Global Warming

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Tiny Ocean Creatures Tell of Global Warming

Sediment cores collected from the seafloor off Southern California suggest that plankton populations in the Northeastern Pacific have changed significantly since the early 1900s. Scientists say these changes parallel a general warming trend starting at that time.

Subtropical and tropical species of small marine organisms called foraminifera seemed to become more abundant as ocean temperatures increased, researchers said. At the same time, similar species living in cooler waters seemed to become less abundant. Changes in the last 30 years are unlike anything found in sediment evidence from the past 1,400 years, the scientists said.

"These data show that ocean warming has affected foram populations prior to the late twentieth century," said study co-author David Field of the University of California, San Diego. "However, changes since the 1970s have been particularly unusual, and show that ocean ecosystems in the northeastern Pacific have passed some threshold of natural variability."

The foraminifera studied are small, amoeba-like organisms that live inside tiny shells called "tests," several of which might fit on the head of pin. Most forams live near the surface of the ocean, with different species living in ocean waters of different temperatures. When they die, their shells sink to the seafloor, often mixing with the sediment there to form distinct annual layers similar to growth rings in a tree. In some areas those annual layers remain relatively intact for millennia.

This study provides the kind of long-term data needed to clarify whether the warming trend and ecosystem changes are within the range of natural variability, or are the result of human activities.

This research is detailed in the Jan. 6 issue of the journal Science

Courtesy: http://www.livescience.com/imageoftheday/siod_060109.html

Credit: Scripps Institution of Oceanography

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An extraordinary burst of global warming that occurred around 55 million years ago dramatically reversed Earth’s pattern of ocean currents, a finding that strengthens modern-day concern about climate change, a study says.

The big event, the Palaeocene/Eocene Thermal Maximum (PETM), saw the planet’s surface temperature rise by between five and eight degrees C (nine and 16.2 F) in a very short time, unleashing climate shifts that endured tens of thousands of years.

Scientists Flavia Nunes and Richard Norris of the Scripps Institution of Oceanography in California explored how these warmer temperatures might have affected ocean currents.

They measured carbon-13 isotopes from 14 cores that had been drilled into the deep floor in four different ocean basins, taking samples from sediment layers deposited before, during and after the PETM.

These isotopes are considered to be an indicator of the nutrients deposited by the water at the time. The higher the isotope value, the likelier that the source came from the deep ocean, the prime source for nutrients. With a painstaking reconstruction, Nunes and Norris found that the world’s ocean current system did a U-turn during the PETM — and then, ultimately, reversed itself. Before the PETM, deep water upwelled in the southern hemisphere; over about 40,000 years, the source of this upwelling shifted to the northern hemisphere; it took another 100,000 years before recovering completely.

What unleashed the PETM is unclear. Most fingers of blame point to volcanic eruptions that disgorged gigatonnes of carbon dioxide, or coastal reservoirs of methane gas, sealed by icy soil, that were breached by warmer temperatures or receding seas.

The huge temperature rise may have occurred within just few thousand years, but as Nunes and Norris point out, the effects were enduring and the lesson for mankind today is clear. “Modern CO2 input to the biosphere from fossil fuel sources is approaching that estimated for the PETM, raising concerns about future climate and circulation change,” they warn. “The PETM example shows that anthropogenic (man-made) forcing may have lasting effects not only in global climate but in deep-ocean circulation as well.”

The study, which appears on Thursday in the British journal Nature, comes on the heels of research published in November which suggests that global warming is slowing the Atlantic current that gives western Europe its mild climate. The suspected reason for this is an inrush of freshwater into the northern Atlantic, caused by melting glaciers in Greenland and melting sea ice, and higher flow into the Arctic from Siberian rivers caused by greater rainfall.

