The Warming Earth Blows Hot, Cold and Chaotic

Subtle Rises in Temperature Make for Wild Weather; 'Exceptionally Unusual' Becomes the New Normal
By ROBERT LEE HOTZ

SAN FRANCISCO -- Three independent research groups have concluded that 2008 was a comparatively cool year on planet Earth -- a feverish chill on our warming world.
The year's average global temperature was the 9th or 10th warmest since reliable record-keeping began in 1850, and the coldest since the turn of the 21st century, according to separate surveys by the United Nations' World Meteorological Organization, NASA's Goddard Institute of Space Studies, and the U.S. National Climatic Data Center. Each used slightly different methods to rank 2008 based on world-wide land and sea-surface temperatures through November.
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The U.S. Climate Change Science Program analyzed North America's climate records for the last 56 years in "Reanalysis of Historical Climate Data for Key Atmospheric Features: Implications for Attribution of Causes of Observed Change" and found the yearly average temperature for the continent increased by 1.6 degrees Fahrenheit.
The program's researchers also assessed the chances of catastrophic climate changes during the next century in "Abrupt Climate Change," released last month.
The past year through was the coolest year since 2000, says the 2008 Meteorological Year Summation by NASA's Goddard Institute of Space Studies. The U.S. National Climatic Data Center said the year 2008 is on track to be one of the ten warmest years on record for the globe.
The World Meteorological Organization said 2008 is likely to rank as the 10th warmest year on record since the beginning of its instrumental climate records in 1850.
For the time being, no one knows whether this temperature drop heralds a lasting retreat from global warming or a temporary dip. Last summer was relatively cool world-wide, for example, while global land temperatures in October were the warmest for that month in more than a century, government weather records show. Taken together, the result was a year that ran slightly less than one degree warmer than the 20th century mean.
In matters of climate, the unusual is becoming routine, as higher temperatures make weather patterns more unstable. "As a result of climate change," says Peter Stott, head of climate monitoring at the U.K.'s Hadley Center, which helped prepare the U.N. figures, "what would have once been an exceptionally unusual year has now become quite normal."
Despite the ups and downs of annual temperature swings, though, the planet has grown steadily warmer in recent decades, affecting everything from New England winters and the Siberian spring to western droughts and tropical cloud cover. That's according to eight new government and university climate studies presented last month during a meeting in San Francisco of the American Geophysical Union, an international scientific society of 50,000 researchers who study Earth and its environment.
Moreover, almost all of the warming in North America has taken place since 1970, says a team of government and academic experts at the U.S. Climate Change Science Program.
Looking beyond the variations of any single year, these studies chronicle growing evidence of climate changes and suggest the effects of rising temperatures are accelerating.
"I do believe we are entering a new state," says arctic researcher Julienne Stroeve at the National Snow and Ice Data Center in Boulder, Colo. "Ice loss is happening faster than the climate models are showing."
Since 2003, for instance, more than two trillion tons of land ice in Greenland, Antarctica and Alaska have melted, adding enough water to oceans to raise global sea level by one-fifth of an inch, NASA geophysicists reported at the conference.
Alaska's low-lying ice fields are disappearing at two to three times the rate of a decade ago, according to aerial surveys by researchers at the University of Alaska. Since 2000, Greenland alone has lost 355.4 square miles of ice -- an area 10 times the size of Manhattan -- Ohio State University researchers reported. Using data from two NASA satellites, they determined that Greenland's 32 largest glaciers lost three times as much ice last year as the year before.
"I wouldn't run for the hills," says glacier analyst Eric Rignot at NASA's Jet Propulsion Laboratory. "But it might be time to start walking."
In another sign of polar thaw, researchers have detected new seeps of methane bubbling up from formerly frozen seafloor lodes along the Siberian coast. Methane, like carbon dioxide, is a potent greenhouse gas that helps trap heat in the atmosphere and could accelerate any warming trend. "We have enough data to worry," says Igor Semiletov at the University of Alaska Fairbanks who reported the methane leaks.
Warming temperatures also are influencing more temperate latitudes, several recent studies show.
By analyzing five years worth of infrared measurements from NASA's Aqua satellite, JPL researchers found that high-altitude tropical storm and rain clouds are increasing. At the present rate of warming, the scientists reported last month, tropical storms can be expected to increase by 6% every 10 years.
Last year, the Atlantic hurricane season was the fourth most active in 64 years and the first to have a major hurricane in each month from July through November, according to federal meteorologists at the National Oceanic and Atmospheric Administration. There also were 1,700 tornadoes catalogued in the U.S. from January through November, ranking last year just behind 2004 for the most twisters recorded in a year. The tornado records date back to 1953.
The 2008 storm season across most tropical cyclone regions, however, was slightly below average, NOAA records show.
All in all, solar heat is the energy that drives the world's weather, and rising levels of greenhouse gases such as carbon dioxide and methane are allowing more of that energy to build up in the atmosphere every year, experts say.
Overall, the world's atmosphere warmed by 0.72 degrees Fahrenheit during the past 30 years, according to a comprehensive analysis of monthly satellite temperature readings by John Christy, head of the Earth System Science Center at the University of Alabama in Huntsville, which was released last month.
But on the hot plate of planet Earth, that warming isn't evenly distributed. Changing sea ice, ocean currents and winds mute or accelerate regional temperatures changes by redistributing the heat in the atmosphere.
A quarter of the globe warmed at least one full degree Fahrenheit since the satellite readings started in 1978. The warming was most pronounced in northern latitudes. A few isolated areas in Antarctica actually cooled by at least half of one degree Fahrenheit.
Across North America, such regional variation is the norm, say experts at the U.S. Climate Change Science Program. They analyzed the continent's climate records for the last 56 years and, in a report released last month, showed that some regional temperatures rose sharply, and others showed no change at all. The yearly average temperature for the entire continent increased by 1.6 degrees Fahrenheit.
Across the northern reaches of Alaska, the Yukon territories and Alberta and Saskatchewan, average annual temperatures increased up to 3.6 degrees Fahrenheit, they reported. But there were no significant yearly average temperature changes in the southern U.S. or eastern Canada.
In New England, rising temperatures have taken some of the chill out of winter.
After analyzing 40 years of wintertime data, researchers at the University of New Hampshire found that seasonal temperatures in the northeastern U.S. had risen about 0.42 degrees Celsius per decade, from 1965 through 2005.
The warming was most pronounced in the region's coldest months of January and February, they reported in the Journal of Geophysical Research-Atmospheres. The number of snow days each winter dropped at a rate of 8.9 days per decade and annual snowfall decreased by about 1.8 inches per decade, the researchers reported.
So many subtle changes in so many different places, building up decade after decade, add up to something more than the weather's natural variation.
To a seasoned eye, day-to-day weather patterns now seem chaotic. Among the Inuit of the eastern Canadian Arctic, University of Colorado researchers reported last month, many elders are no longer willing to trust their forecasting skills, honed by a life in the field, to guide local hunting parties and travelers.

Robert Lee Hotz shares recommended reading on this topic and responds to reader comments at WSJ.com/OnlineToday. Email him at sciencejournal@wsj.com.