Greenhouse gas warming overrides all other climate signals

Posted on April 23, 2013 by Bob Berwyn

Late 20th century temperature spike reversed long cooling trend

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New study finds that Europe’s 2003 heatwave brought the hottest temperatures in 2000 years.

By Summit Voice

SUMMIT COUNTY — Heat-trapping greenhouse gases have driven global temperatures higher than at any other time during the past 1,400 years, according to a new study covering all seven continents. The big spike between 1971 and 2000 reversed a natural cooling trend that had lasted several hundred years, according to climate data from tree rings, pollen, cave formations, ice cores, lake and ocean sediments, and historical records from around the world.

“This paper tells us what we already knew, except in a better, more comprehensive fashion,” said study co-author Edward Cook, a tree-ring scientist at Lamont-Doherty Earth Observatory who led the Asia reconstruction. (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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Climate: Some regions see more flooding during cooling regimes

Posted on October 19, 2012 by Bob Berwyn

Study in Alpine lakes traces 1,600-year of history climate change

Sediments in Austria’s Mondsee show more evidence of flooding during transitions to cooler climate phases.

By Summit Voice

SUMMIT COUNTY — While many recent research projects have highlighted the potential for more extreme weather as the planet warms up, a new study from the GFZ German Research Centre for Geosciences indicates that parts of the Alps saw more extreme flooding during periods of transition to cooler climatic conditions.

By studying sediment layers in the Mondsee, an Alpine lake near Salzburg, Austria, the researchers found evidence of flooding during the time of the Great Migration and the Early Middle Ages (AD 450-750), as well as the transition to the Little Ice Age (AD 1140-1520). In contrast, there was less flooding during the medieval warm phase (AD 1000-1140) and the coldest period of the Little Ice Age (AD 1600-1700). (more…)

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Global warming: Arctic temps out of synch with natural cycles

Posted on October 1, 2012 by Bob Berwyn

Paleo-climate data suggests region should be cooling, but greenhouse gas forcing has overpowered nature pattern

New research shows that the Arctic reversed a long-term cooling trend and began warming rapidly in recent decades. The blue line shows estimates of Arctic temperatures over the last 2,000 years, based on proxy records from lake sediments, ice cores and tree rings. The green line shows the long-term cooling trend. The red line shows the recent warming based on actual observations. Courtesy Science, modified by UCAR.

By Summit Voice

SUMMIT COUNTY — Without ever-increasing concentrations of heat-trapping greenhouse gases in the atmosphere, the Arctic would gradually be cooling instead of experiencing the rapid warming that’s been documented in the past few decades.

The long-term cooling trend, documented back to at least 2,000 years ago, is related to wobbles in the Earth’s orbit that have reduced the intensity of sunlight reaching the Arctic in summertime, when Earth is farther from the Sun, according to a recent study led by scientists from Northern Arizona University and the National Center for Atmospheric Research.

But in the middle of the 20th century, the gradual cooling ended abruptly, replaced by a sharp increase in Arctic temperatures — even though orbital cycles would suggest a continued cooling trend. The research, based on geologic records and computer models, strongly suggests that the heat-trapping effects of greenhouse gases are overpowering natural climate cycles. (more…)

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Global warming to disrupt Arctic species migration

Posted on September 16, 2012 by Bob Berwyn

Arctic foxes. Photo courtesy Yvonne Cox.

Study shows impacts to Arcit fox populations

By Summit Voice

FRISCO — It’s very likely that human-caused global warming will disrupt the natural cycles of glaciation that have prevailed in recent millennia, and that could spell trouble for species that have relied on bridges of sea ice to maintain genetic diversity.

That includes Arctic foxes that were able to colonize Iceland during the Little Ice, according to research by scientists at the UK’s Durham University, who said that Arctic foxes were able to migrate to Iceland from Russia, North America and Greenland when such a bridge formed, between 200 and 500 years ago.

Iceland’s population of about 10,000 arctic foxes is not at risk, the researchers said, but explained that increasing isolation from the rest of the Arctic, caused by warmer temperatures and a lack of sea ice, could further differentiate the island’s population from their mainland relatives. (more…)

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Study suggests Southwest fires driven by year-to-year weather cycles rather than long-term climate variations

Posted on May 17, 2012 by Bob Berwyn

A low-intensity ground fire burns through ponderosa pine during a prescribed fire in Grand Canyon National Park. PHOTO COURTESY NATIONAL PARK SERVICE.

