|
Dirty snow may warm Arctic as much as greenhouse gases
June 07, 2007The global warming debate has focused on carbon dioxide emissions, but scientists at UC Irvine have determined that a lesser-known mechanism - dirty snow - can explain one-third or more of the Arctic warming primarily attributed to greenhouse gases.
Snow becomes dirty when soot from tailpipes, smoke stacks and forest fires enters the atmosphere and falls to the ground. Soot-infused snow is darker than natural snow. Dark surfaces absorb sunlight and cause warming, while bright surfaces reflect heat back into space and cause cooling.
"When we inject dirty particles into the atmosphere and they fall onto snow, the net effect is we warm the polar latitudes," said Charlie Zender, associate professor of Earth system science at UCI and co-author of the study. "Dark soot can heat up quickly. It's like placing tiny toaster ovens into the snow pack."
The study appears this week in the Journal of Geophysical Research.
Dirty snow has had a significant impact on climate warming since the Industrial Revolution. In the past 200 years, the Earth has warmed about .8 degree Celsius. Zender, graduate student Mark Flanner, and their colleagues calculated that dirty snow caused the Earth's temperature to rise .1 to .15 degree, or up to 19 percent of the total warming.
In the past two centuries, the Arctic has warmed about 1.6 degrees. Dirty snow caused .5 to 1.5 degrees of warming, or up to 94 percent of the observed change, the scientists determined.
The amount of warming by dirty snow varied from year to year, with higher temperatures in years with many forest fires. Greenhouse gases, which trap outgoing energy, are primarily responsible for the remaining temperature increase and are considered the Earth's most important overall climate changing mechanism. Other human influences on Arctic climate change are particles in the atmosphere, including soot; clouds; and land use.
Humans create the majority of airborne soot through industry and fuel combustion, while forest and open-field fires account for the rest. Because of human activity, greenhouse gas levels have increased by one-third in the last two centuries.
"A one-third change in concentration is huge, yet the Earth has only warmed about .8 degrees because the effect is distributed globally," Zender said. "A small amount of snow impurities in the Arctic have caused a significant temperature response there."
Previous studies have analyzed dirty snow's effect on climate, but this is the first to take into account realistic emissions from forest fires in the Northern Hemisphere and how warming affects the thickness of the snow pack.
In some polar areas, impurities in the snow have caused enough melting to expose underlying sea ice or soil that is significantly darker than the snow. The darker surfaces absorb sunlight more rapidly than snow, causing additional warming. This cycle causes temperatures in the polar regions to rise as much as 3 degrees Celsius during some seasons, the scientists say.
"Once the snow is gone, the soot that caused the snow to melt continues to have an effect because the ground surface is darker and retains more heat," Zender said.
Dirty snow is prevalent in East Asia, Northern Europe and Northeastern United States.
Zender believes policymakers could use these research results to develop regulations to mitigate global warming. Limiting industrial soot emissions and switching to cleaner-burning fuels would leave snow brighter, he says. New snow falls each year, and if it contained fewer impurities, the ground would brighten and temperatures would cool. Carbon dioxide lives in the atmosphere for a century, so cutting back on emissions can prevent further warming but does not produce immediate cooling.
UCI scientist James Randerson and Philip Rasch, a scientist at the National Center for Atmospheric Research in Boulder, Colo., also worked on the study. The National Science Foundation and NASA funded this research.
University of California, Irvine
The study appears this week in the Journal of Geophysical Research.
Dirty snow has had a significant impact on climate warming since the Industrial Revolution. In the past 200 years, the Earth has warmed about .8 degree Celsius. Zender, graduate student Mark Flanner, and their colleagues calculated that dirty snow caused the Earth's temperature to rise .1 to .15 degree, or up to 19 percent of the total warming.
In the past two centuries, the Arctic has warmed about 1.6 degrees. Dirty snow caused .5 to 1.5 degrees of warming, or up to 94 percent of the observed change, the scientists determined.
The amount of warming by dirty snow varied from year to year, with higher temperatures in years with many forest fires. Greenhouse gases, which trap outgoing energy, are primarily responsible for the remaining temperature increase and are considered the Earth's most important overall climate changing mechanism. Other human influences on Arctic climate change are particles in the atmosphere, including soot; clouds; and land use.
