Monday, December 20, 2010

So now they are not sure if we have caused warming or cooling!

So if they are not sure what we humans have caused, then how can they know the solution? 

Thanks Mac, Aivars Lode

Posted at 10:00 AM ET, 12/20/2010

Freak pattern brings Europe record cold & snow

By Andrew Freedman

Same pattern supporting cold in eastern U.S.

One of the fiercest beginnings to winter on record has slammed Europe with relentless assaults of bitter cold and heavy snowfalls. The unusually wintry weather gripping Europe as well as the cold plaguing the eastern United States are linked by a historically strong weather system locked over Greenland.
Pedestrians walk during a snow-fall in central London, Saturday, Dec. 18, 2010. Plunging temperatures and heavy snow saw large swathes of Britain grind to a standstill, as London's Gatwick Airport closed its runway and British Airways cancelled flights at Heathrow. (AP Photo/Alastair Grant) (Alastair Grant - AP).
In Europe, the strange weather pattern has caused mayhem for holiday travel. Over the weekend, airport and ground transportation disruptions were widespread, from London's Heathrow Airport - one of the world's busiest hubs - to Frankfurt International Airport and the German Autobahn. According to the The Guardian newspaper, Frankfurt airport workers resorted to dressing up as angels in an attempt to calm the situation when crowds of stranded passengers, frustrated by lengthy delays and flight cancellations, became unruly. Heathrow, meanwhile, was closed to arriving aircraft on Sunday, after being closed altogether on Saturday, according to several news reports. More heavy snow is forecast for London yet again today according to the UK Met Office.
BAA spokesman Andrew Teacher told CNN: "These are absolutely ... freak weather conditions ... We've not seen a storm like this in 20 years."
So what has been causing this freak winter weather onslaught in Europe, and the colder-than-average conditions in much of the eastern U.S., including Washington?
There is a very strong "blocking pattern" in place over Greenland, which is helping to steer a parade of storms into the British Isles and mainland Europe, while pumping abnormally mild air into portions of the Canadian Arctic. In short - the atmosphere is jammed up like the Beltway at rush hour. Storm systems have nowhere to go, and are doing weird loop-de-loops up into the Canadian Maritimes, and even off the coast of the Pacific Northwest.
Temperatures relative to average in Wabush Lake, Canada (Newfoundland), on the warm side of the blocking high pressure system, have been much warmer than average as mild air invades the eastern Arctic. Source: NOAA.
Meteorologists with Environment Canada described the atmospheric circulation as "one of the most bizarre patterns in recent memory".
The high pressure cell parked over Greenland is not your ordinary High. It's unusually strong, and has boosted pressures, often referred to by meteorologists as "geopotential heights", in parts of the Arctic to record levels. For example, pressure typically found at about 18,000 feet above sea level have increased so significantly in recent days that it may have set several records, including the record for the largest departure from average for anywhere on the planet in any month of the year since such historical records began in 1948 (this analysis was performed by the Weather Channel's Stu Ostro).
heights anomaly map 12_1 to 12_18.gif
Pressure or "height" departures from average over the Northern Hemisphere. Positive height departures (yellows, oranges and reds) from average are associated with warmer than normal temperatures and negative height (blues) departures are associated with colder than average temperatures. Source: NOAA.
These pressure or "height" changes can be clearly seen in the image to the right with the red shades near the southern tip of Greenland indicating the extraordinarily high pressure, as well as this animation, both from the Climate Prediction Center.
The circulation around that High is helping to pump mild air into eastern Canada, while locking unusually cold air in place in the eastern U.S., in addition to driving record cold and snow into the heart of Western Europe. According to the Associated Press, the snow and bitter cold may set a new monthly record for Britain:

"Britain's national weather forecaster, the Met Office, said the nation has experienced the heaviest snow falls in December in decades and is on course for record low temperatures. "You have to look back to December 1981 to find similar snow depths," forecaster Helen Chivers said. "If the second half of the month is as cold as the first, this will be the coldest December on record since 1910."
According to The Telegraph, Britain's current average temperature for the month of December is running five degrees Celsius below the long-term average for the month.
The cold and snow has not only disrupted holiday travelers. A Lady Gaga concert had to be rescheduled when trucks carrying the pop singer's sets could not make it to Paris' Bercy Stadium, the AP reported.
Might there be larger forces at work?
The current weather pattern is in part related to the North Atlantic Oscillation or NAO, which is a natural climate cycle that influences winter weather in parts of the Northern Hemisphere. When the NAO is in a negative phase like it is now, the likelihood of major snowstorms in the mid-Atlantic increases, as does the likelihood of winter storms in parts of Europe. The NAO was in an extreme negative phase during most of last winter, and has been negative recently as well.

The daily NAO index from September through December 19, 2010. Credit: Climate Prediction Center.
The current weather pattern may also be indirectly related to long-term climate change. Meteorologist Stu Ostro of The Weather Channel has documented a trend of increased occurrences of atmospheric pressure anomalies, such as the one observed above Greenland, and he believes these may be tied to atmospheric warming from greenhouse gas emissions.
Also, recent research indicates that Arctic sea ice decline may influence winter weather patterns.
According to the National Snow and Ice Data Center (NSIDC), November sea ice extent was the second lowest on record since 1979. "Typically by the end of November, nearly half of Hudson Bay has iced over. But on November 30, only 17% of the bay was covered by sea ice. Compared to the 1979 to 2000 average, the ice extent was 12.4% below average for the Arctic as a whole," an NSIDC report stated.
This year's "Arctic Report Card", issued by the National Oceanic and Atmospheric Administration (NOAA), found that warming water and air temperatures associated with the decline of summer sea ice has been raising the height of atmospheric pressure surfaces over the North Pole.

Warming of the Arctic may favor a pattern pushing colder air over the eastern U.S. and Europe. Source: Climate Central
The report noted that the winter of 2009-2010 featured "one of the three largest Arctic high-pressure events since 1850." These higher pressure surfaces are thought to change large-scale wind patterns and can lead to bouts of severe winter weather in the eastern United States.
"Models suggest that loss of sea ice in fall favors higher geopotential heights over the Arctic. With future loss of sea ice, such conditions as winter 2009-2010 could happen more often. Thus we have a potential climate change paradox. Rather than a general warming everywhere, the loss of sea ice and a warmer Arctic can increase the impact of the Arctic on lower latitudes, bringing colder weather to southern locations," the report stated.
By Andrew Freedman  | December 20, 2010; 10:00 AM ET

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