The influx brakes the conveyor belt in which warm surface water is taken up to the northeastern Atlantic from the tropics before returning down to the southern hemisphere as cool, deep-sea water. In 2001, the UN’s top scientific authority on global warming, the Intergovernmental Panel on Climate Change (IPCC), estimated that there would be a temperature rise of 1.4 to 5.8 C (2.5 to 10.4 F) from 1990-2100. The increase was predicted according to scenarios of atmospheric carbon dioxide (CO2), ranging from 540 to 970 parts per million (ppm). That compares with 280ppm for pre-industrial times and around 380ppm today, which is already the highest concentration of CO2 for 650,000 years.


Courtesy: http://www.dailytimes.com.pk/default.asp?page=2006%5C01%5C09%5Cstory_9-1-2006_pg6_15

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GLOBAL warming will cause sea levels to rise up to 34cm by the end of the century, causing increased flooding and coastal erosion, according to a new study by Australian researchers.

The study, published in this month's issue of the journal Geophysical Research Letters, said global warming was expected to further heat up the world's oceans and cause glaciers in the Himalayas and ice sheets in Greenland to melt.

The study estimated sea levels would increase between 28cm and 34cm by 2100.
http://www.thecouriermail.news.com.au/common/story_page/0,5936,17955517%255E954,00.html


Download the attached paper

[rocksea]

GLOBAL warming will cause sea levels to rise up to 34cm by the end of the century by the end of the century only? i thought it was imminent :rolleyes:

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Ocean plants show effects of warming

University of Hawaii researchers are reporting that tiny ocean plants called phytoplankton can be affected by global warming, according to a study published recently in Nature magazine.

The increase in ocean temperature produced by global warming causes less dense warm water at the surface to rise and limits the mixing with the colder water found deeper in the ocean. The analysis suggests that reduced vertical mixing could cause the deep water layers of phytoplankton to oscillate and shift, the University of Hawaii reported in a news release.
The discovery that the layers of phytoplankton are unstable during climate shifts indicates that the plankton can inspire further warming, the news release continued. The results could come as a surprise to scientists who had generally assumed that these plankton bands were relatively stable.
The study was conducted by microbial biologist and oceanographer David Karl from the School of Ocean and Earth Science and Technology, along with colleagues from the Netherlands. They used climate models to correlate with observations at Station Aloha, a site about 62 miles north of Hawaii where physical, biological and chemical measurements of the water column have been taken for the past 20 years.

"Deep chlorophyll layers have been known to occur in the sea for nearly a century, though we are not absolutely certain why they form, what sustains them and what temporal dynamics, if any, they have," Karl said.
"The lack of vertical mixing in the ocean due to climate variability and greenhouse gas-induced warming are already upon us," Karl continued. "We are effectively in the middle of a large, global-scale experiment with only a very basic and incomplete understanding of the processes and controls of ocean plankton dynamics. What will happen when the surface ocean changes its acidity? What will happen when human activities and land use practices begin to influence the amount of fixed nitrogen entering the coastal zone or the amount of iron-rich dust in the atmosphere? These are important, unresolved questions that will need to be addressed."


http://starbulletin.com/2006/01/30/news/story07.html

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Sydney, Australia (AHN) - Australia's hot summer has had a devastating effect on the ecologically sensitive Great Barrier Reef.

Water temperatures during the past four months had been well above normal and the reef is following a similar temperature profile of 2001-2002, which led to the worst incidence of coral bleaching to the spectacular natural formation.

The University of Queensland scientists say the underwater scene shocked them and are fearful the entire reef may be at risk of destruction from global warming.

Professor Ove Hoegh-Guldberg reports most of the reefs the team saw are now completely bleached.

He continues, "Going down to 10 meters, every pieces of coral was a glowing white color - all that brown color had disappeared and that was surprising for us.”

Researchers believe they reefs may be saved with two months of cyclonic stormy weather that can churn up colder deeper weather

The last severe cases of this bleaching phenomenon occurred in 1998 and 2002, the last leaving more than 5 percent of the reef destroyed

http://www.allheadlinenews.com/articles/7002184650

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LONDON (Reuters) - Two major glaciers in Greenland have recently begun to flow and break up more quickly under the onslaught of global warming, a new study said on Friday, raising the specter of millions drowning from rising sea levels.

