New Envisat images highlight the dramatic retreat of the Aral Sea’s shoreline.

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ScienceDaily (July 12, 2009) — New Envisat images highlight the dramatic retreat of the Aral Sea’s shoreline from 2006 to 2009. The Aral Sea was once the world’s fourth-largest inland body of water, but it has been steadily shrinking over the past 50 years since the rivers that fed it were diverted for irrigation projects.

By the end of the 1980s, it had split into the Small Aral Sea (north), located in Kazakhstan, and the horse-shoe shaped Large Aral Sea (south), shared by Kazakhstan and Uzbekistan.
By 2000, the Large Aral Sea had split into two – an eastern and western lobe. As visible in the images, the eastern lobe retreated substantially between 2006 and 2009. It appears to have lost about 80% of its water since the 2006 acquisition, at which time the eastern lobe had a length of about 150 km and a width of about 70 km.
The sea’s entire southern section is expected to dry out completely by 2020, but efforts are underway to save the northern part.
The Kok-Aral dike, a joint project of the World Bank and the Kazakhstan government, was constructed between the northern and southern sections of the sea to prevent water flowing into the southern section. Since its completion in 2005, the water level has risen in the northern section by an average of 4 m.
As the Aral Sea evaporated, it left behind a 40 000 sq km zone of dry, white salt terrain now called the Aral Karakum Desert. Each year violent sandstorms pick up at least 150 000 tonnes of salt and sand from the Aral Karakum and transport it across hundreds of km, causing severe health problems for the local population and making regional winters colder and summers hotter. In an attempt to mitigate these effects, vegetation that thrives in dry, saline conditions is being planted in the former seabed.
In 2007, the Kazakhstan government secured another loan from the World Bank to implement the second stage, which includes the building of a second dam, of the project aimed at reversing this man-made environmental disaster.
Envisat acquired these images on 1 July 2006 and 6 July 2009 with its Medium Resolution Imaging Spectrometer (MERIS) instrument while working in Full Resolution Mode to provide a spatial resolution of 300 m.
Adapted from materials provided by European Space Agency.

Beyond Carbon Dioxide: Growing Importance Of Hydrofluorocarbons (HFCs) In Climate Warming

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ScienceDaily (July 9, 2009) — Some of the substances that are helping to avert the destruction of the ozone layer could increasingly contribute to climate warming, according to scientists from NOAA's Earth System Research Laboratory and their colleagues in a new study in the journal Proceedings of the National Academy of Sciences.

The authors took a fresh look at how the global use of hydrofluorocarbons (HFCs) is expected to grow in coming decades. Using updated usage estimates and looking farther ahead than past projections (to the year 2050), they found that HFCs—especially from developing countries—will become an increasingly larger factor in future climate warming.
"HFCs are good for protecting the ozone layer, but they are not climate friendly," said David W. Fahey, a scientist at NOAA and second author of the new study. "Our research shows that their effect on climate could become significantly larger than we expected, if we continue along a business-as-usual path."
HFCs currently have a climate change contribution that is small (less than 1 percent) in comparison to the contribution of carbon dioxide (CO2) emissions. The authors have shown that by 2050 the HFCs contribution could rise to 7 to 12 percent of what CO2 contributes. And if international efforts succeed in stabilizing CO2 emissions, the relative climate contribution from HFCs would increase further.
HFCs, which do not contain ozone-destroying chlorine or bromine atoms, are used as substitutes for ozone-depleting compounds such as chlorofluorocarbons (CFCs) in such uses as refrigeration, air conditioning, and the production of insulating foams. The Montreal Protocol, a 1987 international agreement, has gradually phased out the use of CFCs and other ozone-depleting substances, leading to the development of long-term replacements such as HFCs.
Though the HFCs do not deplete the ozone layer, they are potent greenhouse gases. Molecule for molecule, all HFCs are more potent warming agents than CO2 and some are thousands of times more effective. HFCs are in the "basket of gases" regulated under the 1997 Kyoto Protocol, an international treaty to reduce emissions of greenhouse gases.
The new study factored in the expected growth in demand for air conditioning, refrigerants, and other technology in developed and developing countries. The Montreal Protocol's gradual phasing out of the consumption of ozone-depleting substances in developing countries after 2012, along with the complete phase-out in developed countries in 2020, are other factors that will lead to increased usage of HFCs and other alternatives.
Decision-makers in Europe and the United States have begun to consider possible steps to limit the potential climate consequences of HFCs. The PNAS study examined several hypothetical scenarios to mitigate HFC consumption. For example, a global consumption limit followed by a 4 percent annual reduction would cause HFC-induced climate forcing to peak in the year 2040 and then begin to decrease before the year 2050.
"While unrestrained growth of HFC use could lead to significant climate implications by 2050, we have shown some examples of global limits that can effectively reduce the HFCs' impact," said John S. Daniel, a NOAA coauthor of the study.
The authors of the PNAS study are Guus J.M Velders of the Netherlands Environmental Assessment Agency, Fahey and Daniel of NOAA's Earth System Research Laboratory, Mack McFarland of DuPont Fluoroproducts, and Stephen O. Andersen of the U.S. Environmental Protection Agency.
Journal reference:
. The large contribution of projected HFC emissions to future climate forcing. Proceedings of the National Academy of Sciences, June 22, 2009
Adapted from materials provided by National Oceanic and Atmospheric Administration.

