January 12, 2010
Experts Divided On Implications Of Brutal Cold Spell
This year's fierce winter in much of the Northern Hemisphere is only the beginning of a global trend towards cooler weather that is likely to last decades, say some of the world's most renowned climate scientists. However, other experts say the cold spell does not contradict an overall trend of global warming.
A report on Sunday by the British newspaper The Mail cited forecasts by eminent climate scientists that are a direct challenge to some of the most deeply held beliefs among those who say the world is experiencing global warming "“ including claims that the North Pole will be ice-free by the summer of 2013.
Indeed, according to the U.S. National Snow and Ice Data Center in Colorado, summer Arctic sea ice has increased by 409,000 square miles, roughly 26 percent, since 2007 "“ a figure that even the most ardent global warming believers do not dispute.
The scientists' predictions also challenge standard climate computer models, which contend that the Earth's warming since the year 1900 is due solely to man-made greenhouse gas emissions, and will continue until CO2 levels taper off.
But the climate scientists say their research shows instead that much of the warming during the last century was caused by "Ëwarm mode' oceanic cycles, as opposed to the present "Ëcold mode'.
This challenge to the theory of man-made global warming carries weight, given they come from prominent climate scientists that cannot be defined simply as global warming deniers.
Both of Britain's major political parties maintain that the world is facing imminent disaster without dramatic CO2 reductions. And many say the science of global warming is "Ësettled'.
Professor Mojib Latif, who leads a research team at the Leibniz Institute at Germany's Kiel University, is a leading member of the UN's Intergovernmental Panel on Climate Change (IPCC). Since its inception 22 years ago, the IPCC has been working to get the issue of man-made global warming on to the international political agenda.
Professor Latif has developed new techniques for measuring ocean temperatures far beneath the surface, where cooling and warming cycles begin. In a paper published last year, he and his colleagues predicted the new cooling trend, and even warned of it again at a conference last September.
"A significant share of the warming we saw from 1980 to 2000 and at earlier periods in the 20th Century was due to these cycles "“ perhaps as much as 50 percent," he said during an interview with The Mail on Sunday.
"They have now gone into reverse, so winters like this one will become much more likely. Summers will also probably be cooler, and all this may well last two decades or longer," he said.
"The extreme retreats that we have seen in glaciers and sea ice will come to a halt. For the time being, global warming has paused, and there may well be some cooling."
But amid bitter cold temperatures that froze much of Europe, Asia and North America last week, many insisted this was merely a "Ëblip' of no significance.
Britain's BBC assured its viewers that the dramatic cold spell was merely short-term "Ëweather' unrelated to the "Ëclimate', which was still warming.
But Professor Latif's work and that of other scientists refutes that view.
Although the current freezing temperatures are indeed a result of the "ËArctic oscillation' "“ an anomaly that consists of a vast high-pressure system over Greenland that drives polar winds far to the south "“ meteorologists say it is the strongest for at least six decades. This has caused the jetstream that typically runs over the English Channel to run instead over the Strait of Gibraltar.
Professor Latif says this, in turn, results in much longer-term shifts known as the Pacific and Atlantic "Ëmulti-decadal oscillations' (MDOs).
These effects are not confined to the Northern Hemisphere, according to Professor Anastasios Tsonis, who leads the University of Wisconsin Atmospheric Sciences Group.
Professor Tsonis has recently shown that these MDOs move together in a synchronized fashion throughout the world, causing abrupt changes in the world's climate from a "Ëwarm mode' to a "Ëcold mode' and back again in 20 to 30-year cycles.
"They amount to massive rearrangements in the dominant patterns of the weather," he told The Mail yesterday.
"And their shifts explain all the major changes in world temperatures during the 20th and 21st Centuries."
"We have such a change now and can therefore expect 20 or 30 years of cooler temperatures."
A strong warm mode occurred during the period from 1915 to 1940, reflected in rising temperatures, Professor Tsonis added. However, the world cooled from 1940 until the late Seventies, the last MDO cold-mode era, despite rising levels of atmospheric CO2.
Many of the consequences of the recent warm mode were also observed 90 years ago, The Mail reported, citing a 1922 Washington Post report that described Greenland's disappearing glaciers and Arctic seals that found "Ëthe water too hot'. Indeed, warm Gulf Stream water was still detectable just a few hundred miles of the North Pole at the time.
In contrast, last week 56 percent of the surface of the United States was covered by snow, Professor Tsonis said.
"That hasn't happened for several decades."
"It just isn't true to say this is a blip. We can expect colder winters for quite a while," he said, adding that towards the end of the last cold mode the world's media were consumed by fears of freezing.
The Mail cited a 1974 a Time magazine cover entitled "Another Ice Age".
"Man may be somewhat responsible "“ as a result of farming and fuel burning [which is] blocking more and more sunlight from reaching and heating the Earth," the story read.
"Perhaps we will see talk of an ice age again by the early 2030s, just as the MDOs shift once more and temperatures begin to rise," Tsonis told The Mail.
