Posts tagged NCAR
Volcanic aerosols, not pollutants, tamped down recent Earth warming, says CU study
0March 1, 2013
A team led by the University of Colorado Boulder looking for clues about why Earth did not warm as much as scientists expected between 2000 and 2010 now thinks the culprits are hiding in plain sight — dozens of volcanoes spewing sulfur dioxide.
The study results essentially exonerate Asia, including India and China, two countries that are estimated to have increased their industrial sulfur dioxide emissions by about 60 percent from 2000 to 2010 through coal burning, said lead study author Ryan Neely, who led the research as part of his CU-Boulder doctoral thesis. Small amounts of sulfur dioxide emissions from Earth’s surface eventually rise 12 to 20 miles into the stratospheric aerosol layer of the atmosphere, where chemical reactions create sulfuric acid and water particles that reflect sunlight back to space, cooling the planet.
Neely said previous observations suggest that increases in stratospheric aerosols since 2000 have counterbalanced as much as 25 percent of the warming scientists blame on human greenhouse gas emissions. “This new study indicates it is emissions from small to moderate volcanoes that have been slowing the warming of the planet,” said Neely, a researcher at the Cooperative Institute for Research in Environmental Sciences, a joint venture of CU-Boulder and the National Oceanic and Atmospheric Administration.
A paper on the subject was published online in Geophysical Research Letters, a publication of the American Geophysical Union. Co-authors include Professors Brian Toon and Jeffrey Thayer from CU-Boulder; Susan Solomon, a former NOAA scientist now at the Massachusetts Institute of Technology; Jean Paul Vernier from NASA’s Langley Research Center in Hampton, Va.; Catherine Alvarez, Karen Rosenlof and John Daniel from NOAA; and Jason English, Michael Mills and Charles Bardeen from the National Center for Atmospheric Research in Boulder.
The new project was undertaken in part to resolve conflicting results of two recent studies on the origins of the sulfur dioxide in the stratosphere, including a 2009 study led by the late David Hoffman of NOAA indicating aerosol increases in the stratosphere may have come from rising emissions of sulfur dioxide from India and China. In contrast, a 2011 study led by Vernier — who also provided essential observation data for the new GRL study — showed moderate volcanic eruptions play a role in increasing particulates in the stratosphere, Neely said.
The new GRL study also builds on a 2011 study led by Solomon showing stratospheric aerosols offset about a quarter of the greenhouse effect warming on Earth during the past decade, said Neely, also a postdoctoral fellow in NCAR’s Advanced Study Program.
The new study relies on long-term measurements of changes in the stratospheric aerosol layer’s “optical depth,” which is a measure of transparency, said Neely. Since 2000, the optical depth in the stratospheric aerosol layer has increased by about 4 to 7 percent, meaning it is slightly more opaque now than in previous years.
“The biggest implication here is that scientists need to pay more attention to small and moderate volcanic eruptions when trying to understand changes in Earth’s climate,” said Toon of CU-Boulder’s Department of Atmospheric and Oceanic Sciences. “But overall these eruptions are not going to counter the greenhouse effect. Emissions of volcanic gases go up and down, helping to cool or heat the planet, while greenhouse gas emissions from human activity just continue to go up.”
The key to the new results was the combined use of two sophisticated computer models, including the Whole Atmosphere Community Climate Model, or WACCM, Version 3, developed by NCAR and which is widely used around the world by scientists to study the atmosphere. The team coupled WACCM with a second model, the Community Aerosol and Radiation Model for Atmosphere, or CARMA, which allows researchers to calculate properties of specific aerosols and which has been under development by a team led by Toon for the past several decades.
Neely said the team used the Janus supercomputer on campus to conduct seven computer “runs,” each simulating 10 years of atmospheric activity tied to both coal-burning activities in Asia and to emissions by volcanoes around the world. Each run took about a week of computer time using 192 processors, allowing the team to separate coal-burning pollution in Asia from aerosol contributions from moderate, global volcanic eruptions. The project would have taken a single computer processor roughly 25 years to complete, said Neely.
The scientists said 10-year climate data sets like the one gathered for the new study are not long enough to determine climate change trends. “This paper addresses a question of immediate relevance to our understanding of the human impact on climate,” said Neely. “It should interest those examining the sources of decadal climate variability, the global impact of local pollution and the role of volcanoes.”