The report from the University of Swansea's School of the Environment and Society said the Kangerdlugssuaq and Helheim glaciers had doubled their rate of flow to the ocean over the past two years after steady movement during the 1990s.

This spurt meant that current environmental models of the rate of retreat of Greenland's giant ice sheet -- which could add seven meters to the height of the world's oceans if it disappears -- had underestimated the problem.

"It seems likely that other Greenland outlets will undergo similar changes, which would impact the mass balance of the ice sheet more rapidly than predicted," the study said.

It said the fact that the two major outflow glaciers had shown the same sudden acceleration despite being more than 300 km apart suggested the cause was not local but more likely climatic or oceanic in origin.

"In both of these glaciers the acceleration and retreat has been sudden, despite the progressive nature of warming and thinning over some years," the report said.

"The longevity of this flux increase is unknown but could be substantial," it added.

The report followed a warning earlier this week from Britain's Hadley Center for Climate Prediction and Research -- a branch of the Meteorological Office -- that the Greenland ice sheet could be disappearing faster than previously thought.

The ice sheet contains one-tenth of the world's freshwater reserves.

Scientists predict that global average temperatures will rise by between one and six degrees Celsius this century unless urgent action is taken now to cap and reduce carbon emissions.

Even a rise of three degrees could result in cataclysmic species loss, melting polar icecaps raising sea levels by many meters and wholesale famine and disease.

Greenland is only part of the picture, and there is also evidence of local warming and melting on the giant Western Antarctic ice sheet.

Scientists said on Monday the world had to halt greenhouse gas emissions and reverse them within two decades or watch the planet spiralling toward destruction.

The first phase of the global Kyoto protocol on cutting greenhouse gas emissions runs until 2012, and negotiations have only just started on finding a way of taking it beyond that.

The United States, the world's biggest polluter, has rejected both the protocol in its current form and any suggestion of expanding or extending it.

http://news.yahoo.com/s/nm/20060203/sc_nm/environment_greenland_dc

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Ocean temperatures might have risen even higher during the last century if it weren't for volcanoes that spewed ashes and aerosols into the upper atmosphere, researchers have found. The eruptions also offset a large percentage of sea level rise caused by human activity.

Using 12 new state-of-the-art climate models, the researchers found that ocean warming and sea level rise in the 20th century were substantially reduced by the 1883 eruption of the Krakatoa volcano in Indonesia. Volcanic aerosols blocked sunlight and caused the ocean surface to cool.

"That cooling penetrated into deeper layers of the ocean, where it remained for decades after the event," said Peter Gleckler, an atmospheric scientist at Lawrence Livermore National Laboratory (LLNL). "We found that volcanic effects on sea level can persist for many decades."

Gleckler, along with LLNL colleagues Ben Santer, Karl Taylor and Krishna AchutaRao and collaborators from the National Center for Atmospheric Research, the University of Reading and the Hadley Centre, tested the effects of volcanic eruptions on recent climate models. They examined model simulations of the climate from 1880 to 2000, comparing them with available observations.

External "forcings," such as changes in greenhouse gases, solar irradiance, sulphate and volcanic aerosols, were included in the models.

Oceans expand and contract depending on the ocean temperature. This causes sea level to increase when the water is warmer and to recede in cooler temperatures.

The volume average temperature of oceans (down to 300 meters) worldwide has warmed by roughly .037 degrees Celsius in recent decades due to increasing atmospheric greenhouse gases. While seemingly small, this corresponds to a sea level rise of several centimeters and does not include the effect of other factors such as melting glaciers. That sea level jump, however, would have been even greater if it weren't for volcanic eruptions over the last century, Gleckler said.

"The ocean warming suddenly drops," he said. "Volcanoes have a big impact. The ocean warming and sea level would have risen much more if it weren't for volcanoes."

Volcanic aerosols scatter sunlight and cause the ocean surface temperature to cool, an anomaly that is gradually subducted into deeper layers, where it remains for decades.

