Climate: Last summer’s Greenland ice sheet surface meltdown linked with an unusual kink in the jet stream

Posted on June 18, 2013 by Bob Berwyn

July 2012 melt event far surpassed previous record

In the images above, areas classified as “probable melt” (light pink) correspond to sites where at least one satellite detected surface melting. Areas classified as “melt” (dark pink) correspond to sites where two or three satellites detected melting.

In the images above, areas classified as “probable melt” (light pink) correspond to sites where at least one satellite detected surface melting. Areas classified as “melt” (dark pink) correspond to sites where two or three satellites detected melting.

By Summit Voice

SUMMIT COUNTY — Along with an unusual constellation of low clouds, changes the jet stream were also a factor in last summer’s exceptional surface melt of the Greenland Ice Sheet, according to a research team led by the University of Sheffield’s geography professor Edward Hanna.

A NOAA study published in March indicated that a lingering layer of thin, low clouds helped intensify atmospheric conditions leading to the meltdown.

Hanna and his colleagues used a computer model simulation (called SnowModel) and satellite data to confirm that last summer’s meltdown was unprecedented in the past 50 years. About 90 percent of the ice-sheet surface melted July 11, far surpassing the previous known surface melt extent record of 52 percent in 2010. (more…)

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Can air pollution shift rain bands and cause drought?

Posted on June 9, 2013 by Bob Berwyn
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Lake Chad in 2001 is just a fraction of its normal size, surround by the drylands of the Sahel region in this NASA Earth Observatory image acquired by the MODIS satellite.

Research suggests far-reaching link between industrial emissions and climate

By Summit Voice

FRISCO — A decades-long drought in central Africa may have been caused by air pollution from industrial sources in the northern hemisphere. The drought peaked in the mid-1980s, as Lake Chad nearly dried up and researchers initially pointed to over-grazing and poor agricultural practices as the main cause.

But new research from the University of Washington suggests that aerosols emanating from coal-burning factories in the United States and Europe during the 1960s, ’70s and ’80s cooled the entire Northern Hemisphere, shifting tropical rain bands south of their average position. (more…)

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Global warming: Study helps quantify how much Alaska’s melting glaciers contribute to sea level rise

Posted on May 24, 2013 by Bob Berwyn

Research aims to fine-tune sea-level rise projections

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The Columbia Glacier in Alaska is one of the most rapidly changing glaciers in the world. Visit this NASA Earth Observatory web page for more information.

By Summit Voice

SUMMIT COUNTY — As part of a global study of melting glaciers and rising sea level, two University of Alaska Fairbanks geophysicists helped compile a global inventory of glaciers, with a focus on Alaska.

Before the study, only about 40 percent of Alaska’s glaciers were inventoried. The two researchers, Anthony Arendt and Regine Hock, concluded that Alaska remains one of the top contributors to global sea level. (more…)

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EU ice2sea report offers new estimates of sea level rise

Posted on May 16, 2013 by Bob Berwyn
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The EU’s ice2sea program helps to determine potential future impacts of rising sea levels.

Research focuses on contribution of melting glaciers, ice caps and ice shelves

By Summit Voice

FRISCO — After four years of studies and more than 150 peer-reviewed papers, The EU-funded ice2sea program has concluded that melting ice may not contribute as much to sea level rise as some other studies have suggested.

Under a moderate greenhouse gas emissions scenario, the contribution from continental ice will likely amount to between 3.5 and 36.8 centimeters (1.4 to 14.5 inches) by 2100, the program’s leaders said this week, unveiling a new report that summarizes their research. The report is online at the ice2sea home page.

Some of the ice2sea studies have:

The new report includes several case studies outlining the impacts of sea level rise to specific areas, including economically valuable developed areas like the port of Rotterdam and the Thames Estuary, as well as natural areas with unique natural values, like the Machair ecosystems in Ireland and Scotland that thrive in a delicate balance of land and sea. (more…)

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Global warming: Mt. Everest’s glaciers melting away

Posted on May 15, 2013 by Bob Berwyn

Temperatures up, precipitation down in key Asian watersheds

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A new study finds a decline in snow and ice on Mount Everest (second peak from left) and the national park surrounding it. Photo courtesy Pavel Novak.

FRISCO — Even at the frozen roof of the world in the mighty Himalaya, global warming is evident.

The snow line in the Mt. Everest region has moved uphill by 180 meters (590 feet). Glaciers in the region are shrinking, some by as much as 13 percent in the past 50 years, and precipitation has declined, according to a team of scientists who will present their findings this week at the Meeting of the Americas in Cancún, Mexico.

Glaciers smaller than one square kilometer are disappearing the fastest and have experienced a 43 percent decrease in surface area since the 1960s, according to Sudeep Thakuri, who is leading the research as part of his PhD graduate studies at the University of Milan in Italy. Based on the detailed measurements of satellite images, the pace of melting speeding up, Thakuri said. (more…)

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Climate: New study helps illustrate how CO2 affects Arctic

Posted on May 12, 2013 by Bob Berwyn
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A new study suggests the Earth’s climate system is more sensitive to CO2 changes than assumed by the IPCC’s 2007 global climate report.

