NOAA study: Increase in particles high in Earth’s atmosphere has offset some recent climate warming

July 21, 2011

Light from a lidar instrument forms a beam in the sky over Boulder, Colo.. NOAA researchers and colleagues used lidar data to better understand recent changes in the amounts of tiny particles high in Earth's atmosphere.

Download here. (Credit: CIRES/NOAA)

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 NOAA and published today 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 warmingeffect from the carbon dioxide increase during that same period.”

Sources of aerosols reach the stratosphere from above and below, as shown in the graph. Sulfur dioxide (SO2), carbonyl sulfide (OCS), and dimethyl sulfide(DMS) are the dominant surface emissions which contribute to aerosol formation.

Download here. (Credit: NOAA)

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 the University of Colorado and the Cooperative Institute for Research in Environmental Sciences (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, the University of Colorado, 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 co-author 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.

Lidar instruments - pointing up from the ground or down from satellites - use reflected light to measure the amounts of particles and their locations, which can influence climate.

Download here. (Credit: CIRES/NOAA)

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, University of Colorado; John Daniel, Chemical Sciences Division of NOAA’s Earth System Research Laboratory; Ryan Neely, CIRES-University of Colorado 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.

NOAA study: Slowing climate change by targeting gases other than carbon dioxide

August 3, 2011

The direct warming influence of all long-lived greenhouse gases in the atmosphere today attributable to human activities. CO_2's warming influence of 1.7 watts/m2 is equivalent to the heat from nearly 9 trillion 100-watt incandescent light bulbs placed across Earth's surface. The combined influence of the non-CO₂ greenhouse gases is equivalent to the heat from about 5 trillion bulbs. The category '"ther" includes a few very long-lived chemicals that can exert a climate influence for millennia. (Credit: NOAA)

Carbon dioxide remains the undisputed king of recent climate change, but other greenhouse gases measurably contribute to the problem. A new study, conducted by NOAA scientists and published online today 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 NOAA scientists  - Stephen Montzka, Ed Dlugokencky and James Butler of NOAA's Earth System Research Laboratory in Boulder, Colo. - 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. Therefore cutting emissions would quickly reduce their direct radiative forcing - a measure of warming influence.

"We know that recent 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," Montzka said. "But lowering emissions of greenhouse gases other than carbon dioxide could lead to some rapid changes for the better."

The direct radiative forcing (warming effect) of greenhouse gases under various scenarios. a) Red: constant 2008 emissions of both CO₂ and non-CO₂ greenhouse gases. b) An 80% cut in non-CO₂ emissions. c) An 80% cut in CO₂ emissions. d) An 80% cut in all greenhouse gas emissions. In all scenarios, emissions cuts are phased in between 2009 and 2050. (Credit: NOAA)

Scientists know that stabilizing the warming effect of CO₂ in the atmosphere would require a decrease of about 80 percent in human-caused 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 to this extent could result in a decrease in the total warming effect from these 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."

Global temperatures were seventh warmest on record for July

August 15, 2011

 Global surface temperature Anomalies - July 2011.  (Credit: NOAA)

The globe experienced its seventh warmest July since record keeping began in 1880. July's Arctic sea ice extent was the smallest on record for that month since records began in 1979.

The monthly analysis from NOAA's National Climatic Data Center is part of the suite of climate services NOAA provides government, business and community leaders so they can make informed decisions.

Global Temperature Highlights: July

• The combined global land and ocean average surface temperature for July 2011 was the seventh warmest on record for that month at 61.43 F (16.37 C), which is 1.03 F (0.57 C) above the 20th century average of 60.4 F (15.8 C). The margin of error associated with this temperature is +/- 0.16 F (0.09 C).
  
  
• Separately, the global land surface temperature for July was 1.51 F (0.84 C) above the 20th century average of 57.8 F (14.3 C), making it the fifth warmest July on record. The margin of error is +/- 0.23 F (0.13 C). Warmer-than-average conditions occurred across Northern Europe, western and eastern Russia, and most of North America. Cooler-than-average regions included central Russia, Western Europe, much of the western United States, and southwestern Canada.
  