The experiments studied by Gleckler's team also included the more recent 1991 Mt. Pinatubo eruption in the Philippines, which was comparable to Krakatoa in terms of its size and intensity. While similar ocean surface cooling resulted from both eruptions, the heat-content recovery occurred much more quickly in the case of Pinatubo.

"The heat content effects of Pinatubo and other eruptions in the late 20th century are offset by the observed warming of the upper ocean, which is primarily due to human influences," Gleckler said.

The research appears in the Feb. 9 issue of the journal Nature.

http://www.yubanet.com/artman/publish/article_31563.shtml

http://www.livescience.com/imageoftheday/siod_060210.html

http://www.indiadaily.com/editorial/7146.asp

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British scientists have revealed that temperatures in the northern hemisphere during the 20th century increased across the greatest area seen for a millennium.

Evidence of a dramatic jump in the number of hotspots was uncovered from a variety of sources including tree rings, ice cores and diaries dating back 750 years.

The work by researchers from the University of East Anglia adds weight to the growing mound of evidence of widespread global warming in recent decades.

Dr Tim Osborn and Professor Keith Briffa said that they found evidence for clearly colder episodes during a period known as the Little Ice Age, from 1580 to 1850.

They also came across evidence of a significantly warmer phase during medieval times, from 890 to 1170, the team reports in the journal Science.

But their key finding was that in the 20th century, the northern hemisphere experienced unusually widespread warmth compared with all the natural warming and cooling episodes of the past 1,200 years.

The team managed to gather evidence of temperature patterns as far back as the ninth century from a variety of natural sources, including measurements of the rings in long-lived evergreen trees growing in Scandinavia, Siberia and the Rockies.

Warmer temperatures cause the trees to lay down wider rings, which can be measured by coring.

Greenland ice sheets also provided proxy records of temperatures, as the chemical composition of the ice varies with the climate conditions in place when each layer was accumulated.

Using naturally occurring proxy temperature measurements is an established method of climate research. The scientists verified the ice and tree records were accurate by comparing 20th century naturally occurring records with thermometer measurements for the same period.

The diaries of people living in the Netherlands and Belgium over the past 750 years also yielded crucial information such as which years the canals froze.

Credits: National News

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Greenland's glaciers are sliding towards the sea much faster than previously believed, scientists have told a conference in St Louis, US.

It was thought the entire Greenland ice sheet could melt in about 1,000 years, but the latest evidence suggests that could happen much sooner.

It implies that sea levels will rise a great deal faster as well.

Details of the study, by Nasa and University of Kansas researchers, are also reported in the journal Science.

The comprehensive analysis found that the amount of ice dumped into the Atlantic Ocean has doubled in the last five years.

If the Greenland ice sheet melted completely, it would raise global sea levels by about 7m.

Greenland's contribution to global sea level rise today is two to three times greater than it was in 1996.

Sleeping giant

"We are concerned because we know that sea levels have been able to rise much faster in the past - 10 times faster. This is a big gorilla. If sea level rise is multiplied by 10 or more, I'm not sure we can deal with that," co-author Eric Rignot, from the US space agency's (Nasa) Jet Propulsion Laboratory in California, told the BBC News website.

Previous estimates suggested it would take many hundreds of years for the Greenland ice sheet to melt completely. The new data will cut this timescale, but by how much is uncertain.


"It depends on how fast the glaciers can go and how sustainable the acceleration can be," said Dr Rignot.

He added: "It takes a long time to build and melt an ice sheet, but glaciers can react quickly to temperature changes."

In 1996, Greenland was losing about 100 cubic km per year in mass from its ice sheet. In 2005, this had increased to about 220 cubic km. By comparison, the city of Los Angeles uses about one cubic km of water per year.

Rising surface air-temperatures seem to be behind the increases in glacier speed in the southern half of Greenland since 1996; but the northward spread of warmer temperatures may be responsible for a rapid increase in glacier speed further north after 2000.

Satellite monitoring

Over the past 20 years, the air temperature in south-east Greenland has risen by 3C.

Warmer temperatures cause more surface melt water to reach the base of the ice sheet where it meets the rock. This is thought to serve as a lubricant, easing the glaciers' march to the sea.