Ice Volume Of Switzerland’s Glaciers Calculated

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ScienceDaily (July 9, 2009) — Swiss glaciers have lost a lot of ice in recent years due to increased melting. As temperatures climb, so do the fears that the glaciers could one day disappear altogether. Until now it could only be estimated approximately how big the ice volume in the Swiss Alps actually is and how it has changed in recent years.

A team of scientists headed by Martin Funk, ETH-Professor at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) at ETH Zurich, however, has now developed a novel procedure for determining the ice volume of a glacier. Their results are presented in the current issue of Global and Planetary Change.
The researchers developed the new method according to the law of mass conservation, which states that the surface mass balance has to be balanced by the ice flow and the change in ice thickness. This allows to infer on the ice thickness distribution of a glacier from the surface topography by estimating the mass balance distribution. "The calculation of the current ice volume is the most important indicator in predicting future glacier changes," explains Martin Funk.
74 km3 of glaciers
The scientists applied the procedure to the 59 Swiss glaciers larger than three square kilometers. For the remaining 1’400 glaciers, the ice volume was estimated by using an empirical area-volume approach derived from the new generated data set. The total glacier ice volume in 1999 was estimated to 74 km3, with an accuracy of 9 km3. This means the total volume of all glaciers of Switzerland is smaller than that of the Lake Geneva, which has a water volume of 89 km3. With a glaciated land area of 1’063 km2, the Swiss glaciers have an average ice thickness of 70 meters.
The scientists also discovered that the 59 larger glaciers account for almost 88% of the ice volume, whereas about 24% is stored in the Aletsch region alone (the Oberaletschgletscher, Mittelaletschgletscher and Grosser Aletschgletscher). The area of the Great Aletsch Glacier is approximately the same as the total area of all the Swiss glaciers smaller than one square kilometer. However, they have an overall ice volume that is twenty times smaller than that of the Grosser Aletschgletscher. "This just goes to show that the large glaciers carry the most weight in determining a region’s ice volume," explains Funk.
Volume decreased by 12 percent
The ETH Zurich study also revealed a change in the ice volume since 1999. Over the last decade – the warmest for 150 years – Switzerland’s glaciers have lost 9 km3 of ice (-12%), including 2.6 km³ (-3.5%) in the record-breaking sum-mer of 2003 alone. These figures are all the more alarming as the climate continues to warm up and the temperatures in the Swiss Alps are expected to increase by 1.8 degrees in the winter and 2.7 degrees in the summer by 2050.
Adapted from materials provided by ETH Zurich.

Close Relationship Between Past Warming And Sea-level Rise

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ScienceDaily (July 7, 2009) — A team from the National Oceanography Centre, Southampton (NOCS), along with colleagues from Tübingen (Germany) and Bristol presents a novel continuous reconstruction of sea level fluctuations over the last 520 thousand years. Comparison of this record with data on global climate and carbon dioxide (CO2) levels from Antarctic ice cores suggests that even stabilisation at today's CO2 levels may commit us to sea-level rise over the next couple of millennia, to a level much higher than long-term projections from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC).