While small and moderate volcanoes mask some of the human-caused warming of the planet, larger volcanoes can have a much bigger effect, said Toon. When Mount Pinatubo in the Philippines erupted in 1991, it emitted millions of tons of sulfur dioxide into the atmosphere that cooled the Earth slightly for the next several years.
The research for the new study was funded in part through a NOAA/ ESRL-CIRES Graduate Fellowship to Neely. The National Science Foundation and NASA also provided funding for the research project. The Janus supercomputer is supported by NSF and CU-Boulder and is a joint effort of CU-Boulder, CU Denver and NCAR.
Related posts:
Boulder Open Space and Mountain Parks begins seasonal cliff-nesting raptor closures
0January 30, 2013
Each year, the City of Boulder Open Space and Mountain Parks (OSMP) Department temporarily closes areas to the public in order to protect nesting and roosting raptors. The following areas and formations will be closed from Feb. 1 through July 31:
- Lefthand Canyon Palisades, at the intersection of Lefthand Canyon Drive and Olde Stage Road (Buckingham picnic area remains open);
- Mount Sanitas, First Buttress, accessible from the Mount Sanitas trailhead, a half mile west of Fourth Street and Mapleton Avenue (no closures to the bouldering areas along the ridge; Mount Sanitas trail will remain open);
- Gregory Canyon Amphitheater, including the Amphitheater Express Trail and the 3rd Pinnacle (the Amphitheater Trail to Saddle Rock will remain open);
-
- Third Flatiron, including the East and West Ironing Boards, Queen Anne’s Head and Jaws, and WC Pinnacle, accessible from Chautauqua trailhead;
- Flagstaff Mountain: the north side of Flagstaff Mountain will be closed (the Boy Scout Trail will remain open);
- Skunk Canyon, including Ridges 2, 3 and 4, the Aechean Pronouncement, the Dreadnaught, the North Ridge and the entirety of Sacred Cliffs, accessible from NCAR trailhead at the west end of Table Mesa Road;
- The Back Porch and The Box, accessible from the NCAR trailhead at the west end of Table Mesa Road;
- Bear Creek Spire, accessible from the NCAR trailhead at the west end of Table Mesa Road;
- Fern Canyon, accessible from the NCAR trailhead at the west end of Table Mesa Road (the designated Fern Canyon hiking trail will remain open);
- Shadow Canyon and the Matron, accessible from the South Mesa Trailhead (the Maiden will remain open and accessible from the east; the designated Shadow Canyon hiking trail will re-open in 2013 following post-fire maintenance);
- The Sphinx, accessible from the NCAR trailhead at the west end of Table Mesa Road;
- Diamond Head and SoBo Buttress, west of Shadow Canyon, accessible from South Mesa Trailhead (South Boulder Peak Trail will remain open);
- The entire Mickey Mouse wall, accessible from the Goshawk Ridge Trail.
High-quality cliff habitat and rich food resources on OSMP lands, as well as community cooperation in protecting nesting sites, sustains the mountain backdrop as a regionally important area for nesting falcons and golden eagles. OSMP volunteers and staff have been monitoring raptor nesting and roosting areas since 1984, and the program is an integral part of efforts to protect the species and adaptively manage the closures.
Trespassing violations can result in a summons with penalties up to 90 days in jail and/or a $1,000 fine. OSMP relies heavily on the public to respect the closures, and the cooperation of visitors to these areas is greatly appreciated. Closures may be lifted early, if no raptor activity is observed at these sites.
Some modifications have occurred to the Flagstaff and The Sphinx raptor closures. Please visit Open Space and Mountain Parks’ website at www.osmp.org for detailed maps and up-to-date information on raptor closures or call 303-441-3440.
Related posts:
CU-Boulder wins $1.4 million NSF award for climate change, water sustainability study
0October 10, 2012
The University of Colorado at Boulder has been awarded $1.4 million for a new study on how changes in land use, forest management and climate may affect trans-basin water diversions in Colorado and other semi-arid regions in the western United States.
The grant, part of the National Science Foundation-U.S. Department of Agriculture Water Sustainability Climate Program, was awarded to Assistant Professor Noah Molotch of the geography department. Molotch and his team will be identifying thresholds, or “tipping points,” of change in land use, forest management and climate that may compromise the sustainability of the policies and procedures that dictate the timing and quality of water diverted from Colorado’s West Slope to the Front Range.
