Not just March, but start of 2012 shatter US records for heat, worrying meteorologists
By Associated Press, Updated: Monday, April 9, 2012 10:46 AM
WASHINGTON — It has been so warm in the United States this year, especially in March, that national records were not just broken, they were deep-fried.
Temperatures in the lower 48 states were 8.6 degrees (4.8 degrees Celsius) above normal for March and 6 degrees (3.3 degrees Celsius) higher than average for the first three months of the year, according to calculations by the National Oceanic and Atmospheric Administration. That far exceeds the old records.
The magnitude of how unusual the year has been in the U.S. has alarmed some meteorologists who have warned about global warming. One climate scientist said it is the weather equivalent of a baseball player on steroids, with old records obliterated.
“Everybody has this uneasy feeling. This is weird. This is not good,” said Jerry Meehl, a climate scientist who specializes in extreme weather at the National Center for Atmospheric Research in Boulder, Colo. “It’s a guilty pleasure. You’re out enjoying this nice March weather, but you know it’s not a good thing.”
It’s not just March.
“It’s been ongoing for several months,” said Jake Crouch, a climate scientist at NOAA’s National Climatic Data Center in Asheville, N.C.
Meteorologists say an unusual confluence of several weather patterns, including La Nina, was the direct cause of the warm start to 2012. While individual events cannot be blamed on global warming, Crouch said this is like the extremes that are supposed to get more frequent because of man-made climate change. Greenhouse gases come from the burning of fossil fuels such as coal and oil.
It is important to note that this unusual winter heat is mostly a North America phenomenon. Much of the rest of the Northern Hemisphere has been cold, said NOAA meteorologist Martin Hoerling.
The first quarter of 2012 broke the January-March record by 1.4 degrees (0.8 degrees Celsius). Usually records are broken by just one- or two-tenths of a degree. U.S. temperature records date from 1895.
The atypical heat goes back even further. The U.S. winter of 2010-2011 was slightly cooler than normal and one of the snowiest in recent years, but after that things started heating up. The summer of 2011 was the second warmest summer on record.
The winter that just ended, which in some places was called the year without winter, was the fourth warmest on record. Since last April, it has been the hottest 12-month stretch on record, Crouch said.
But the month where the warmth turned especially weird in the United States was March.
Normally, March averages 42.5 degrees (5.8 degrees Celsius) across the country. This year, the average was 51.1 (10.6 degrees Celsius), which is closer to the average for April. Only one other time, in January 2006, was the country as a whole that much hotter than normal for an entire month.
The “icebox of America,” International Falls, Minn., saw temperatures in the 70s for five days in March, and there were only three days of below zero temperatures all month.
In March, at least 7,775 weather stations across the nation broke daily high temperature records, and another 7,517 broke records for night-time heat. Combined, that is more high temperature records broken in one month than ever before, Crouch said.
“When you look at what’s happened in March this year, it’s beyond unbelievable,” said University of Victoria climate scientist Andrew Weaver.
NOAA climate scientist Gabriel Vecchi compared the increase in weather extremes to baseball players on steroids: You can’t say an individual homer is because of steroids, but they are hit more often and the long-held records for home runs fall.
They seem to be falling far more often because of global warming, said NASA top climate scientist James Hansen. In a paper he submitted to the journal Proceedings of the National Academy of Sciences and posted on a physics research archive, Hansen shows that heat extremes aren’t just increasing but happening far more often than scientists thought.
What used to be a 1-in-400 hot temperature record is now a 1 in 10 occurrence, essentially 40 times more likely, said Hansen. The warmth in March is an ideal illustration of this, said Hansen, who also has become an activist in fighting fossil fuels.
Weaver, who reviewed the Hansen paper and called it “one of the most stunning examples of evidence of global warming.”
The Ronne-Filchner Ice Shelf in West Antarctica rapidly breaking up. Top image taken on the afternoon of 12 January 2010. Bottom image taken 24 hours later on the afternoon of 13 January 2010. NASA images courtesy Jeff Schmaltz, MODIS Rapid Response Team at NASA GSFC [ http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=42302 ]
Which means even though summer air temperatures have not yet warmed enough to substantially melt Antarctica's surface snows, the oceans are undermining the frozen continent from below—fueling a recent, widespread, and intensifying glacier acceleration and its accompanying rise in sea levels.