The study's results come from satellites that monitor glacier movement from space.

Rignot and colleague Pannir Kanagaratnam, from the University of Kansas, built up a glacier speed map from the data for 2000 and then used measurements from 1996-2005 to determine how glacier velocity had changed in the last decade.

The researchers plan to continue their monitoring of the Greenland glaciers using satellite data.

The Greenland ice sheet covers 1.7 million sq km and is up to 3km thick.

The scientists described their results at the annual meeting of the American Association for the Advancement of Science.

http://news.bbc.co.uk/2/hi/science/nature/4720536.stm

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Scientists from NASA and Columbia University, New York, have used computer modeling to successfully reproduce an abrupt climate change that took place 8,200 years ago. At that time, the beginning of the current warm period, climate changes were caused by a massive flood of freshwater into the North Atlantic Ocean.

This work is the first to consistently recreate the event by computer modeling, and the first time that the model results have been confirmed by comparison to the climate record, which includes such things as ice core and tree ring data.

"We only have one example of how the climate reacts to changes, the past," said Gavin A. Schmidt, a NASA Goddard Institute for Space Studies (GISS), New York, researcher and co-author on the study. "If we’re going to accurately simulate the Earth’s future, we need to be able to replicate past events. This was a real test of the model’s skill."

The study was led by Allegra LeGrande, a graduate student in the department of Earth and Environmental Sciences at Columbia University. The results appeared in the journal "Proceedings of the National Academy of Sciences" (PNAS) in Jan. 2006.

The group used an atmosphere-ocean coupled climate computer model known as "GISS Model E-R" to simulate the climate impact of a massive freshwater flood into the North Atlantic that happened about 8,200 years ago after the end of the last Ice Age. Retreating glaciers opened a route for two ancient meltwater lakes, known as Agassiz and Ojibway, to suddenly and catastrophically drain from the middle of the North American continent.

At approximately the same time, climate records show that the Earth experienced its last abrupt climate shift. Scientists believe that the massive freshwater pulse interfered with the ocean’s overturning circulation, which distributes heat around the globe. According to the record of what are known as "climate proxies", average air temperatures apparently fell as much as several degrees in some areas of the Northern Hemisphere.

Climate researchers use these proxies, chemical signals locked in minerals and ice bubbles as well as pollen and other biological indicators, as indirect measures of temperature and precipitation patterns in the distant past. Because GISS Model E-R incorporates the response of these proxies in its output, the authors of the PNAS study were able to compare their results directly to the historical record.

The researchers prodded their model with a freshwater flow equal to between 25 and 50 times the flow of the Amazon River in 12 model runs that took more than a year to complete. Although the simulations largely agreed with records from North Atlantic sediment cores and Greenland ice cores, the team’s results showed that the flood had much milder effects around the globe than many people thought.

According to the model, temperatures in the North Atlantic and Greenland showed the largest decrease, with slightly less cooling over parts of North America and Europe. The rest of the northern hemisphere, however, showed very little effect, and temperatures in the southern hemisphere remained largely unchanged. Moreover, ocean circulation, which initially dropped by half after simulated flood, appeared to rebound within 50 to 150 years.

"The flood we looked at was even larger than anything that could happen today," said LeGrande. "Still, it’s important for us to study because the real thing occurred during a period when conditions were not that much different from the present day."

The GISS climate model is also being used for the latest simulations by the Intergovernmental Panel on Climate Change (IPCC) to simulate the Earth’s present and future climate. "Hopefully, successful simulations of the past such as this will increase confidence in the validity of model projections," said Schmidt.

The study was funded by NASA, National Defense Science and Engineering Graduate Fellowship, and the National Science Foundation.

http://www.innovations-report.com/html/reports/earth_sciences/report-55975.html

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New research shows Utah is getting warmer at a rate that's faster than initially thought. Scientists say that's just one more sign of startling changes they're observing all over the globe.