  
• The July global ocean surface temperature was 0.85 F (0.47 C) above the 20th century average of 61.5 F (16.4 C), making it the 11th warmest July on record. The margin of error is +/- 0.07 F (0.04 C). The warmth was most pronounced across Baffin Bay and the Labrador Sea in the Northern Hemisphere high latitudes and in the north central and northwestern Pacific Ocean.
  

• July 2011 temperatures were above normal for all states and territories in Australia for the first month since April 2010. La Nina conditions during 2010/11 kept temperatures below normal across most of the country for more than a year.
  
  
• The United Kingdom average monthly July temperature of 57.4 F (14.1 C) was the coolest July temperature since 2000 at 0.9 F (0.5 C) below the long-term average, which dates to 1910.The average minimum July temperature was the coolest for this month since 1980. Dublin Airport reported its coolest July in 46 years, with an average temperature of 56.8 F (13.8 C).

Global Temperature Highlights: Year to date

• The combined global land and ocean average surface temperature for the January - July period was 0.92 F (0.51 C) above the 20th century average of 56.9 F (13.8 C), making it the 11th warmest such period on record. The margin of error is +/- 0.16 F (0.09 C).
  
  
• The January   - July worldwide land surface temperature was 1.40 F (0.78 C) above the 20th century average - the eighth warmest such period on record. The margin of error is +/- 0.36 F (0.20 C). Warmer-than-average conditions were prevalent across most of Russia, the Middle East, northern Africa, Europe, the southern United States, and Mexico. Cooler-than-average regions prevailed over the northwestern United States, southwestern Canada, and most of Australia.
  
  
• The global ocean surface temperature for the year to date was 0.74 F (0.41 C) above the 20th century average and was the 11th warmest such period on record. The margin of error is +/-0.07 F (0.04 C). The warmth was most pronounced across the Labrador Sea, most of the central and western Pacific, the equatorial Atlantic, and much of the mid-latitude southern oceans.
  
  
• Neither El Nino nor La Ni�a conditions were present during July 2011. According to NOAA's Climate Prediction Center, ENSO neutral conditions are expected to continue into the Northern Hemisphere fall 2011, with an equally likely chance of ENSO-neutral or La Ni�a conditions thereafter.

Polar Sea Ice and Precipitation Highlights

• The average Arctic sea ice extent during July was 21.6 percent below average, ranking as the smallest July extent since satellite records began in 1979. The extent was 81,000 square miles (210,000 square kilometers) below the previous July record low, set in 2007.
  
  
• The July 2011 Antarctic sea ice extent was 0.54 percent below average and was the 12th smallest July extent since records began in 1979.

• Seoul, South Korea received more than 11.8 inches (300 millimeters) of precipitation on July 27, the heaviest single-day rainfall in the city since 1907.

http://www.noaanews.noaa.gov/stories2011/20110815_globalstats.html

Awsome High Res Pic Of Saturn   (Cassini Space Craft)

U.S. experiences second warmest summer on record

Texas has warmest summer on record of any state

September 8, 2011

The blistering heat experienced by the nation during August, as well as the June through August months, marks the second warmest summer on record according to scientists at NOAA’s National Climatic Data Center (NCDC) in Asheville, N.C. The persistent heat, combined with below-average precipitation across the southern U.S. during August and the three summer months, continued a record-breaking drought across the region.

The average U.S. temperature in August was 75.7 degrees F, which is 3.0 degrees above the long-term (1901-2000) average, while the summertime temperature was 74.5 degrees F, which is 2.4 degrees above average. The warmest August on record for the contiguous United States was 75.8 degrees F in 1983, while its warmest summer on record at 74.6 degrees F occurred in 1936. Precipitation across the nation during August averaged 2.31 inches, 0.29 inches below the long-term average. The nationwide summer precipitation was 1.0 inch below average.

This monthly analysis, based on records dating back to 1895, is part of the suite of climate services NOAA provides.