Little is known about the total amount of possible sea-level rise in equilibrium with a given amount of global warming. This is because the melting of ice sheets is slow, even when temperature rises rapidly. As a consequence, current predictions of sea-level rise for the next century consider only the amount of ice sheet melt that will occur until that time. The total amount of ice sheet melting that will occur over millennia, given the current climate trends, remains poorly understood.
The new record reveals a systematic equilibrium relationship between global temperature and CO2 concentrations and sea-level changes over the last five glacial cycles. Projection of this relationship to today's CO2 concentrations results in a sea-level at 25 (±5) metres above the present. This is in close agreement with independent sea-level data from the Middle Pliocene epoch, 3-3.5 million years ago, when atmospheric CO2 concentrations were similar to the present-day value. This suggests that the identified relationship accurately records the fundamental long-term equilibrium behaviour of the climate system over the last 3.5 Million years.
Lead author Professor Eelco Rohling of the University of Southampton's School of Ocean and Earth Science based at NOCS, said: "Let's assume that our observed natural relationship between CO2 and temperature, and sea level, offers a reasonable 'model' for a future with sustained global warming. Then our result gives a statistically sound expectation of a potential total long-term sea-level rise. Even if we would curb all CO2 emissions today, and stabilise at the modern level (387 parts per million by volume), then our natural relationship suggests that sea level would continue to rise to about 25 m above the present. That is, it would rise to a level similar to that measured for the Middle Pliocene."
Project partners Professor Michal Kucera (University of Tübingen) and Dr Mark Siddall (University of Bristol), add: "We emphasise that such equilibration of sea level would take several thousands of years. But one still has to worry about the large difference between the inferred high equilibrium sea level and the level where sea level actually stands today. Recent geological history shows that times with similarly strong disequilibria commonly saw pulses of very rapid sea-level adjustment, at rates of 1-2 metres per century or higher."
The new study's projection of long-term sea-level change, based on the natural relationship of the last 0.5 to 3.5 million years, differs considerably from the IPCC's model-based long-term projection of +7 m. The discrepancy cannot be easily explained, and new work is needed to ensure that the 'gap is closed'.
The observed relationships from the recent geological past can form a test-bed or reality-check for models, to help them achieve improved future projections.
The project was funded by the Natural Environment Research Council (UK) and the Deutsche Forschungs-Gemeinschaft (Germany).
The authors are Eelco Rohling (NOCS), Katharine Grant (NOCS), Mike Bolshaw (NOCS), Andrew Roberts (NOCS), Mark Siddall (University of Bristol), Christoph Hemleben (University of Tübingen) and Michal Kucera (University of Tübingen).
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Journal reference:
Rohling et al. Antarctic temperature and global sea level closely coupled over the past five glacial cycles. Nature Geoscience, June 21, 2009; DOI: 10.1038/ngeo557
Adapted from materials provided by National Oceanography Centre, Southampton (UK).

Natural Deep Earth Pump Fuels Earthquakes And Ore

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ScienceDaily (July 6, 2009) — For the first time scientists have discovered the presence of a natural deep earth pump that is a crucial element in the formation of ore deposits and earthquakes.

The process, called creep cavitation, involves fluid being pumped through pores in deformed rock in mid-crustal sheer zones, which are approximately 15 km below the Earth's surface.
The fluid transfer through the middle crust also plays a key role in tectonic plate movement and mantle degassing.
The discovery was made by examining one millimetre sized cubes of exposed rock in Alice Springs, which was deformed around 320 million years ago during a period of natural mountain formation.
The evidence is described in a paper published in the latest edition of Nature entitled Creep cavitation can establish a dynamic granular fluid pump in ductile shear zones.
One of the paper's author's CSIRO Exploration and Mining scientist Dr Rob Hough said that this was the first direct observation of fluids moving through the mid-crustal shear zone.
"We are seeing the direct evidence for one of the processes that got ore forming fluids moving up from the mantle to the shallow crust to form the ore deposits we mine today, it is also one of the mechanisms that can lead to earthquakes in the middle crust," Dr Hough said.
Research leader Dr Florian Fusseis, from the University of Western Australia, said that the discovery could provide valuable information in understanding how earthquakes are formed.
"While we understand reasonably well why earthquakes happen in general, due to stress build-up caused by motions of tectonic plates, the triggering of earthquakes is much more complex," Dr Fusseis said.
"To understand the 'where' and 'when' of earthquakes, the 'how' needs to be understood first. We know that earthquakes nucleate by failure on a small part of a shear zone."
Dr Fusseis said that while their sample did not record an earthquake it gave them an insight into the structures that could be very small and localized precursors of seismic failure planes.
The discovery was made possible through the use of high-resolution Synchrotron X-ray tomographic, scanning electron microscope observations at the nanoscale and advanced visualisation using iVEC in Western Australia.
The authors of the paper propose that the fluid movement, described as the granular fluid pump, is a self sustaining process where pores open and close allowing fluid and gas to be pumped out.
The paper was written by five authors from CSIRO Exploration and Mining working through the Minerals Down Under National Research Flagship, The School of Earth & Environmental Sciences, University of Western Australia and Advanced Photon Source, and Argonne National Laboratory, USA.
Three of the authors are with CSIRO: Prof Klaus Regenauer-Lieb who shares his time between CSIRO and the University of Western Australia and is also a WA Premiers Fellow; Dr Jie Liu and Dr Rob Hough.
The experiments at the Advanced Photon Source in Chicago were funded in part by the Australian Synchrotron Research Program.
Adapted from materials provided by CSIRO Australia.