However, he is not a climate change "Ëdenier', and attributes a small amount of "Ëbackground' warming to human activity and greenhouse gases. But he questions the dire predictions others have put forth.
"I do not believe in catastrophe theories. Man-made warming is balanced by the natural cycles, and I do not trust the computer models which state that if CO2 reaches a particular level then temperatures and sea levels will rise by a given amount."
"These models cannot be trusted to predict the weather for a week, yet they are running them to give readings for 100 years."
Professor Tsonis said he was flooded with "Ëhate emails' after publishing his work in the journal Geophysical Research Letters.
"People were accusing me of wanting to destroy the climate, yet all I'm interested in is the truth," he said.
He also received complaints from climate change skeptics, may of whom said he had not gone far enough in debunking the theory of man-made global warming.
The work of Professors Latif and Tsonis raised a critical issue: How much of the late 20th Century warming was caused not by carbon dioxide, but by MDOs?
While Tsonis did not give a figure, Latif suggested it could be somewhere between 10 and 50 percent.
Meanwhile, other critics of man-made global warming attribute an even greater role played by MDOs.
William Gray, emeritus Professor of Atmospheric Sciences at Colorado State University, said that while he believed greenhouse gases were responsible for some background rise in temperatures, the computer models used by global warming advocates had vastly exaggerated their effect.
These models, he said, distort the way the atmosphere works.
"Most of the rise in temperature from the Seventies to the Nineties was natural," Professor Gray told The Mail.
"Very little was down to CO2 "“ in my view, as little as five to ten percent," he said.
Nevertheless, many passionate advocates of man-made global warming dismiss the ideas that MDOs were having any impact on the world's climate.
In March 2000, Dr. David Viner, at the time a member of the University of East Anglia Climatic Research Unit, said that snowfall in Britain would become a very rare event within just a few years.
The University of East Anglia Climatic Research Unit is currently under investigation in the so-called "Ëclimategate' leaked emails.
Dr. Viner, who now heads a British Council program that raises awareness of global warming among young people abroad, said last week he still stands by his prediction.
"We've had three weeks of relatively cold weather, and that doesn't change anything. This winter is just a little cooler than average, and I still think that snow will become an increasingly rare event."
Other scientists agree with Dr. Viner, saying the frigid weather that has engulfed enormous swathes of the northern hemisphere is unusual, but does not contradict an overall global trend of warming.
They, too, say the recent brutal snowstorms and freezing temperatures in North America, Northern Europe and parts of Asia are attributable to Arctic Oscillation, also known as Northern Hemisphere Annular Mode or the North Atlantic Oscillation.
"It's a relatively abnormal pattern but it's not unprecedented at all, it's something that happens every 10 years or so," said Barry Gromett of Britain's Met Office in an interview with the AFP news agency.
"It's like a great big boulder in the stream. It cuts off Europe's supply of mild, moist Atlantic air. Instead, we get Arctic winds that feed in clockwise, which means we get the cold stuff off Scandinavia and the Arctic regions," Gromett said.
These bitter cold air streams are also deflected around the "boulder" into North America, he said, and strengthen the grip of the Siberian high-pressure system, which intensifies cold weather in parts of Asia.
Gromett noted that while some parts of the world are experiencing extreme low temperatures, others are having unusual highs as a result of warmer winds directed to different areas.
Indeed, parts of Canada and Alaska have seen temperatures nine to 18 degrees Fahrenheit above normal, while parts of North Africa and the Mediterranean basin have also seen unusually warm temperatures.
"In fact, in the first week of January, Crete recorded a temperature of more than 30 C (86 F)," Gromett said.
Michel Daloz with the French national weathercaster Meteo France said this year's northern hemisphere's cold spell was relatively mild by historical comparison.
"The natural variability of the climate means that there are troughs of cold from time to time," he told the AFP.
"There were temperatures of between -25 and -15 C (-13 F to 5 F) across France" in 1956, 1963 and 1985, he said.
Nor did it challenge data indicating persistent warming, he said.
"In fact, in early December, our main focus was on the clement weather."
Indeed, the Met Office said that 2009 was provisionally the fifth warmest on record, with 2010 potentially being the warmest ever, due to man-made greenhouse gas emissions and a return to El Nino -- a natural warming phenomenon triggered by warmer waters in the western Pacific Ocean.
El Nino reappeared in June 2009, and according to the UN's World Meteorological Organization (WMO) will likely persist through early 2010.
WMO expert Omar Baddour said the present Arctic Oscillation was likely most severe in 30 to 50 years.
"Generally it lasts a few weeks or a month, a month and a half. It started in December, so we are nearing the end of the episode," Baddour said in Geneva.
On the Net:
- National Snow and Ice Data Center
- Leibniz Institute - Kiel University
- Intergovernmental Panel on Climate Change
- University of Wisconsin Atmospheric Sciences Group
- Geophysical Research Letters
- Colorado State University, Atmospheric Sciences
- University of East Anglia Climatic Research Unit
- Met Office
- Meteo France
- World Meteorological Organization
- Image Courtesy Wikipedia