New study offers more evidence that historical fire suppression is the main contributing factor in today’s big southwestern fires

By Summit Voice

SUMMIT COUNTY — A detailed analysis of historic fire-scar records and tree-ring data going back centuries offers more evidence that recent mega-fires in the Southwest are unprecedented and likely a result of widespread fire suppression.

While many of today’s southwestern forests haven’t seen a fire in more than 100 years, historical records show that, in the pre-suppression era, they rarely went as long as 40 or 50 years without a low-intensity ground fire.

To reach their conclusions, researchers at Southern Methodist University used a statistical model that encompassed 1,500 years of climate and fire patterns. They wanted to test if today’s dry, hot climate alone is causing the megafires that routinely destroy millions of acres of forest. (more…)

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West: Wildfire regimes out of synch with climate cycles

Posted on February 15, 2012 by Bob Berwyn

‘Policies of fire suppression that do not account for this unusual environmental situation are unsustainable.’

One of the many wildfires that burned during a record fire season in Texas. PHOTO COURTESY TEXAS FOREST SERVICE/INCIWEB.

By Summit Voice

SUMMIT COUNTY —After a careful comparison of historic fire frequency and climate records (based in part on an extensive charcoal database) a team of university researchers concluded that human activity reduced the frequency of wildfires from the 1,000-year maximum to the 1,000-year minimum — in less than 100 years, leading to a fire deficit.

In short, fire regimes are out of whack with climate cycles. A combination of drought, a build-up of combustible fuels and increased tree mortality is the recipe for a “perfect storm” of wildfire conditions, the researchers warned in a Feb. 14 paper published in Proceedings of the National Academy of Sciences.

The long-term perspectives gained through these studies demonstrate how strongly climate and people affect the present-day landscapes and forests of the American West, and how they may change in the future, said  University of Oregon geography professor Patrick Bartlein, one of the paper’s authors. (more…)

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Study: Volcanoes may have triggered Little Ice Age

Posted on January 31, 2012 by Bob Berwyn

New evidence from carbon-dated plant matter and lake sediments offer clues to sudden climate changes

Eruption column at Redoubt Volcano, Alaska. PHOTO COURTESY USGS.

By Summit Voice

SUMMIT COUNTY —Carbon-dating a trove of dead plant material emerging from under the Baffin Island icecap suggests that the vegetation was frozen and engulfed during a relatively sudden event that may have triggered the start of the Little Ice Age.

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.

Evidence from the new study suggests the centuries-long span of cooling temperatures began abruptly sometime between 1275 and 1300, following a 50-year-long episode of four massive tropical volcanic eruptions. (more…)

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Research pinpoints historic Greenland climate changes

Posted on May 31, 2011 by Bob Berwyn

Greenland.

New evidence shows Norse abandoned settlements when the weather got colder

By Summit Voice

SUMMIT COUNTY — Based on archaeological evidence, researchers have long speculated that the Norse settlements on Greenland disappeared when the climate turned much colder in the North Atlantic. Now, paleo-climatologists have reconstructed a 5,600-year temperature record from lake sediments that gives an accurate picture of air temperatures where the Vikings — and their Stone Age predecessors — lived.

Core samples from Greenland’s thick ice cap and other parts of the Arctic give a broader climate picture, showing that the region has experienced significant temperatures cycles during the past 100,000 years.

“This is the first quantitative temperature record from the area they were living in,” said William D’Andrea, primary author of a paper appearing in the Proceedings of the National Academy of Sciences. “So we can say there is a definite cooling trend in the region right before the Norse disappear.” (more…)

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Vanishing Oregon glacier gives climate change clues

Posted on September 5, 2010 by Bob Berwyn

Cody Beedlow, a graduate student at Oregon State University, drills into Collier Glacier as part of long term research to monitor the increase or decrease in its size. (Photo courtesy of Oregon State University)

Collier Glacier on the Three Sisters has lost half its mass in the last 150 years

By Summit Voice

SUMMIT COUNTY — The Collier glacier on the flanks of the Three Sisters in Oregon has lost about half its total mass in the last 150 years, researchers said after returning from a detailed survey of the ice field. About 20 percent of that loss has come since the 1980s.

The Collier is one of the largest glaciers in Oregon is in a short list of about 100 glaciers world-wide that’s been extensively studied for extended periods of time. The findings in Oregon are consistent with glacial retreat all over the world and provide some of the critical data needed to help quantify the effects of global change on glacier retreat and associated sea level rise.
A research program that began last year and is continuing this summer is now finding some rocks that are being exposed to daylight for the first time in thousands of years. Some of the locations where researchers now camp would have been several hundred feet deep in ice in the 1800s. (more…)

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