Tag: Atmospheric Sciences

New coral data traces 7,000 years of El Niño history

20th century oscillations show intensification that may be linked with global warming

El Nino graphic
A NOAA graphic showing early January 2012 ocean surface temperature anomalies.

By Summit Voice

SUMMIT COUNTY — Atmospheric scientists say they’ve used coral records to trace the history of El Niño cycles going back about 7.000 years, showing that 20th century oscillations  are much stronger than those captured in the fossil record.

But the study also showed large natural variations in past ENSO strength, making it difficult to attribute the 20th century intensification of ENSO to rising carbon dioxide levels. Such large natural fluctuations in ENSO activity are also apparent in multi-century climate model simulations, but the 20th century intensification stands out as statistically significant and could be linked with global warming.

The new information will help assess the accuracy of climate model projections for 21st century climate change in the tropical Pacific. Continue reading “New coral data traces 7,000 years of El Niño history”


Global warming: Researchers find extreme melting of Greenland ice cap even without record temperatures

Marco Tedesco standing on the edge of one of four moulins (drainage holes) he and his team found at the bottom of a supraglacial lake during the expedition to Greenland in the summer, 2011. PHOTO COURTEST P. ALEXANDER.

Feedback loop reinforces rapid ice loss

By Summit Voice

SUMMIT COUNTY —Temperatures don’t have to reach record highs to fuel extreme melting of the Greeland ice cap, according to new research suggesting that glaciers could undergo a self-amplifying cycle of melting and warming that would be difficult to halt.

“We are finding that even if you don’t have record-breaking highs, as long as warm temperatures persist you can get record-breaking melting because of positive feedback mechanisms,” said Dr. Marco Tedesco, assistant professor in the Department of Earth and Atmospheric Sciences at The City College of New York.

Tedesco, who directs CCNY’s Cryospheric Processes Laboratory, collected data for the analysis this past summer during a four-week expedition to the Jakobshavn Isbræ glacier in western Greenland.  Their arrival preceded the onset of the melt season.

Combining data gathered on the ground with microwave satellite recordings and the output from a model of the ice sheet, he and graduate student Patrick Alexander found a near-record loss of snow and ice this year. The extensive melting continued even without last year’s record highs. Continue reading “Global warming: Researchers find extreme melting of Greenland ice cap even without record temperatures”

Forecasters pinpoint La Niña winter impacts

National Weather Service offers a detailed explanation of how La Niña might affect Colorado’s fall and winter weather in 2010-2011

Northwest Colorado could see heavy snows this winter if La Niña kicks in as predicted.

By Summit Voice

SUMMIT COUNTY — National Weather Service forecasters are pinpointing the potential effects of strengthening La Niña conditions this winter, predicting a dry winter on Colorado’s eastern plains and in the southern part of the state, but above-average snowfall for the northwestern quadrant of Colorado.

The forecasters said there is still some disagreement about whether this year’s La Niña will be a strong event, but they said that the strong cooling of sea surface temperatures in the eastern Pacific and a positive feedback loop of the ocean and atmosphere are tilting the odds in favor of a moderate to strong La Niña.

La Niña is a cooling of sea surface temperatures in the eastern and central Pacific that affects the track of the storm-bearing jet stream.

The long-range forecast is not just important for Summit powder hounds, but for the state’s water managers trying to plan reservoir operations for the coming year. See the entire powerpoint here. Continue reading “Forecasters pinpoint La Niña winter impacts”