephen.a.montzka@noaa.gov

Figures courtesy of NOAA 


Experts, including scientists from universities and federal agencies, from throughout the vast Southwest region convened this week at CIRES to begin writing the Southwest Region Technical Report for the National Climate Assessment (NCA).

The Global Change Research Act of 1990 requires NCA to report to Congress and the President on the status of climate change science and relevant impacts across the United States. This effort entails integrating current scientific research results and identifying gaps in both the understanding and knowledge of climate science, impacts and responses.

To develop the Southwest Region Technical Report for NCA, the CIRES Western Water Assessment (WWA) hosted a workshop on August 1-4, 2011 to bring together potential authors and establish an outline for the report.

“This is a unique opportunity to work with some of the best scientific minds in the region, many of whom are at CIRES,” WWA director Brad Udall said. “Our challenge is to synthesize a wealth of climate science and present it in a useful way to decision makers in the Southwest.”

The report is expected to be completed and available to the public by summer 2012.


What do a herd of gazelles and a fluffy mass of clouds have in common? A mathematical formula developed by scientists from the Cooperative Institute for Research in Environmental Sciences (CIRES) and Israel’s Weizmann Institute links these seemingly disparate entities.  

The scientists have used the formula, which describes the population dynamics of such prey animals as gazelles and their predators, to model the relationship between cloud systems, rain and tiny floating particles called aerosols. This model may help climate scientists understand, among other things, how human-produced aerosols affect rainfall patterns. The research was published in the journal Proceedings of the National Academy of Sciences on July 24. 

Clouds are major contributors to the climate system. In particular the shallow marine stratocumulus clouds that form huge cloud decks over the subtropical oceans cool the atmosphere by reflecting part of the income solar energy back to space. CIRES Fellow Graham Feingold and Ilan Koren of the Weizmann Institute’s Environmental Sciences and Energy Research Department found that equations for modeling prey-predator cycles in the animal world were a handy analogy for cloud-rain cycles: Just as respective predator and prey populations expand and contract at the expense of one another, so too rain depletes clouds, which grow again once the rain runs out. And just as the availability of grass affects herd size, the relative abundance of aerosols – which “feed” the clouds as droplets condense around them – affects the shapes of those clouds. A larger supply of airborne particles gives rise to more droplets, but these droplets are smaller and thus remain high up in the cloud rather than falling as rain. 

In previous research, Feingold and Koren had “zoomed in” to discover oscillations in convective cells in marine stratocumulus. Now they returned to their data, but from a “top down” angle to see if a generalized formula could reveal something about these systems. Using just three simple equations, they developed a model showing that cloud-rain dynamics mimic three known predator-prey modes. Like gazelles and lions, the two can oscillate in tandem, the “predator” rain cycle following a step behind peak cloud formation. Or the two can reach a sort of steady state in which the clouds are replenished at the same rate as they are diminished (as in a light, steady drizzle). The third option is chaos – the crash that occurs when predator populations get out of hand or a strong rain destroys the cloud system. 

The model shows that as the amounts of aerosols change, the system can abruptly shifts from one state to another. The model shows a bifurcation –  two scenarios at different ends of the aerosol scale that lend themselves to stable patterns. In the first, relatively low aerosol levels lead to clouds in which development depends heavily on aerosol concentrations. In the second, high levels produce saturation; these clouds depend solely on the initial environmental conditions. 

Using this so-called systems approach, says Koren: “can open new windows to view and understand the emergent behavior of the complex relationships between clouds, rain and aerosols, giving us a more useful view of the big picture and helping us to understand how shifting aerosol levels can lead to different climate patterns.”
Press release courtesy of the Weizmann Institute of Science

Contact:

Graham Feingold, CIRES, 303-497-3098, graham.feingold@noaa.gov

Kathleen Human, CIRES, 303-735-0196, kathleen.human@colorado.edu

Ilan Koren, Weizmann Institute of Science, Israel, 972-8-934-2522, Ilan.Koren@weizmann.ac.il


Bacteria from fecal material—in particular, dog fecal material—may constitute the dominant source of airborne bacteria in Cleveland’s and Detroit’s wintertime air, says a new study led by researchers from the Cooperative Institute for Research in Environmental Sciences (CIRES).