• Excessive heat in six states – Arizona, Colorado, New Mexico, Texas, Oklahoma, and Louisiana – resulted in their warmest August on record. This year ranked in the top ten warmest August for five other states: Florida (3rd), Georgia (4th), Utah (5th), Wyoming (8th), and South Carolina (9th).The Southwest and South also had their warmest August on record.

• Only nine of the lower 48 states experienced August temperatures near average, and no state had August average temperatures below average.

• Wetter-than-normal conditions were widespread across the Northeastern United States, which had its second wettest August, as well as parts of the Northern Plains and California.  Drier-than-normal conditions reigned across the interior West, the Midwest, and the South.

• Hurricane Irene made landfall near Cape Lookout, N.C. as a Category 1 storm on August 27, marking the first hurricane landfall in the U.S. since Hurricane Ike in September 2008. Irene made a second landfall in New Jersey as a hurricane on August 28, marking only the second recorded hurricane landfall in that state.

• Irene contributed to New Jersey, New York, Vermont, and New Hampshire having their wettest August on record. Meanwhile, Massachusetts (2nd), Connecticut (2nd), Delaware (3rd), Maine (3rd), Maryland (5th), Pennsylvania (5th), and Rhode Island (9th) had a top 10 wet August.

• Several major U.S. cities broke all-time monthly rainfall amounts during August. New York City (Central Park) measured 18.95 inches of rain, exceeding the previous record of 16.85 inches in 1882. In Philadelphia, 19.31 inches of rain was observed, besting the previous monthly record of 13.07 inches in September 1999.

• Louisiana (3rd), Tennessee (4th), Texas (5th), Mississippi (6th), Georgia, (6th), Illinois (8th), Washington (9th), and Alabama (9th) had precipitation totals among their top ten driest on record.

• Despite record rainfall in parts of the country, drought covered about one-third of the contiguous United States, according to the U.S. Drought Monitor. The Palmer Hydrologic Drought Index indicated that parts of Louisiana, New Mexico, Oklahoma and Texas are experiencing drought of greater intensity, but not yet duration, than those of the 1930s and 1950s. Drought intensity refers to the rate at which surface and ground water is lost, due to a combination of several factors, including evaporation and lack of precipitation.

• An analysis of Texas statewide tree-ring records dating back to 1550 indicates that the summer 2011 drought in Texas is matched by only one summer (1789), indicating that the summer 2011 drought appears to be unusual even in the context of the multi-century tree-ring record.

   

• Texas, Oklahoma, New Mexico, and Louisiana had their warmest (June-August) summers on record. Average summer temperatures in Texas and Oklahoma, at 86.8 degrees F and 86.5 degrees F, respectively, exceeded the previous seasonal statewide average temperature record for any state during any season. The previous warmest summer statewide average temperature was in Oklahoma, during 1934 at 85.2 degrees F.

• Fifteen states had a summer average temperature ranking among their top ten warmest. West of the Rockies, a persistent trough brought below-average temperatures to the Pacific Northwest, where Washington and Oregon were the only states across the lower 48 to have below-average summer temperatures.

• Texas had its driest summer on record, with a statewide average of 2.44 inches of rain. This is 5.29 inches below the long-term average, and 1.04 inches less than the previous driest summer in 1956. New Mexico had its second driest summer and Oklahoma its third driest summer. New Jersey and California had their wettest summers on record with 22.50 inches and 1.93 inches, respectively.

• The U.S. Climate Extremes Index, a measure of the percent area of the country experiencing extreme climate conditions, was nearly four times the average value was during summer 2011. This is the third largest summer value of the record, which dates to 1910. The major drivers were extremes in warm minimum and maximum temperatures and in the wet and dry tails of the Palmer Drought Severity Index.

• Based on NOAA's Residential Energy Demand Temperature Index, the contiguous U.S. temperature-related energy demand was 22.3 percent above average during summer. This is the largest such value during the index’s period of record, which dates to 1895.