Anyone who lives in the West knows our snow packs aren't what they used to be. Rising temperatures mean what used to fall as snow now often falls as rain. And scientists gathering here in Utah for a conference say we should prepare for more.



Consider extreme weather events like last year's spectacular floods in Southern Utah, shrinking mountain snow packs in the Rockies, Katrina and increased hurricane activity, melting ice sheets at the poles pushing polar bears to the brink. These are all fingerprints of global climate change, according to national experts brought together for this U of U conference.

Henry Pollack/ Prof. of Geophysics. Uni. of Michigan: "Climate change is real. That it's accelerating and it's going to have consequences that aren't all together comfortable."

Scientists are sounding increasingly urgent alarms on a variety of fronts, from melting ice sheets at the poles, to rising temperatures and sea levels, to dramatic changes in the high country of the West.

The National Center for Atmospheric Research has charted global climate trends, finding the world is warming, particularly in the last 30 years.

A recent analysis of Utah's temperature data shows warming is accelerating in Utah--up 3 degrees in just the past 30 years. Rise in precipitation is up 12% in a century.



Fred Wagner/ Prof. Emeritus/ Utah State University: "Things are going to get hotter. Our summers are going to get much warmer. Our winters are going to be milder. We're going to see snow packs in the mountain ranges shrinking, and that's happening over the West as a whole."

In the Arctic, the changes are coming even faster. Consider the loss of sea ice just in the last 30 years.

Mark Serreze/ Senior Research Scientist/ Uni. of Colorado: "We've lost an area of sea ice roughly the size of the state of Alaska."

As changes from around the globe add up, researchers say they see changes in public opinion.

Henry Pollack/ Prof. of Geophysics/ Univ. of Michigan: "I think we're close to a tipping point in term of public awareness of climate change and that humans are playing a big role in it."

Lana Pollack/ Michigan Environmental Council: "And there is a change in attitude. A lot of that is coming from big industry."

In the short run, scientists say conservation will help buy us time so that alternative energy sources can be developed for the long run.

http://www.ksl.com/?nid=148&sid=171272

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The polar ice sheets are thinning, according to the most comprehensive survey ever undertaken of the regions.

Scientists confirm that climate warming is changing how much water remains locked in Earth’s largest storehouse of ice and snow.

Previous studies have illustrated incremental losses of ice in parts of the regions but the new survey is the first to inventory the deficit of ice and the addition of new snow across both continents.

The survey was conducted in a consistent way throughout an entire decade.

Findings showed a net loss of ice from the combined polar ice sheets between 1992 and 2002 and a corresponding rise in sea level.

For the first time, the extensive thinning of the West Antarctic ice shelves, the increase in snowfall in the interior of Greenland and the thinning of the edges was documented.

All are signs of a warming climate predicted by computer models.

The survey, published in the Journal of Glaciology, combines new satellite mapping of the height of the ice sheets from two European Space Agency satellites.

It also used previous Nasa airborne mapping of the edges of the Greenland ice sheets to determine how fast the thickness is changing.

The study of Greenland suggests there was a slight gain in the total mass of frozen water in the ice sheet over the decade studied, contrary to previous assessments.

When the scientists added up the overall gains and loses of ice from the Greenland and Antarctic ice sheets, there was a net loss of ice to the sea.

The amount of water added to the oceans (20 billion tonnes) is equivalent to the total amount of freshwater used in homes, businesses and farming in New York, New Jersey and Virginia each year.

“The study indicates that the contribution of the ice sheets to recent sea-level rise during the decade studied was much smaller than expected, just two percent of the recent increase of nearly three millimetres a year,” said lead author Jay Zwally of Nasa's Goddard Space Flight Centre.

“Continuing research using Nasa satellites and other data will narrow the uncertainties in this important issue.”

Nasa will continue to monitor the polar ice sheets with the Ice, Cloud and land Elevation Satellite (ICESat) that uses a laser beam to measure the elevation of ice sheets three times a year.