The study, which was published July 29 in Applied and Environmental Microbiology, showed that of the four Midwestern cities in the experiment, two cities had significant quantities of fecal bacteria in the atmosphere—with dog feces being the most likely source.

“We found unexpectedly high bacterial diversity in all of our samples, but to our surprise the airborne bacterial communities of Detroit and Cleveland most closely resembled those communities found in dog poop,” said lead author Robert Bowers, a CIRES graduate student in CU Boulder’s Ecology and Evolutionary Biology department. “This suggests that dog poop may be a potential source of bacteria to the atmosphere at these locations.”

Scientists already knew that bacteria exist in the atmosphere and that these bacteria can have detrimental effects on human health, triggering allergic asthma and seasonal allergies, said CIRES Fellow Noah Fierer, who is also an assistant professor in CU Boulder’s Ecology and Evolutionary Biology department. But it is only in recent years that researchers have realized that there is an incredible diversity of bacteria residing in the air, he said.

“There is a real knowledge gap,“ Fierer said. “We are just starting to realize this uncharted microbial diversity in the air—a place where you wouldn’t exactly expect microbes to be living.”

To gain further understanding of just what microbes are circulating in urban environments, the team analyzed the local atmosphere in the summer and winter at four locations in the Great Lakes region of the U.S. Three of the locations—Chicago, Cleveland and Detroit—are major cities with populations greater than 2 million, and one location, Mayville, WI, is a small town with a population of less than 6,000.

The team used nearly 100 air samples, collected as part of a previous study, conducted by Colorado State University (CSU). The CSU experiment investigated the impacts of biomass burning (burning of trees or plant material) on air quality and involved studying the effect of residential wood burning and prescribed fires on airborne fine particle concentrations in the midwestern United States.

“What we’ve been looking at are the numbers and the types of bacteria in the atmosphere,” Fierer said. “We breathe in bacteria every minute we are outside, and some of these bugs may have potential health implications.”

The researchers analyzed the bacteria’s DNA in the collected air samples and compared the bacteria found against a database of bacteria from known sources such as leaf surfaces, soil and human, cow and dog feces. They discovered that the bacterial “communities” in the air were surprisingly diverse and also that, in two of the four locations, dog feces were a greater than expected source of bacteria to the atmosphere in the wintertime.

In the summer, airborne bacteria come from many sources—soil, dust, leaf surfaces, lakes and oceans, Bowers said. But in the winter, as leaves drop and snow covers the ground, the influence that these environments have as sources also goes down. It is during this season that the airborne communities appeared to be more influenced by dog feces than the other sources tested in the experiment, he said.

“As best as we can tell, dog feces are the only explanation for these results,” Fierer said. “But we do need to do more research.”

The team plans to investigate the bacterial communities in other cities and build a continental-scale atlas of airborne bacterial communities, Fierer said. “We don’t know if the patterns we observed in those sites are unique to those cities,” he said. “Does San Francisco have the same bacteria as New York? Nobody knows as yet.”

Fierer believes it is important to pin down the types of bacteria in the air; how these bacteria vary by location and season; and where they are coming from. With this information, scientists would then be able to investigate the possible impacts on human health, he said.

“We need much better information on what sources of bacteria we are breathing in every time we go outside,” Fierer said.

Co-authors on the study included Rob Knight an associate professor in CU Boulder’s Department of Chemistry and Biochemistry, Amy Sullivan and Jeff Collett Jr. of Colorado State University, and Elizabeth Costello of Stanford University School of Medicine. The study was funded by the CIRES Innovative Research Program, the U.S. Environmental Protection Agency, the National Science Foundation, the Howard Hughes Medical Institute and the National Institutes of Health. The Lake Michigan Air Directors Consortium (LADCO) supported the aerosol sample collection for the project.