Other U.S. climate highlights

• During the six-month period (March-August), much-above-average temperatures dominated the southern and eastern United States. New Mexico, Oklahoma, Texas, Louisiana, South Carolina, and Florida, all experienced their warmest March-August on record. Cooler-than-average temperatures dominated the West and Northwest.

• For the year-to-date period, the average statewide temperature for Texas was 69.9 degrees F, the warmest such period on record for the state. This bests the previous record for the year-to-date period of 69.8 degrees F in 2000.

• For precipitation year-to-date, New Mexico, Texas, and Louisiana have all had their driest January-August periods on record, while Ohio, Pennsylvania, New York, New Jersey, and Connecticut were record wet during the same period.

http://www.noaanews.noaa.gov/stories2011/20110908_auguststats.html

U.S. dealt another La Nina winter but 'wild card' could trump it

Devastating drought in Southern Plains likely to continue

October 20, 2011

The Southern Plains should prepare for continued drier and warmer than average weather, while the Pacific Northwest is likely to be colder and wetter than average from December through February, according to the annual Winter Outlook released today by NOAA.

For the second winter in a row, La Nina will influence weather patterns across the country, but as usual, it’s not the only climate factor at play. The 'wild card' is the lesser-known and less predictable Arctic Oscillation that could produce dramatic short-term swings in temperatures this winter.

NOAA expects La Nina, which returned in August, to gradually strengthen and continue through the upcoming winter. It is associated with cooler than normal water temperatures in the tropical Pacific Ocean and influences weather throughout the world.

 "The evolving La Nina will shape this winter," said Mike Halpert, deputy director of NOAA's Climate Prediction Center. "There is a wild card, though. The erratic Arctic Oscillation can generate strong shifts in the climate patterns that could overwhelm or amplify La Nina's typical impacts."

The Arctic Oscillation is always present and fluctuates between positive and negative phases. The negative phase of the Arctic Oscillation pushes cold air into the U.S. from Canada. The Arctic Oscillation went strongly negative at times the last two winters, causing outbreaks of cold and snowy conditions in the U.S. such as the “Snowmaggedon” storm of 2009.  Strong Arctic Oscillation episodes typically last a few weeks and are difficult to predict more than one to two weeks in advance.

With La Nina in place Texas, Oklahoma, New Mexico and parts of surrounding states are unlikely to get enough rain to alleviate the ongoing drought. Texas, the epicenter of the drought, experienced its driest 12-month period on record from October 2010 through September 2011.

Stormy periods can occur anytime during the winter season. To improve the ability to predict and track winter storms, NOAA implemented a more accurate weather forecast model on Oct.18.  Data gathered from the model will support local weather forecast office efforts to prepare for and protect the public from weather events. This service is helping the country to become a Weather-Ready Nation at a time when extreme weather is on the rise.

According to the U.S. Winter Outlook (December through February) odds tilt in favor of:

• Pacific Northwest:  colder and wetter than average. La Nina often results in below-average temperatures and increased mountain snow in the Pacific Northwest and western Montana during the winter months. This may set the stage for spring flooding in the Missouri River Basin;
  
• California: colder than average and wetter than average conditions in northern California and drier than average conditions in southern California.  All of the southern part of the nation are at risk of having above normal wildfire conditions starting this winter and lasting into the spring;
• Northern Plains: colder and wetter than average.  Spring flooding could be a concern in parts of this region;
• Southern Plains and Gulf Coast States: warmer and drier than average. This will likely exacerbate drought conditions in these regions;
• Florida and south Atlantic Coast: drier than average, with an equal chance for above-, near-, or below-normal temperatures. Above normal wildfire conditions;
• Ohio and Tennessee Valleys: wetter than average with equal chances for above-, near-, or below-average temperatures. Potential for increased storminess and flooding;
• Northeast and Mid-Atlantic: equal chances for above-, near-, or below-normal temperatures and precipitation. Winter weather for these regions is often driven not by La Nina but by the Arctic Oscillation. If enough cold air and moisture are in place, areas north of the Ohio Valley and into the Northeast could see above-average snow;
• Great Lakes: colder and wetter than average;
• Hawaii: above-average temperatures in the western islands with above normal precipitation during the winter.  Some drought recovery is expected across the state with Kauai and Oahu having the best potential for full recovery.
• Alaska: colder than average over the southern half of the state and the panhandle with below average precipitation in the interior eastern part of the state.