Source: scenta
http://www.scenta.co.uk/scenta/news.cfm?cit_id=634953&FAArea1=customWidgets.content_view_1

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Scientists have confirmed that climate warming is changing how much water remains locked in the Antarctic and Greenland ice sheets, according to an article published in the Journal of Glaciology.

Using radar altimeter data from ESA’s ERS-1 and ERS-2, Jay Zwally, a scientist at NASA's Goddard Space Flight Center, and his colleagues mapped the height of the ice sheets and found there was a net loss of ice from the combined sheets between 1992 and 2002 and a corresponding rise in sea level.

Polar ice plays a crucial role in regulating global climate because it reflects about 80 percent of the incoming sunlight. If the ice caps over the polar ocean melt, the ocean water would absorb a large part of the radiation energy, which would lead to further melting of the ice and further warming of the climate.

According to the NASA study, published in the March edition, 20 billion net tonnes of water are added to oceans each year as a result of Greenland’s ice sheet gaining some 11 billion tonnes of water annually, while Antarctica loses about 31 billion tonnes per year.

The study found that Antarctica lost much more ice to the sea than it gained from snowfall, resulting in an increase in sea level, while the Greenland ice sheet gained more ice from snowfall at high altitudes than it lost from melting ice along its coast.

A recent study by Eric Rignot of NASA’s Jet Propulsion Laboratory and University of Kansas scientist Pannir Kanagaratnam, published in Science in February, showed Greenland glaciers are melting into the sea twice as fast as previously believed.

http://it.moldova.org/stiri/eng/11010/

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New research shows that global warming might be worse than expected because of melting permafrost, permanently frozen soil, which can release the "greenhouse" gas, carbon dioxide. Computer models predict higher future temperatures when these gases are taken into consideration.


Scientists say the Earth's rising atmospheric temperatures are largely caused by human-generated emissions of heat-trapping gases, mainly carbon dioxide. But recent findings suggest that the Earth is also a culprit. It, too, gives off carbon dioxide.

That is because vast amounts of carbon are trapped in permafrost. Over the ages, this frozen ground has accumulated layers of windblown dust, roots, and other organic, or carbon-containing, matter as glaciers advanced and retreated.

As long as the permafrost remains frozen, the carbon stays in the soil. But botanist Ted Schurr of the University of Florida says higher temperatures will melt the soil, releasing greenhouse gases, which would boost temperatures even more. Schurr traveled to Siberia to collect samples of permafrost up to three meters below the surface. He reports in the journal Science that when the permafrost melted in the laboratory, microbes digested the carbon and converted it to carbon dioxide.

"It's like food in your freezer," explained Schurr. "If It's really cold, those bacteria and fungi can't do their thing. Now if you warm this soil organic matter up from below there, you unfreeze it, then they can metabolize it and convert it to carbon dioxide. This gas then goes into the atmosphere and contributes to the carbon there."

Scientists know how much carbon dioxide people put into the air each year, but until now it was not clear how much greenhouse gas the Earth could give off. Schurr found that the deposits deep in the Siberian permafrost were much greater than previously thought and could potentially double current carbon dioxide concentrations if released.

"We describe a really large pool of about 500 billion tons of carbon," said Schurr. "In comparison, the atmosphere right now has about 730 billion tons. So we are talking about almost as much carbon stored in permafrost in Siberia as there is in the atmosphere now. "

In another study in the journal Geophysical Research Letters, Margaret Torn at the University of California at Berkeley shows the climate impact of this additional greenhouse factor. "We found a significant amount of warming coming back from these feedbacks that we're not yet estimating," said Torn. "The Intergovernmental Panel on Climate Change, or IPCC, currently estimates that we could have warming by as much as 5.8 degrees Celsius by the end of the 21st century. But if Earth responds as it has in the past, we would actually be committed to 7.7 degrees Celsius warming."

These latest studies are only steps toward a complete understanding of the atmosphere's complex nature. Scientists are still struggling to incorporate other greenhouse factors such as clouds, dust, and pollutants into their analysis. Torn says as more is known about them, they will be used to refine current climate models.

Courtesy: http://www.voanews.com/english/2006-08-07-voa72.cfm