Noah Fierer, CIRES, 303-492-5615, Noah.Fierer@colorado.edu

Jeff Collett, CSU, 970-491-8697, collett@atmos.colostate.edu

Kathleen Human, CIRES, 303-492-6289, kathleen.human@colorado.edu


CIRES Fellow Anne Sheehan who has studied earthquake activity in southern Colorado said she was not too surprised when a 5.3 magnitude quake struck about nine miles west of Trinidad last night about 11:46 p.m. “This particular area has had quite a few small earthquakes, especially in the past 10 years,” said CU Boulder Professor Anne Sheehan of the geological sciences department and the Cooperative Institute for Research in Environmental Sciences. “For Colorado, this is usually where the action is.”

The quake was the largest in Colorado in several decades and was felt from Fort Collins to Garden City, Kan. The earthquake occurred about nine miles southwest of Trinidad and about 180 miles south of Denver, according to the U.S. Geological Survey’s National Earthquake Information Center in Golden.

In 2006 Sheehan began a CU Boulder project sponsored by the National Science Foundation to place GPS instruments at 24 sites along the Rio Grande Rift in Colorado and New Mexico to measure the ground movement and earthquake potential, an effort that continues today. The Rio Grande Rift is a region that reaches from central Colorado to Mexico and is characterized by the spreading and thinning of Earth’s crust and associated with several moderate to large earthquakes dating back thousands of years.

In addition, CU Boulder has teamed with the state of Colorado to “adopt” several seismic instrument stations set up in Colorado as part of the NSF’s EarthScope effort, said Sheehan. One of the adopted stations is near Trinidad and was chosen because of the recent history of earthquake activity there. The project also involves Colorado College and Colorado State University. The results of the study are to be published in an upcoming edition of the journal Geology. Sheehan also can talk in general about the earthquake that struck near Washington, D.C., today.

For more information contact Sheehan at 303-492-4597 or afs@cires.colorado.edu. Or contact Jim Scott in the CU Boulder news services office at 303-492-3114.

For more information on Sheehan’s Rio Grande Rift project click here.


CIRES researchers from several divisions are attending the 242nd American Chemical Society National Meeting in Denver, Aug. 28–Sept. 1.

The scientists, including four CIRES Fellows—Lisa Dilling, Jose-Luis Jimenez, Ted Scambos and Margaret Tolbert —will present their novel research results at the conference themed ‘Chemistry of Air, Space and Water.’

The oral and poster presentations include the following:

• Ted Scambos will present: “Ice on Earth: Change is in the air.”

• Margaret Tolbert will present: “Importance of aerosol morphology for ice nucleating efficiency: Combined laboratory and field study.”

• Lisa Dilling will present: “Facilitating usable science: Experience from the use of seasonal climate forecasts.”

• Jose-Luis Jimenez will present: “Insights on the importance of different organic aerosol sources from field measurement, box and 3D modeling, and intensive property measurements.”

• Martin Graus will present: “Comparison of VOC emissions from conventional and alternative biofuel crops.”

For the full list of presenters and their abstracts click here.


CIRES main campus building was one of the 24 locations across the globe to host Al Gore’s “24 Hours of Reality” event yesterday evening.

A multimedia presentation — created by Gore, Nobel Laureate and former Vice President of the United States, and delivered by a presenter trained by Gore — was broadcast live online as part of the “24 Hours of Reality” project. The presentation told the stories of local people living with the impacts of a changing climate. Similar presentations screened each hour over 24 hours from twenty-four locations across the globe—such as New York, London, Mexico City, Jakarta and Tonga.

The project’s founders stated its mission was to: “Bring the facts about the climate crisis into the mainstream and engage the public in conversation about how to solve it.” Leading the presentation in Boulder was John Zavalney, an award-winning teacher who has worked in the Los Angeles public school system for more than 20 years. Zavalney, now at the San Pedro Science Center in Los Angeles, CA, became interested in climate change during his long career as an educator and has been involved in a variety of environmental education programs.

CIRES provided the venue to allow an outlet for one perspective of the climate debate; however the opinions, positions or statements expressed by the Climate Reality Project and those providing comments are theirs alone, and do not necessarily reflect the scientific perspectives of the Institute’s researchers.

The event was by Climate Reality Project invitation only because of space restrictions, but invited members of the local public attended.