http://www.noaanews.noaa.gov/stories2011/20111020_winteroutlook.html

NOAA greenhouse gas index continues climbing

November 9, 2011

NOAA�s updated Annual Greenhouse Gas Index (AGGI), which measures the direct climate influence of many greenhouse gases such as carbon dioxide and methane, shows a continued steady upward trend that began with the Industrial Revolution of the 1880s.

Started in 2004, the AGGI reached 1.29 in 2010. That means the combined heating effect of long-lived greenhouse gases added to the atmosphere by human activities has increased by 29 percent since 1990, the �index� year used as a baseline for comparison. This is slightly higher than the 2009 AGGI, which was 1.27, when the combined heating effect of those additional greenhouse gases was 27 percent higher than in 1990.

�The increasing amounts of long-lived greenhouse gases in our atmosphere indicate that climate change is an issue society will be dealing with for a long time,� said Jim Butler, director of the Global Monitoring Division of NOAA�s Earth System Research Laboratory in Boulder, Colo. �Climate warming has the potential to affect most aspects of society, including water supplies, agriculture, ecosystems and economies. NOAA will continue to monitor these gases into the future to further understand the impacts on our planet.�

The AGGI is analogous to the dial on an electric blanket � that dial does not tell you exactly how hot you will get, nor does the AGGI predict a specific temperature. Yet just as turning the dial up increases the heat of an electric blanket, a rise in the AGGI means greater greenhouse warming.

NOAA scientists created the AGGI recognizing that carbon dioxide is not the only greenhouse gas affecting the balance of heat in the atmosphere. Many other long-lived gases also contribute to warming, although not currently as much as carbon dioxide.

The AGGI includes methane and nitrous oxide, for example, greenhouse gases that are emitted by human activities and also have natural sources and sinks. It also includes several chemicals known to deplete Earth�s protective ozone layer, which are also active as greenhouse gases. The 2010 AGGI reflects several changes in the concentration of these gases, including:

• A continued steady increase in carbon dioxide: Global carbon dioxide levels rose to an average of 389 parts per million in 2010, compared with 386 ppm in 2009, and 354 in the index or comparison year of 1990. Before the Industrial Revolution of the 1880s, carbon dioxide concentration in the atmosphere was about 280 ppm. Carbon dioxide levels swing up and down in natural seasonal cycles, but human activities � primarily the burning of coal, oil, and gas for transportation and power � have driven a consistent upward trend in concentration. 
• A continued recent increase in methane: Methane levels rose in 2010 for the fourth consecutive year after remaining nearly constant for the preceding 10 years, up to 1799 parts per billion. Methane measured 1794 ppb in 2009, and 1714 ppb in 1990. Pound for pound, methane is 25 times more potent as a greenhouse gas than carbon dioxide, but there�s less of it in the atmosphere.

• A continued steady increase in nitrous oxide: Best known as laughing gas in dentistry, nitrous oxide is also a greenhouse gas emitted from natural sources and as a byproduct of agricultural fertilization, livestock manure, sewage treatment and some industrial processes.
• A continued recent drop in two chlorofluorocarbons, CFC11 and CFC12: Levels of these two compounds � which are ozone-depleting chemicals in addition to greenhouse gases � have been dropping at about one percent per year since the late 1990s, because of an international agreement, the Montreal Protocol, to protect the ozone layer.

Scientists at NOAA�s Earth System Research Laboratory prepare the AGGI each year from atmospheric data collected through an international cooperative air sampling network of more than 100 sites around the world.

The 2011 Arctic Report Card, compiled by scientists from 14 countries, "shows that record-setting changes are occurring throughout the Arctic environmental system.