Molotch said that in Colorado and semi-arid regions around the world, trans-basin water diversions that redirect water from areas of surplus to areas of demand are based on policy agreements and infrastructure operations made under climatic and land use conditions that may differ considerably from conditions in the near future. Measurements over the past 50 years, for example, suggest a broad-scale reduction in snowpack water storage in the western U.S. because of regional warming temperatures, a trend due in part to a shift from snowfall to rainfall, he said.
The Colorado Big Thompson Project depends upon a dwindling supply of Western Slope snowpack.
In addition, land-cover changes associated with population growth, fire suppression and mountain pine beetle outbreaks have altered the hydrology of mid-mountain ecosystems in the West, said Molotch, who also is a scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. CU is teaming up with the National Center for Atmospheric Research in Boulder on the NSF-funded project.
The NSF award comes on the heels of a May 2012 agreement between water managers in Summit and Grand counties on Colorado’s West Slope and in the Denver area on how best to share water from the Colorado River basin. “This is a great example of communities that historically battled for water resources coming to the table in a good faith effort to find solutions to water allocation issues,” said Molotch. “These groups have no pretenses about the potential impacts of climate change and realize we can’t afford to bury our heads in the sand on this issue.”
Collaborators on the project include Patrick Bourgeron and Mark Williams, fellows at CU-Boulder’s Institute of Arctic and Alpine Research, and David Gochis, Kathleen Miller and David Yates of NCAR.
A study led by Molotch published Sept. 10 in Nature Geoscience tied forest “greenness” in the western United States to fluctuating year-to-year snowpack. The study indicated mid-elevation mountain ecosystems — where people increasing are building second homes and participating in a myriad of outdoor recreational activities — are most sensitive to rising temperatures and changes in precipitation and snowmelt.
“We found that mid-elevation forests show a dramatic sensitivity to snow that fell the previous winter in terms of accumulation and subsequent melt,” said Molotch, also a fellow at INSTAAR. “If snowpack declines, forests become more stressed, which can lead to ecological changes that include alterations in the distribution and abundance of plant and animal species as well as vulnerability to perturbations like fire and beetle kill.”
Colorado snowpack was at an all time low this past winter
As part of the new award, Molotch and his team will evaluate regional climate models in the mountain West developed at NCAR in an attempt to make temperature, precipitation and snowpack projections “more robust,” Molotch said. While the efficiency of water in trans-basin diversion projects in the western U.S. has in the past been enhanced by the natural storage of moisture in mountain snowpack that allowed for a slow, steady delivery of water into the system, warming temperatures are already causing this beneficial “drip effect” to be greatly reduced, he said.
If the winter temperatures are hovering around 15 degrees Fahrenheit and the climate warms by a few degrees, for example, there will be negligible impact on snowpack, Molotch said. But if temperatures hover near freezing, slight temperature increases can trigger earlier snowmelt, and precipitation that used to be in the form of snow turns to rain, significantly affecting trans-basin water diversion activities.
“One of the most interesting aspects of this project to me is the changes we are seeing in the ‘wildland-urban interface,’ particularly in Colorado,” he said. “There is some irony that Front Range people who have built second homes in Summit County, for example, may actually start to have an effect on the water they have relied on to be piped through the Continental Divide to the Denver area.”
Burned forests can cause early runoff
In addition to providing land and water resource decision makers with projections on how future water supply and demand will change in the future, the NSF-funded project will provide a unique educational experience for graduate students, Molotch said.
“We have climate change, snowpack, changes in land use, all feeding into the pipeline that is bringing water to Colorado’s Front Range,” he said. “As the two main stressors, climate change and land use increase, there is the possibility of pushing the systems into an unsustainable state.”
Related posts:
CU scientists discover a new threat from air pollution
0August 8, 2012
CU-led team discovers new atmospheric compound
tied to climate change and human health issues
An international research team led by the University of Colorado Boulder and the University of Helsinki has discovered a surprising new chemical compound in Earth’s atmosphere that reacts with sulfur dioxide to form sulfuric acid, which is known to have significant impacts on climate and health.