The area covered by crevasses northeast of Ilulissat, West Greenland, has expanded by 13 percent over the last 24 years, according to scientists at the Cooperative Institute for Research in Environmental Sciences (CIRES)—a change that may impact the sliding of the Greenland Ice Sheet and subsequent sea level rise.

“The area covered by crevasses is increasing,” said CIRES research associate William Colgan, lead author of the study published online today in Geophysical Research Letters. “Theoretically, this change may cause the ice sheet to slide more slowly toward the coast or into the ocean.”

Colgan and his coworkers, a team led by CIRES Director Konrad Steffen at the University of Colorado Boulder, investigate the slide of the Greenland Ice Sheet, the second largest ice sheet on Earth. “People typically think of a block of ice as something really solid and inflexible,” Colgan said. “But when a block of ice is as big as the Greenland Ice Sheet, there is sufficient pressure from its weight to cause it to flow like a really, really slow river into the ocean.”

The weight of the ice causes the sheet to flow like a viscous fluid, and water between the ice sheet and its bed means the sheet slides as well as flows, Colgan said. The flow and sliding of the ice sheet can cause more ice than normal to flow into the ocean, which can lead to sea level rise, he said. “It is really important to understand how the Greenland Ice Sheet flows, slides and melts today, in order to be able to predict how it will contribute to sea level rise in the future.”

To investigate the impact of crevasses on ice sheet flow, the team first analyzed crevasse extent at Sermeq Avannarleq, northeast of Ilulissat, West Greenland. The scientists detected crevasses in high-resolution digital images taken in 1985 and 2009 and what they found surprised them. “We initially weren't looking for changes in crevasse area, we had thought it was stationary in time,” Colgan said. “But we found that the change in crevasse area was significant.”

Several factors influence the extent of crevasses, Colgan said. The weight of ice surrounding the crevasse acts as a “closing” force on crevasses whereas tensile stress, caused by local variations in surface slope, acts as an “opening” force. Warmer temperatures, however, result in increased surface melt and a thinning ice sheet reducing the closing force. Conversely, the subsequent change in ice flow speed steepens the ice sheet, which strengthens the tensile stress. As the ice sheet melts, a third factor also contributes to the crevasses expanding, Colgan said. “Twenty years ago crevasses might have been sitting open exposed to air, but now they are filled with water which forces them open.”

The team then went on to investigate how the crevasse area increase might impact ice sheet sliding. In this study, and a companion study published online September 13 in the Journal of Glaciology, the scientists compared the drainage of water by crevasses and moulins—near-vertical chutes in the ice—and found moulin drainage to be more efficient in moving water to the bed of the ice sheet and promoting sliding. But with the increase in crevasse area, the number of moulins had decreased, Colgan said. “The crevasse fields seem to be absorbing the moulins.”

Previously, scientists had believed that as more ice melts and water accumulates on the surface of the ice sheet, more water drains though the moulin network to the underside of the ice sheet enhancing its slide into the ocean. “For the last ten years popular opinion has been more melt equals more slide into the ocean,” he said. “Some recent papers have speculated that more melt might equal no change in sliding, but ours might be the first paper that says that despite more melt, changes in the way that the water is routed to the bed might equal less slide.”

The team now intends to investigate whether crevasse area has increased Greenland-wide and, if so, determine the impact on ice-sheet sliding. While the study may have identified one previously unrecognized influence on ice-sheet dynamics, Colgan cautions it is just one of many factors which determine the iceberg calving rate. “The recent trend of increasing iceberg calving rates is unlikely to be reversed by a potential decrease in sliding, as the majority of ice movement comes from flow rather than sliding,” he said.

The study “An increase in crevasse extent, West Greenland: Hydrologic implications” was funded by the National Aeronautics and Space Administration and the National Science Foundation. Coauthors include CIRES Director Konrad Steffen, CIRES student W. Scott McLamb and CIRES Fellow Waleed Abdalati. Collaborators on the project include the Aerospace Engineering and Sciences and Civil, Environmental, and Architectural Engineering departments at the University of Colorado Boulder, the Institute of Arctic and Alpine Research at the University of Colorado Boulder and the Geophysical Institute of the University of Alaska Fairbanks.