World's Largest Aerosol Sensing Network Has Leafy Origins

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ScienceDaily (July 6, 2009) — Twenty years ago, Brent Holben was part of a NASA team studying vegetation from space. In an unlikely career twist, his research morphed into the study of a critical, if overlooked, subplot in the story of climate change.

From his office at NASA's Goddard Space Flight Center in Greenbelt, Md., Holben helps manage the world's largest network of ground-based sensors for aerosols -- tiny specks of solids and liquids that waft about in the atmosphere. These particles come from both human and natural sources and can be observed everywhere in the world.
Scientists know that some of them play an outsized role in Earth's climate. And much of that knowledge has come from the Aerosol Robotic Network, or AERONET, the collaborative, international sensor network which Holben leads.
"Aerosols play a key role in climate, and pretty much everybody who studies aerosols uses data from AERONET," said William Lau, director of the Atmospheric Sciences Division at Goddard. "Without AERONET, our understanding of the climate system simply wouldn't be where it is today."
Trouble Seeing the Forest and the Trees
The origins of AERONET date to the late 1980s, when Goddard researchers were attempting — and struggling — to study vegetation using satellites. "The atmosphere kept getting in the way," Holben said. Satellites couldn't properly sense the vegetation through all the dust, minerals, soot, salt, and other atmospheric aerosols obscuring the view. The problem prompted Holben to put his vegetation research aside "temporarily" to tackle aerosols. In 1992, he planned a field campaign to the Amazon, where farmers were burning swaths of rainforest to clear the land. The heavy emissions from the fires made it an ideal environment to study aerosol particles. During that project, Holben began to develop a method for studying aerosols that became a template for future campaigns. He used lamp-sized instruments called sun-sky photometers to measure the intensity of light filtering through a given column of atmosphere. Aerosol particles scatter or absorb portions of the incoming light, allowing scientists to deduce their size, shape, and chemical composition. Often the instruments are installed on the roofs of universities, but solar-powered versions of the devices can also be deployed in remote corners of the world, far off the grid.
Intriguing results began to emerge from the Amazon campaign as well as others in Africa, Canada, and Hawaii. Though aerosols generally reside in the atmosphere for just a few weeks, the data from the Amazon showed that heavy fires could increase pollution levels dramatically for as long as two months after the burning season ended.
A Time to Plant, A Time to Reap
The timing of Holben's foray into aerosol research turned out to be impeccable. Around the time he was deploying photometers in the Amazon, the volcanic eruption of Mount Pinatubo in the Philippines flooded the atmosphere with sulfate aerosols. The burst blocked some solar radiation from reaching Earth's surface and caused global temperatures to drop by 0.5 °C (0.9 °F) for a few years. The eruption underscored the profound impact sulfate aerosols could have on climate. It also reminded researchers how poorly they understood many other types of aerosols. Deploying more photometers was a logical and relatively low-cost way to start filling the gaps in knowledge. Holben and colleagues slowly set up an array of sensors in the United States, while forging collaborations for similar networks in France, Brazil, Spain, Canada, and Japan. Soon, Holben and his collaborators realized that they had created a global network. In 1998, he described the network's potential in an article in Remote Sensing of Environment, laying out methods of calibrating the sensors and guidelines for collecting and interpreting data. With that paper, AERONET was officially born. Today AERONET consists of approximately 400 sites in 50 countries on all seven continents. There are AERONET stations on remote sand dunes in Mali, on the ice sheet at South Pole, and on the tiny island nation of Nauru in the South Pacific.
An Ever-Wider Net
By providing accurate measurements from the ground, AERONET has emerged as the best tool to validate the accuracy of new satellite instruments. For example, scientists have relied upon AERONET to reconcile differences between aerosol measurements from the Moderate-Resolution Imaging Spectroradiometer (MODIS) and the Multiangle Imaging SpectroRadiometer (MISR), two instruments on NASA's Terra satellite. "Without AERONET, we'd have no baseline for comparison," said Michael Mishchenko, a remote sensing expert at NASA's Goddard Institute for Space Studies in New York City and project scientist for NASA's upcoming Glory mission. Glory will rely on AERONET to validate the Aerosol Polarimetery Sensor, an innovative instrument that will distinguish between different types of aerosols from space. Though developed nations are dense with AERONET stations, coverage in many developing areas remains sparse. That's a problem because aerosols don't recognize borders and they aren't limited to land masses.
Gaps in coverage can lead to gaps in understanding, said Venkatachalam Ramaswamy, director of the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory and a professor of geosciences at Princeton University, N.J. Compared to other factors that affect climate — such as the output of the Sun or greenhouse gases — aerosols are considered the least-well understood. So Holben and colleagues are working to expand AERONET and continue filling in the gaps. Zhanqing Li, an atmospheric scientist at the University of Maryland, College Park, Md. is leading an international field campaign in China, where aerosol loading is exceptionally high. The scientists are deploying AERONET photometers and other instruments that gather information about the impact of aerosols on the region's climate, especially on the dynamics of the Asian monsoon.
In India, AERONET-affiliated researchers are deploying sensors along the flight track of NASA's CALIPSO satellite, which uses light detection and ranging (LIDAR) to measure aerosols. AERONET's open-source approach to data collection and analysis has also aided its expansion. All data is relayed through weather satellites to a centralized database at Goddard, where it quickly becomes available on the Internet.
"It's always been important to me that AERONET data be freely available," Holben said. "The taxpayers fund this project, and they deserve to know what we're finding."
"Scientists are typically protective of their data, so Holben's insistence on data sharing was a bit avant-garde," said Joel Schafer, a Goddard AERONET scientist. The strategy has paid off. The 1998 study Holben used to introduce AERONET recently passed an impressive academic milestone: it has been cited more than 1,000 times, making it one of the most referenced papers in contemporary earth science. With that accomplishment under his belt, perhaps Holben will have the time to turn back to that old vegetation research.
Adapted from materials provided by NASA/Goddard Space Flight Center. Original article written by Adam Voiland.