The new compound, a type of carbonyl oxide, is formed from the reaction of ozone with alkenes, which are a family of hydrocarbons with both natural and man-made sources, said Roy “Lee” Mauldin III, a research associate in CU-Boulder’s atmospheric and oceanic sciences department and lead study author. The study charts a previously unknown chemical pathway for the formation of sulfuric acid, which can result both in increased acid rain and cloud formation as well as negative respiratory effects on humans.
“We have discovered a new and important, atmospherically relevant oxidant,” said Mauldin. “Sulfuric acid plays an essential role in Earth’s atmosphere, from the ecological impacts of acid precipitation to the formation of new aerosol particles, which have significant climatic and health effects. Our findings demonstrate a newly observed connection between the biosphere and atmospheric chemistry.”
A paper on the subject is being published in the Aug. 9 issue of Nature.
Typically the formation of sulfuric acid in the atmosphere occurs via the reaction between the hydroxyl radical OH — which consists of a hydrogen atom and an oxygen atom with unpaired electrons that make it highly reactive — and sulfur dioxide, Mauldin said. The trigger for the reactions to produce sulfuric acid is sunlight, which acts as a “match” to ignite the chemical process, he said.
But Mauldin and his colleagues had suspicions that there were other processes at work when they began detecting sulfuric acid at night, particularly in forests in Finland — where much of the research took place — when the sun wasn’t present to catalyze the reaction. “There were a number of instances when we detected sulfuric acid and wondered where it was coming from,” he said.
In the laboratory, Mauldin and his colleagues combined ozone — which is ubiquitous in the atmosphere — with sulfur dioxide and various alkenes in a gas-analyzing instrument known as a mass spectrometer hooked up with a “flow tube” used to add gases. “Suddenly we saw huge amounts of sulfuric acid being formed,” he said.
Because the researchers wanted to be sure the hydroxyl radical OH was not reacting with the sulfur dioxide to make sulfuric acid, they added in an OH “scavenger” compound to remove any traces of it. Later, one of the research team members held up freshly broken tree branches to the flow tube, exposing hydrocarbons known as isoprene and alpha-pinene — types of alkenes commonly found in trees and which are responsible for the fresh pine tree scent.
“It was such a simple little test,” said Mauldin. “But the sulfuric acid levels went through the roof. It was something we knew that nobody had ever seen before.”
Mauldin said the new chemical pathway for sulfuric acid formation is of interest to climate change researchers because the vast majority of sulfur dioxide is produced by fossil fuel combustion at power plants. “With emissions of sulfur dioxide, the precursor of sulfuric acid, expected to rise globally in the future, this new pathway will affect the atmospheric sulfur cycle,” he said.
According to the U.S. Environmental Protection Agency, more than 90 percent of sulfur dioxide emissions are from fossil fuel combustion at power plants and other industrial facilities. Other sulfur sources include volcanoes and even ocean phytoplankton. It has long been known that when sulfur dioxide reacts with OH, it produces sulfuric acid that can form acid rain, shown to be harmful to terrestrial and aquatic life on Earth.
Airborne sulfuric acid particles — which form in a wide variety of sizes — play the main role in the formation of clouds, which can have a cooling effect on the atmosphere, he said. Smaller particles near the planet’s surface have been shown to cause respiratory problems in humans.
Mauldin said the newly discovered oxidant might help explain recent studies that have shown large parts of the southeastern United States might have cooled slightly over the past century. Particulates from sulfuric acid over the forests there may be forming more clouds than normal, cooling the region by reflecting sunlight back to space.
Most of the laboratory experiments for the study were conducted at the Leibniz-Institute for Tropospheric Research in Leipzig, Germany.
Co-authors on the study include Torsten Berndt and Frank Stratmann from the Leibniz-Institute for Tropospheric Research; Mikko Sipilä, Pauli Paasonen, Tuukka Petäjä, Theo Kurtén, Veli-Matti Kerminen and Markku Kulmula from the University of Helsinki in Finland; and Saewung Kim from the National Center for Atmospheric Research in Boulder. Mauldin also is affiliated with NCAR and the University of Helsinki.
The study was funded by the European Commission Sixth Framework program, the Academy of Finland, The Finnish Center of Excellence, the European Research Council, the Kone Foundation, the Väisälä Foundation, the Maj and Tor Nessling Foundation, the Otto Malm Foundation and the U.S. National Science Foundation.