"Given the projection of continued global warming, it is very likely that major Arctic changes will continue in years to come, with increasing climatic, biological and social impacts," the report said.

The authors of the annual report -- first released in 2006 -- said there is now sufficient data to indicate a "persistent decline in the thickness and summer extent of the sea ice cover, and a warmer, fresher upper ocean."

Average temperatures over much of the Arctic have risen some 2.5 degrees F (1.5 degrees C) from a 1981-2010 baseline, and the minimum area of sea ice recorded this year, in September 2011, was the second lowest since 1979.

The "profound and continuing" changes have had an uneven impact on Arctic wildlife, threatening the icy habitats of polar bears and walruses but giving whales greater access to northern feeding areas, the report said.

The warming has also caused new vegetation to sprout in many areas, and has led to a 20 percent increase in phytoplankton, microscopic organisms that are the basis of the oceanic food chain.

The report also found that changes in Arctic winter wind patterns first detected in 2010 have continued.

"The Arctic region continues to warm, with less sea ice and greater green vegetation," said Monica Medina, of the US National Oceanic and Atmospheric Administration (NOAA).

NOAA-led study: Colorado oil and gas wells emit more pollutants than expected

Feb. 27, 2012  Contact: Katy Human, 303-497-4747

 

When NOAA scientists began routinely monitoring the atmosphere's composition at a tower north of Denver a few years ago, their instruments immediately sniffed something strange: plumes of air rich with chemical pollutants including the potent greenhouse gas methane.

Some of the pollutants picked up are known to damage air quality. Another, methane, is 25 times more effective per molecule than carbon dioxide at trapping heat in the atmosphere. The scientists were concerned. None of NOAA's other air composition monitoring towers - there are eight, in total, scattered around the continental United States - had recorded anything similar.

 

"So we set out to figure out where these chemicals were coming from, by going from the tower measurements 1,000 feet high up, down to the ground in a mobile laboratory," said Gabrielle Petron, Ph.D., an atmospheric scientist with NOAA's Earth System Research Laboratory (ESRL) and the Cooperative Institute for Research in Environmental Sciences (CIRES).

Petron and co-workers customized

In 2008, the year most of the data were collected, Weld County had nearly 14,000 operating oil and gas wells.

The research team's chemical fingerprinting work showed that oil and gas equipment and activities - well pads equipment including condensate storage tanks, pipelines, compressors and more - leaked or vented an estimated 4 percent of all natural gas produced to the atmosphere. That loss is about double the previous best-guess estimate, based on engineering calculations and industry data, of about 2 percent loss.

"We may have been significantly underestimating methane emissions by this industry in this region," Petron said.

The team also found that emissions of benzene, a known carcinogen, are underestimated. Benzene is tracked and regulated by the Environmental Protection Agency (EPA).

Petron and her colleagues found evidence of at least two sources of benzene in the region: oil and gas operations and something else, most likely cars and trucks on roads. And the new study found benzene emissions from oil and gas operations in the region to be significantly higher than expected, between 385 and 2,055 metric tons in 2008, compared with earlier estimates ranging from about 60 to 145 per year.

Finally, the researchers' findings suggest that oil and gas-related emissions of more reactive volatile organic compounds, which contribute to lung-damaging ozone pollution, are also underestimated. More reactive VOCs were not directly measured in the 2008 study, but are almost certainly co-emitted with methane and larger alkanes. According to the EPA, the northern Front Range has been out of compliance with federal health-based standards in the summer since 2007.

Chemist Greg Frost, Ph.D. also with NOAA and CIRES and a co-author of the new study, said the work demonstrates the value of studying emissions from several perspectives. Top-down studies (such as from the tall tower) can complement and verify bottom-up approaches (such as estimates based on average leak rates at pipe junctions).

"What Gabrielle has done is to use the mobile laboratory and tower data to make top-down estimates of emissions, which can be used to evaluate the bottom-up estimates from industry and regulatory agencies," Frost said. "This is going to inspire a lot more research."