Humans create the majority of airborne soot through industry and fuel combustion, while forest and open-field fires account for the rest. Because of human activity, greenhouse gas levels have increased by one-third in the last two centuries.
"A one-third change in concentration is huge, yet the Earth has only warmed about .8 degrees because the effect is distributed globally," Zender said. "A small amount of snow impurities in the Arctic have caused a significant temperature response there."
Previous studies have analyzed dirty snow's effect on climate, but this is the first to take into account realistic emissions from forest fires in the Northern Hemisphere and how warming affects the thickness of the snow pack.
In some polar areas, impurities in the snow have caused enough melting to expose underlying sea ice or soil that is significantly darker than the snow. The darker surfaces absorb sunlight more rapidly than snow, causing additional warming. This cycle causes temperatures in the polar regions to rise as much as 3 degrees Celsius during some seasons, the scientists say.
"Once the snow is gone, the soot that caused the snow to melt continues to have an effect because the ground surface is darker and retains more heat," Zender said.
Dirty snow is prevalent in East Asia, Northern Europe and Northeastern United States.
Zender believes policymakers could use these research results to develop regulations to mitigate global warming. Limiting industrial soot emissions and switching to cleaner-burning fuels would leave snow brighter, he says. New snow falls each year, and if it contained fewer impurities, the ground would brighten and temperatures would cool. Carbon dioxide lives in the atmosphere for a century, so cutting back on emissions can prevent further warming but does not produce immediate cooling.
UCI scientist James Randerson and Philip Rasch, a scientist at the National Center for Atmospheric Research in Boulder, Colo., also worked on the study. The National Science Foundation and NASA funded this research.
University of California, Irvine
Greenhouse Gas News and Current Greenhouse Gas Events RSSAction needed now for Minnesota to reach goals in reducing greenhouse gas emissions by 2015
The state of Minnesota must act now if it wants to reach its Minnesota Next Generation Energy Act goals of reducing greenhouse gas emissions by 15 percent by 2015, according to a team of University of Minnesota transportation and public policy researchers.
Fuel from food waste: bacteria provide power
Researchers have combined the efforts of two kinds of bacteria to produce hydrogen in a bioreactor, with the product from one providing food for the other.
Study: Future snowmelt in West twice as early as expected; threatens ecosystems and water reserves
According to a new study, global warming could lead to larger changes in snowmelt in the western United States than was previously thought, possibly increasing wildfire risk and creating new water management challenges for agriculture, ecosystems and urban populations.
Shrinking carbon footprints
Would shrinking your carbon footprint, recycling more, and going green be easier if you could monitor your household's environmental impact?
Major progress in technology needed for 25 percent renewable energy use to be affordable
Dramatic progress in renewable energy technology is needed if the United States desires to produce 25 percent of its electricity and motor vehicle fuel from renewable sources by 2025 without significantly increasing consumer costs.
Climate change could severely impact California's unique native plants
The native plants unique to California are so vulnerable to global climate change that two-thirds of these "endemics" could suffer more than an 80 percent reduction in geographic range by the end of the century.
Floridians believe global warming will have dangerous impacts on the state
A new survey of Floridians finds that most are convinced that global warming is happening now and that more should be done by key leaders to help Florida deal with climate change.
Plan to conserve forests may be detrimental to other ecosystems
Conserving biodiversity must be considered when developing plans to reduce greenhouse gas emissions from deforestation, researchers warn in today's edition of Science.
Permafrost Threatened by Rapid Retreat of Arctic Sea Ice, NCAR Study Finds
The rate of climate warming over northern Alaska, Canada, and Russia could more than triple during periods of rapid sea ice loss, according to a new study led by the National Center for Atmospheric Research (NCAR).
Carbon emissions trading in Europe: Lessons to be learned
For the past three years, the European Union has been operating the world's largest emissions trading system and the first system to limit and to trade carbon dioxide emissions.
More Greenhouse Gas News Articles
| © 2008 BrightSurf.com |