Related posts:
Boulder Fire Outbreak from lightning: Evacuations Flagstaff
0June 26, 2012
The latest on the spate of lighting cause fire here in the city of Boulder from the office of emergency management:
June 26, 4:45 p.m. – Pre-evacuation notices go to city residents
Pre-evacuation notices went out to 931 City of Boulder phone numbers. The area that received calls is bordered by Dartmouth on the north, Broadway on the east, all the way to the south edge of town. People should be ready to evacuate quickly. A Type 1 Federal Incident team is on its way.
June 26 – 4:19 p.m. – All Open Space properties are closed from Eldo. Springs to Boulder Canyon
All open space and recreational areas from Eldorado Springs to Boulder Canyon are closed until further notice.
June 26 – 4 p.m.
NCAR is voluntarily evacuating.
Media briefing at 4:30 p.m. at Criminal Justice Center at 6th and Canyon.
All Pets Animal Hospital is taking small animals. 303-499-5335. 5290 Manhattan Circle.
Fire is estimated to be 200-300 acres.
June 26 – 3:45 p.m. Road Closures – Bison Drive, Flagstaff Rd.
Road closures:
Bison Drive from 1000 block West
Flagstaff Rd. from Baseline & 6th Ave
Hard closures. No public access allowed. Residents are urged to take vital records and proof of residency when they leave.
June 26 – 3:28 p.m. – Flagstaff Fire evacuations ordered
Sheriff’s Command has issued evacuation orders for approximately 26 households in the area of Bison Drive and Pine Needle Notch subdivision. An evacuation point is being established at New Vista High School at 700 20th Street near Broadway and Baseline. Red Cross is on its way. Residents are advised to take vital records, proof of residency and all pets with them.
Follow #FlagstaffFire on Twitter
June 25 3:18 p.m. – Flagstaff Road is restricted to fire response
Flagstaff Rd. is being used for transport of firefighting equipment. Public access will be restricted or closed along this road until further notice.
June 26 – 3:01 p.m. Bison Fire
A helicopter and heavy air tanker are working on the Bison Fire which is estimated at 6 acres and growing. Smoke can be seen from the city of Boulder and surrounding areas. Rocky Mountain Fire is in charge of the fire.
Fire in Boulder County – June 26 – 2:51 p.m.
There is a fire burning near Bison Drive east of Walker Ranch in the foothills of southern Boulder County. A heavy air tanker is en route and 39 pre-evacuation notices have been sent to residents on Bison Drive and in the Pine Needle Notch subdivision.
Related posts:
Body found, search ends, sheriff won’t confirm ID
0June 24, 2012
The body of missing CU student Nicholas Valore was presumably found in the Flatirons west of NCAR Friday at the base of a steep, rocky ridge. He had been missing since Sunday when he told friends he was going hiking. Fellow classmates alerted authorities that he had not returned by Thursday, His car was subsequently found in the NCAR parking lot. His hiking gear was not in the car.
Related posts:
CU student missing in the Flatirons
0June 22, 2012
University of Colorado student missing; Boulder police ask for public assistance
Search efforts are underway west of Boulder for a 19-year-old University of Colorado student who has been missing since June 17, 2012.
Police found Nicholas Marc Valore’s vehicle parked at the NCAR parking lot last night, after they were notified that Valore might be missing. There are no signs of foul play.
A classmate of Valore’s contacted University of Colorado police late yesterday afternoon to report that he hadn’t seen Valore in classes this week. He was concerned because it was unlike Valore to miss class. CU police were able to locate Valore’s 2004 blue Audi TT Roadster at NCAR, a favorite hiking area of Valore’s. Because NCAR is in the city’s jurisdiction, CU police contacted Boulder police, who are conducting the investigation.
Police contacted Valore’s roommate and Valore’s family members, and no one has heard from him since Father’s Day.
Valore is an avid hiker, and usually wears cargo shorts, a T-shirt and a bright-colored hoodie while hiking. He also carries a black, JanSport backpack. Police have searched Valore’s residence, and it appears that he took some of his hiking gear with him. The hiking gear and clothing was not found in the car.
Search and rescue teams have been looking in the foothills west of NCAR for any sign of Valore. He has been known to hike in the “bouldering” area west of NCAR, and also likes an area known as Mallory Cave. The Boulder County Sheriff’s Office is coordinating the search effort with assistance from Rocky Mountain Rescue, Boulder Open Space & Mountain Parks rangers and Front Range Rescue Dogs.