Researchers establish longest regional climate record using sediment cores from an Arctic Lake that’s been undisturbed for 3.6 million years

By Summit Voice

FRISCO — Sediment cores from a crater lake in Siberia are helping scientists understand how varying concentrations of atmospheric carbon dioxide affect the Arctic climate.

The sediment cores help establish the longest continuous climate record from the region, showing that the Arctic was a very warm place during a period about 3.5 to 2 million years ago, when CO2 levels were similar to today’s.

The research leads to the conclusion that even small fluctuations in CO2 can result in big changes in the Arctic, according to Julie Brigham-Grette, of the University of Massachusetts Amherst.

The study indicates Arctic may have been much warmer during that era than other climate studies suggest, and that the planet’s climate system is probably more sensitive to CO2 levels than assumed in the 2007 report of the Intergovernmental Panel on Climate Change. (more…)

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Global warming: Andes glacier melt to affect water supplies

Posted on January 23, 2013 by Bob Berwyn

New study tracks rapidly accelerating rate of ice decline since 1950s

The Perito Moreno Glacier is one of the largest in Patagonia at 30 kilometers long. The glacier descends from the Southern Patagonian Icefield (image top)—2100 meters elevation (6825 feet) in the Andes Mountains—down into the water and warmer altitudes of Lago Argentino at 180 meters above sea level.

The Perito Moreno Glacier is one of the largest in Patagonia at 30 kilometers long. The glacier descends from the Southern Patagonian Icefield (image top)—2100 meters elevation (6825 feet) in the Andes Mountains—down into the water and warmer altitudes of Lago Argentino at 180 meters above sea level. Satellite image courtesy NASA Earth Observatory.

By Summit Voice

SUMMIT COUNTY — Glaciers in large parts of the Andes have shrunk on average by 30 to 50 percent since the 1970s, and the unprecedented retreat could soon begin to affect water supplies for Andean communities.

Temperatures in the region have warmed by more than 1 degree Fahrenheit in the past few decades, said Antoine Rabatel, a researcher at the Laboratory for Glaciology and Environmental Geophysics in Grenoble, France, and lead author of a recent study on the glaciers in the region.

Globally, glaciers have been retreating at a moderate pace as the planet warmed after the peak of the Little Ice Age, a cold period lasting from the 16th to the mid-19th century. Over the past few decades, however, the rate of melting has increased steeply in the tropical Andes, at a pace not seen for at least the last 300 years. (more…)

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Global warming: At current CO2 concentrations, sea level set to rise about 30 feet during the next few centuries

Posted on January 3, 2013 by Bob Berwyn
Concentrations of atmospheric carbon dioxide at Mauna Loa, Hawaii.

Average carbon dioxide levels will probably start to stay above 400 ppm sometime in 2013.

Analysis of 40-million year record calibrates CO2 concentrations with historic sea levels

By Summit Voice

SUMMIT COUNTY — Even if  atmospheric carbon dioxide concentrations were to be stabilzed at today’s levels of about 400 parts per million, sea levels would gradually increase by about 30 during the next few centuries, according to researchers who calibrated CO2 levels against sea level for the past 40 million years.

The study sought to pinpoint the ‘natural equilibrium’ sea level for CO2 concentrations ranging between ice-age values of 180 parts per million and ice-free values of more than 1,000 parts per million. (more…)

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Global warming research eyes ‘runaway’ ice melt

Posted on December 31, 2012 by Bob Berwyn

Sea level forecasts may be way off

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Will there be runaway ice sheet melting? Bob Berwyn photo.

By Summit Voice

FRISCO — Most climate models are probably underestimating the rate of sea level rise expected during the next few decades, according to some of the latest research that tries to quantify how much ice may melt off the Greenland and Antarctica ice sheets.

A Dec. 26 update by James Hansen and Makiko Sato warns that melting of those ice sheets could increase sea level rise exponentially higher than most existing forecasts, potentially inundating coastal cities around the world with several feet of water by the end of the century.

The short paper discusses the linearity assumptions in most existing climate models and suggests that, if greenhouse gas emissions continue unchecked, “the climate forcing will be so large that non-linear ice sheet disintegration should be expected and multi- meter sea level rise not only possible but likely.” (more…)

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Study: Colorado River flows could decline by 10 percent as rainfall patterns shift and temperatures rise in the Southwest

Posted on December 30, 2012 by Bob Berwyn

Water managers must plan for a drier future

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Dillon Reservoir, a key water supply for Denver, may see many more days with low water levels in the next few decades, according to recent studies. Bob Berwyn photo.

By Summit Voice

FRISCO — Just a few weeks after the U.S. Bureau of Reclamation released a major report on the future of the Colorado, a new study in the journal Nature Climate Change reinforced some of the federal government findings, predicting a 10 percent drop in Colorado River flows during the next few decades.

That may not sound like much, but it’s enough to disrupt longtime water-sharing agreements between farms and cities across the American Southwest, from Denver to Los Angeles to Tucson, and through California’s Imperial Valley, according to the researchers from Columbia University’s Lamont-Doherty Earth Observatory. (more…)

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