The results are based on 4.5 million measurements made by a laser instrument mounted on NASA's now defunct ICESat satellite [ http://icesat.gsfc.nasa.gov/ ] between 2003 and 2008, which mapped the thickness of most floating ice shelves around Antarctica. The results:
¦ Of 54 ice shelves mapped, 20 are being melted by warm ocean currents, most of those in West Antarctica.
¦ In all cases the inland glaciers that flow down to the coast and feed into these thinning ice shelves have accelerated, draining more ice into the sea and contributing to sea-level rise.
The melting is happening fastest where deep troughs cut through the underwater continental shelf, allowing warmer water access to the undersides of the ice shelves.
"What’s really interesting is just how sensitive these glaciers seem to be. Some ice shelves are thinning by a few meters a year and in response the glaciers drain billions of tons of ice into the sea. This supports the idea that ice shelves are important in slowing down the glaciers that feed them, controlling the loss of ice from the Antarctic ice sheet... We think [the cause is] linked to changes in wind patterns. Studies have shown that Antarctic winds have changed because of changes in climate and that this has affected the strength and direction of ocean currents. As a result warm water is funnelled beneath the floating ice. These studies and our new results therefore suggest that Antarctica’s glaciers are responding rapidly to a changing climate.
You can see that happening in this NASA video [ http://www.youtube.com/watch?v=08sDlxhNEHQ (above)] which shows warm ocean currents attacking the underside of ice shelves. Ice shelves colored red are thicker (greater than 1,800 feet / 550 meters). Those colored blue are thinner (less than 650 feet / 200 meters).
Antarctic ice melting from warm water below: study
April 26, 2012 - 10:18AM
Antarctica's massive ice shelves are shrinking because they are being eaten away from below by warm water, a new study finds.
That suggests that future sea levels could rise faster than many scientists have been predicting.
The western chunk of Antarctica is losing 23 feet (seven metres) of its floating ice sheet each year. Until now, scientists weren't exactly sure how it was happening and whether or how man-made global warming might be a factor. The answer, according to a study published Wednesday in the journal Nature, is that climate change plays an indirect role — but one that has larger repercussions than if Antarctic ice were merely melting from warmer air.
Hamish Pritchard, a glaciologist at the British Antarctic Survey, said research using an ice-gazing NASA satellite showed that warmer air alone couldn't explain what was happening to Antarctica. A more detailed examination found a chain of events that explained the shrinking ice shelves.
Twenty ice shelves showed signs that they were melting from warm water below. Changes in wind currents pushed that relatively warmer water closer to and beneath the floating ice shelves. The wind change is likely caused by a combination of factors, including natural weather variation, the ozone hole and man-made greenhouse gases, Pritchard said in a phone interview.
As the floating ice shelves melt and thin, that in turn triggers snow and ice on land glaciers to slide down to the floating shelves and eventually into the sea, causing sea level rise, Pritchard said. Thicker floating ice shelves usually keep much of the land snow and ice from shedding to sea, but that's not happening now.
That whole process causes larger and faster sea level rise than simply warmer air melting snow on land-locked glaciers, Pritchard said.
"It means the ice sheets are highly sensitive to relatively subtle changes in climate through the effects of the wind," he said.
What's happening in Antarctica "may have already triggered a period of unstable glacier retreat", the study concludes. If the entire Western Antarctic Ice Sheet were to melt — something that would take many decades if not centuries — scientists have estimated it would lift global sea levels by about 16 feet (4.87 metres).
NASA chief scientist Waleed Abdalati, an expert in Earth's ice systems who wasn't involved in the research, said Pritchard's study "makes an important advance" and provides key information about how Antarctica will contribute to global sea level rise.
Another outside expert, Ted Scambos of the National Snow and Ice Data Centre, said the paper will change the way scientists think about melt in Antarctica. Seeing more warm water encircling the continent, he worries that with "a further push from the wind" newer areas could start shrinking.
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