CIRES graduate student, Daniel McGrath led the study published in the Journal of Glaciology “Assessing the summer water budget of a moulin basin in the Sermeq Avannarleq ablation region, Greenland Ice Sheet.” Coauthors of this study include William Colgan and Konrad Steffen. Collaborators on the project include the Aerospace Engineering Sciences Department at the University of Colorado Boulder and the Extreme Ice Survey, Boulder.

William Colgan, CIRES, 303-735-3681, william.colgan@colorado.edu

Konrad Steffen, CIRES, 303-492-8773, konrad.steffen@colorado.edu

Karin Vergoth, CIRES, 303-497-5125, karin.vergoth@colorado.edu


The black smoke that rose from the water’s surface during controlled burns of surface oil from the Deepwater Horizon oil spill last year pumped more than one million pounds of black carbon (soot) pollution into the atmosphere, according to a new study published online this week by researchers at Cooperative Institute for Research in Environmental Sciences (CIRES) and NOAA.

This amount is roughly equal to the total black carbon emissions normally released by all ships that travel the entire Gulf of Mexico during a 9-week period, scientists noted.

Black carbon, whose primary component is often called soot, is known to degrade air quality and contribute to warming of the Earth’s atmosphere. The new study, published online this week in Geophysical Research Letters, provides some of the most detailed observations made of black carbon sent airborne by burning surface oil.

“Scientists have wanted to know more about how much black carbon pollution comes from controlled burning and the physical and chemical properties of that pollution. Now we know a lot more,” said lead author Anne Perring, a scientist with CIRES and the Chemical Sciences Division of NOAA’s Earth System Research Laboratory (ESRL) in Boulder, Colo.

During the 2010 Gulf oil spill, an estimated one of every 20 barrels of spilled oil was deliberately burned off to reduce the size of surface oil slicks and minimize impacts of oil on sensitive shoreline ecosystems and marine life. In response to the spill, NOAA quickly redirected its WP-3D research aircraft to survey the atmosphere above the spill site in June. During a flight through one of the black plumes, scientists used sophisticated instrumentation on board to characterize individual black carbon particles. NOAA’s single particle soot photometer was key to making the black carbon measurements.

Black carbon is the most light-absorbing airborne particle in the atmosphere and the reason for the black color in the smoky plumes that rise from the surface oil fires. Black carbon can also cause warming of the atmosphere by absorbing light. Prolonged exposure to breathing black carbon particles from human and natural burning sources is known to cause human health effects.

During the 9 weeks active surface oil burning, an total of 1.4 to 4.6 million pounds (0.63 to 2.07 million kilograms) of black carbon was sent into the atmosphere of the Gulf of Mexico, the study estimated.

The study also found that the hot soot plumes from the controlled burns reached much higher into the atmosphere than ship emissions normally rise, potentially prolonging the amount of time the black carbon can remain in the atmosphere which would affect where the black carbon end up.

The researchers also found that the average size of the black carbon particles was much larger than that emitted from other sources in the Gulf region, and that the emitted particles produced were almost all black carbon, unlike other sources such as forest fires that tend to produce other particles along with black carbon.

“The size and makeup of the black carbon particles determine how fast the particles are removed from the atmosphere by various processes, which ultimately affects their impact on climate,” says Perring. Larger particles are removed from the atmosphere more quickly and thus have smaller climate impacts. And, those same properties of black carbon are important for assessing human health impacts.

Finally, Perring and her colleagues found that of the oil that was burned, 4 percent of the mass was released as black carbon, an important metric rarely observed during cleanup of an oceanic oil spill, which could help guide future decision-making.

The new paper, Characteristics of Black Carbon Aerosol from a Surface Oil Burn During the Deepwater Horizon Oil Spill, has 15 co-authors from NOAA ESRL and CIRES and can be found on the the Geophysical Research Letter website.

Contacts:

Anne Perring, CIRES, 303-497-5337Anne.Perring@noaa.gov

Karin Vergoth, CIRES, 303-497-5125, karin.vergoth@colorado.edu