A photo of Nicholas Valore is attached. Police are asking anyone who may have seen Valore hiking near NCAR or who may have been in contact with him to call police Dispatch at 303.441.3333.
Related posts:
CU study: Little Ice Age caused by four massive volcanoes
0January 30, 2012
New CU-led study may answer long-standing
questions about enigmatic Little Ice Age
A new University of Colorado Boulder-led study appears to answer contentious questions about the onset and cause of Earth’s Little Ice Age, a period of cooling temperatures that began after the Middle Ages and lasted into the late 19th century.
According to the new study, the Little Ice Age began abruptly between A.D. 1275 and 1300, triggered by repeated, explosive volcanism and sustained by a self- perpetuating sea ice-ocean feedback system in the North Atlantic Ocean, according to CU-Boulder Professor Gifford Miller, who led the study. The primary evidence comes from radiocarbon dates from dead vegetation emerging from rapidly melting icecaps on Baffin Island in the Canadian Arctic, combined with ice and sediment core data from the poles and Iceland and from sea ice climate model simulations, said Miller.
While scientific estimates regarding the onset of the Little Ice Age range from the 13th century to the 16th century, there is little consensus, said Miller. There is evidence the Little Ice Age affected places as far away as South America and China, although it was particularly evident in northern Europe. Advancing glaciers in mountain valleys destroyed towns, and famous paintings from the period depict people ice skating on the Thames River in London and canals in the Netherlands, waterways that were ice-free in winter before and after the Little Ice Age.
“The dominant way scientists have defined the Little Ice Age is by the expansion of big valley glaciers in the Alps and in Norway,” said Miller. “But the time it took for European glaciers to advance far enough to demolish villages would have been long after the onset of the cold period,” said Miller, a fellow at CU’s Institute of Arctic and Alpine Research.
Most scientists think the Little Ice Age was caused either by decreased summer solar radiation, erupting volcanoes that cooled the planet by ejecting shiny aerosol particles that reflected sunlight back into space, or a combination of both, said Miller.
The new study suggests that the onset of the Little Ice Age was caused by an unusual, 50-year-long episode of four massive tropical volcanic eruptions. Climate models used in the new study showed that the persistence of cold summers following the eruptions is best explained by a sea ice-ocean feedback system originating in the North Atlantic Ocean.
“This is the first time anyone has clearly identified the specific onset of the cold times marking the start of the Little Ice Age,” said Miller. “We also have provided an understandable climate feedback system that explains how this cold period could be sustained for a long period of time. If the climate system is hit again and again by cold conditions over a relatively short period — in this case, from volcanic eruptions — there appears to be a cumulative cooling effect.”
A paper on the subject is being published Jan. 31 in Geophysical Research Letters, a publication of the American Geophysical Union. The paper was authored by scientists and students from CU-Boulder, the National Center for Atmospheric Research in Boulder, the University of Iceland, the University of California, Irvine, and the University of Edinburgh in Scotland. The study was funded in part by the National Science Foundation and the Icelandic Science Foundation.
As part of the study, Miller and his colleagues radiocarbon-dated roughly 150 samples of dead plant material with roots intact collected from beneath receding ice margins of ice caps on Baffin Island. There was a large cluster of “kill dates” between A.D. 1275 and 1300, indicating the plants had been frozen and engulfed by ice during a relatively sudden event.
Both low-lying and higher altitude plants all died at roughly the same time, indicating the onset of the Little Ice Age on Baffin Island — the fifth largest island in the world — was abrupt. The team saw a second spike in plant kill dates at about A.D. 1450, indicating the quick onset of a second major cooling event.
To broaden the study, the team analyzed sediment cores from a glacial lake linked to the 367-square-mile Langjökull ice cap in the central highlands of Iceland that reaches nearly a mile high. The annual layers in the cores — which can be reliably dated by using tephra deposits from known historic volcanic eruptions on Iceland going back more than 1,000 years — suddenly became thicker in the late 13th century and again in the 15th century due to increased erosion caused by the expansion of the ice cap as the climate cooled, he said.
“That showed us the signal we got from Baffin Island was not just a local signal, it was a North Atlantic signal,” said Miller. “This gave us a great deal more confidence that there was a major perturbation to the Northern Hemisphere climate near the end of the 13th century.” Average summer temperatures in the Northern Hemisphere did not return to those of the Middle Ages until the 20th century, and the temperatures of the Middle Ages are now exceeded in many areas, he said.