Desert Dust Alters Ecology Of Colorado Alpine Meadows

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ScienceDaily (July 5, 2009) — Accelerated snowmelt--precipitated by desert dust blowing into the mountains--changes how alpine plants respond to seasonal climate cues that regulate their life cycles, according to results of a new study reported this week in the journal Proceedings of the National Academy of Sciences (PNAS). These results indicate that global warming may have a greater influence on plants' annual growth cycles than previously thought.

Current mountain dust levels are five times greater than they were before the mid-19th century, due in large part to increased human activity in deserts.
"Human use of desert landscapes is linked to the life cycles of mountain plants, and changes the environmental cues that determine when alpine meadows will be in bloom, possibly increasing plants' sensitivity to global warming," said Jay Fein, program director in the National Science Foundation (NSF)'s Division of Atmospheric Sciences, which funded the research in part.
This year, 12 dust storms have painted the mountain snowpack red and advanced the retreat of snow cover, likely by more than a month across Colorado.
"Desert dust is synchronizing plant growth and flowering across the alpine zone," said Heidi Steltzer, a Colorado State University scientist who led the study. "Synchronized growth was unexpected, and may have adverse effects on plants, water quality and wildlife."
"It's striking how different the landscape looks as result of this desert-and-mountain interaction," said Chris Landry, director of the Center for Snow and Avalanche Studies (CSAS) in Silverton, Colo., who, along with Tom Painter, director of the Snow Optics Laboratory at the University of Utah, contributed to the study.
"Visitors to the mountains arriving in late June will see little remaining snow," said Landry, "even though snow cover was extensive and deep in April. The snow that remains will be barely distinguishable from the surrounding soils.
Earlier snowmelt by desert dust, said Painter, "depletes the natural water reservoirs of mountain snowpacks and in turn affects the delivery of water to urban and agricultural areas."
With climate change, warming and drying of the desert southwest are likely to result in even greater dust accumulation in the mountains.
In an alpine basin in the San Juan Mountains, the researchers simulated dust effects on snowmelt in experimental plots. They measured dust's acceleration of snowmelt on the life cycles of alpine plants.
The timing of snowmelt signals to mountain plants that it's time to start growing and flowering. When dust causes early snowmelt, plant growth does not necessarily begin soon after the snow is gone.
Instead, plants delay their life cycle until air temperatures have warmed consistently above freezing.
"Climate warming could therefore have a great effect on the timing of growth and flowering," said Steltzer.
Competition for water and nutrient resources among plants should increase, leading to the loss of less competitive species. Delayed plant growth could increase nutrient losses, decreasing water quality.
Similarity in flowering times and plant growth will result in abundant resources for wildlife for a short time rather than staggered resources over the whole summer, Steltzer believes.
"With increasing dust deposition from drying and warming in the deserts," she said, "the composition of alpine meadows could change as some species increase in abundance, while others are lost, possibly forever."
Adapted from materials provided by National Science Foundation.