The team used the NCAR-based Community Climate System Model to test the effects of volcanic cooling on Arctic sea ice extent and mass. The model, which simulated various sea ice conditions from about A.D. 1150-1700, showed several large, closely spaced eruptions could have cooled the Northern Hemisphere enough to trigger Arctic sea ice growth.
The models showed sustained cooling from volcanoes would have sent some of the expanding Arctic sea ice down along the eastern coast of Greenland until it eventually melted in the North Atlantic. Since sea ice contains almost no salt, when it melted the surface water became less dense, preventing it from mixing with deeper North Atlantic water. This weakened heat transport back to the Arctic and creating a self-sustaining feedback system on the sea ice long after the effects of the volcanic aerosols subsided, he said.
“Our simulations showed that the volcanic eruptions may have had a profound cooling effect,” says NCAR scientist Bette Otto-Bliesner, a co-author of the study. “The eruptions could have triggered a chain reaction, affecting sea ice and ocean currents in a way that lowered temperatures for centuries.”
The researchers set the solar radiation at a constant level in the climate models, and Miller said the Little Ice Age likely would have occurred without decreased summer solar radiation at the time. “Estimates of the sun’s variability over time are getting smaller, it’s now thought by some scientists to have varied little more in the last millennia than during a standard 11-year solar cycle,” he said.
One of the primary questions pertaining to the Little Ice Age is how unusual the warming of Earth is today, he said. A previous study led by Miller in 2008 on Baffin Island indicated temperatures today are the warmest in at least 2,000 years.
Other co-authors on the paper include CU-Boulder’s Yafang Zhong, Darren Larsen, Kurt Refsnider, Scott Lehman and Chance Anderson, NCAR’s Marika Holland and David Bailey, the University of Iceland’s Áslaug Geirsdóttir, Helgi Bjornsson and Darren Larsen, UC-Irvine’s John Southon and the University of Edinburgh’s Thorvaldur Thordarson. Larsen is doctoral student jointly at CU-Boulder and the University of Iceland.
-
Related posts:
The eagles and falcons are coming to Boulder Flatirons, open space
0January 24, 2012
Open Space and Mountain Parks begins seasonal cliff-nesting raptor closures
The City of Boulder’s Open Space and Mountain Parks (OSMP) Department is temporarily closing areas in order to protect nesting and roosting raptors. The following areas and formations will be closed from Feb. 1 through July 31:
Golden eagle feeding a chick
- Lefthand Canyon Palisades, at the intersection of Lefthand Canyon Drive and Olde Stage Road (Buckingham picnic area remains open);
- Mount Sanitas, First Buttress, accessible from the Mount Sanitas trailhead, .5 miles west of Fourth Street and Mapleton Avenue (no closures to the bouldering areas along the ridge; Mount Sanitas trail will remain open);
- Gregory Canyon Amphitheater, including the Amphitheater Express Trail and the 3rd Pinnacle (the Amphitheater Trail to Saddle Rock will remain open);
- Third Flatiron, including the East and West Ironing Boards, Queen Anne’s Head and Jaws, and WC Pinnacle, accessible from Chautauqua trailhead;
- Flagstaff Mountain: the north side of Flagstaff Mountain will be closed (the Boy Scout Trail will remain open);
- Skunk Canyon, including Ridge 2, 3 and 4, the Aechean Pronouncement, the Dreadnaught, the North Ridge and the entirety of Sacred Cliffs, accessible from NCAR trailhead at the west end of Table Mesa Road;
- The Back Porch and The Box, accessible from the NCAR trailhead at the west end of Table Mesa Road;
- Bear Creek Spire, accessible from the NCAR trailhead at the west end of Table Mesa Road;
- Fern Canyon, accessible from the NCAR trailhead at the west end of Table Mesa Road (the designated Fern Canyon hiking trail will remain open);
- Shadow Canyon and the Matron, accessible from the South Mesa Trailhead (the Maiden will remain open and accessible from the east and the designated Shadow Canyon hiking trail will remain open);
- The Sphinx, accessible from the NCAR trailhead at the west end of Table Mesa Road;
- Diamond Head and SoBo Buttress, west of Shadow Canyon, accessible from South Mesa Trailhead (South Boulder Peak Trail will remain open);
- The entire Mickey Mouse wall, accessible from the Goshawk Ridge Trail.
High-quality cliff habitat and rich food resources on OSMP lands, as well as community cooperation to protect nesting sites, sustains the mountain backdrop as a regionally important area for nesting falcons and golden eagles. OSMP volunteers and staff have been monitoring raptor nesting and roosting areas since 1984 and the program is an integral part in protecting the species and adaptively managing the closures.
Trespass violations can result in a summons with penalties up to 90 days in jail and/or a $1,000 fine. OSMP relies heavily on the public to respect the closures, and the cooperation of visitors to these areas is greatly appreciated. Closures may be lifted early if no raptor activity is observed at these sites.
Up-to-date information on raptor closures and closure maps can be found on the Open Space and Mountain Parks’ Web site: www.osmp.org. or call 303-441-3440.
Related posts:
CU study: less hail may increase flooding on Front Range
0January 9, 2012
STUDY INDICATES HAIL MAY DISAPPEAR
FROM COLORADO’S FRONT RANGE BY 2070
Summertime hail could all but disappear from the eastern flank of Colorado’s Rocky Mountains by 2070, says a new study by the National Oceanic and Atmospheric Administration, the University of Colorado Boulder’s Cooperative Institute for Research in Environmental Sciences and the National Center for Atmospheric Research.
Less hail damage could be good news for gardeners and farmers, said lead author Kelly Mahoney, a research scientist at CIRES, but a shift from hail to rain can also mean more runoff, which could raise the risk of flash floods. “In this region of elevated terrain, hail may lessen the risk of flooding because it takes awhile to melt,” Mahoney said. “Decision makers may not want to count on that in the future.”
For the new study, published this week in the journal Nature Climate Change, Mahoney and her colleagues used “downscaling” techniques to try to understand how climate change might affect hail-producing weather patterns across Colorado.
The research focused on storms involving pea-sized and smaller hailstones on Colorado’s Front Range, a region that stretches from the foothill communities of Colorado Springs, Denver and Fort Collins up to the Continental Divide. Colorado’s most damaging hailstorms tend to occur further east and involve larger hailstones not examined in this study.
In the summer in Colorado’s Front Range above about 7,500 feet, precipitation commonly falls as hail. Decision makers concerned about the safety of mountain dams and flood risk have been interested in how climate change may affect the amount and nature of precipitation in the region.
Mahoney and her colleagues began exploring that question with results from two climate models, which assumed that levels of climate-warming greenhouse gases will continue to increase in the future, from about 390 parts per million in the atmosphere today to about 620 parts per million in 2070.
But the weather processes that form hail, like thunderstorms, occur on much smaller scales than can be reproduced by global climate models. So the team “downscaled” the global model results twice: first to regional-scale models that can take regional topography and other details into account, then again to weather-scale models that can resolve individual storms and even the cloud processes that create hail. The regional-scale topography step was completed as part of NCAR’s North American Regional Climate Change Assessment Program.
Finally, the team compared the hailstorms of the future, from 2041 to 2070, to those of the past, from 1971 to 2000, as captured by the same sets of downscaled models. Results were similar in experiments with both climate models.
“We found a near elimination of hail at the surface,” Mahoney said.
In the future, increasingly intense storms may actually produce more hail inside clouds, the team found. However, because those relatively small hailstones fall through a warmer atmosphere, they melt quickly, falling as rain at the surface or evaporating back into the atmosphere. In some regions, simulated hail fell through an additional 1,500 feet of above-freezing air in the future as compared with the past.
The research team also found evidence that precipitation events over Colorado become more extreme in the future, while changes in hail may depend on the size of the hailstones — results that will be explored in more detail in ongoing work.
Mahoney’s postdoctoral research was supported by the Postdocs Applying Climate Expertise, or PACE, program administered by the University Corporation for Atmospheric Research and funded by CIRES Western Water Assessment, NOAA and the U.S. Bureau of Reclamation. PACE connects young climate scientists with real-world problems such as those faced by water resource managers.
Co-authors of the new paper include James Scott and Joseph Barsugli of CIRES and NOAA, Michael Alexander of the NOAA Earth System Research Laboratory and Gregory Thompson of NCAR.
