As the Earth Heats Up, Many Questions Remain
Two miles up, above black lava fields and a white blanket of clouds, a tower rising from this U.S. government observatory gulps in some of the clear, crisp air and gets a taste of man’s future on Earth.
“As big as the atmosphere is, we’re influencing it,” said the physicist in charge, John Barnes.
The tale told by the tower, atop a dormant Hawaiian volcano, can be read in the upward curve of a graph:
Carbon dioxide in the atmosphere, which stood at 280 parts per million two centuries ago, has climbed to 379 ppm since industrializing man began burning vast amounts of coal, oil and other fossil fuels.
There has not been, for 450,000 years, this much CO2 enveloping the planet, ice-core samples show.
The news from Mauna Loa and other monitoring stations has increasingly disturbed scientists because carbon dioxide traps heat, as do other “greenhouse gases” generated by humans, and global temperatures have, indeed, been rising -- by almost 1 degree Fahrenheit over a recent 18-year period, a relatively rapid increase, NASA experts reported in April.
Warming will disrupt our climate, possibly drying out farmlands, stirring up fiercer storms and raising ocean levels, among other impacts, says the Intergovernmental Panel on Climate Change, a U.N.-organized network of hundreds of climatologists and other researchers.
But the climate tale is far from simple. Earth’s behavior -- physics, chemistry, biology -- is an infinitely complex web of feedback loops, reactions, recycling among the atmosphere, ocean, land and all their components. Knowns are countered by unknowns, certainty by uncertainty.
It was uncertainties that American oil, utility and other industries pointed to in the 1990s in fighting international efforts to cap fossil-fuel emissions. And President Bush cited the “incomplete state of scientific knowledge” when he renounced the Kyoto Protocol, the first step toward imposing those caps, in March 2001.
Then, just three months later, a National Academy of Sciences report commissioned by the Bush White House supported the U.N. panel’s finding, declaring in its opening sentence: “Greenhouse gases are accumulating in the Earth’s atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise.”
Last year, two more prestigious organizations -- the American Meteorological Society and the American Geophysical Union -- came to similar conclusions.
In the past, skeptics on climate change often focused on discrepancies between satellite and ground temperature readings, suggesting that recent warming might be minimal. But deeper analysis has largely dispelled those doubts. By the time scientists gathered for a symposium at New York’s Columbia University in April, just weeks after Mauna Loa Observatory recorded CO2 topping 379, skeptics seemed to have faded -- or at least switched to a better-safe-than-sorry view.
“I’m a skeptic,” Harvard University’s Michael B. McElroy told fellow scientists. “But I take out fire insurance on my home.”
The temperature rise is believed to be the most rapid in at least 10,000 years.
“It’s been getting warmer and we can’t explain that by natural causes,” Richard Alley of Pennsylvania State University said at Columbia.
“I couldn’t absolutely, positively, 100% say there’s no other cause, but it’s consistent with carbon dioxide warming.”
Climatologists will never dispel the uncertainties 100%, but they’re working on it, and the Geophysical Union said computer modeling of carbon, water and other cycles governing climate had improved greatly in the last decade.
At universities and major centers worldwide -- such as the U.S. government’s National Center for Atmospheric Research in Boulder, Colo., and Britain’s Hadley Centre -- specialists peer into the future via supercomputers, setting in motion vast global calculations via thousands of interlocked mathematical formulas.
Weather fronts flicker past on screens in blue and white, as temperatures and rainfall, melting ice and ocean evaporation, cloud cover and myriad other factors play out over days, months, years in “general circulation models,” or GCMs.
The leapfrogging of computer speed has boosted scientists’ confidence.
“The models used to consist of, say, 50,000 lines of computer code,” said an early modeler, V. Ramanathan of the Scripps Institution of Oceanography in San Diego. “Now they have 500,000 lines of code.”
But if computer power is meeting the challenge, brainpower -- numbers of trained specialists, hands on keyboards to input, minds to analyze -- is coming up short, scientists said in a series of interviews.
“Models have become more sophisticated, but still they’re missing so many things,” Ramanathan said.
“Climate change probably deserves a Manhattan Project-scale effort,” said Scripps meteorologist Richard C.J. Somerville, referring to the World War II atom-bomb project. “What there is is a few dozen GCM projects, each with a handful of people.”
Whatever the resources, no one expects a “eureka moment” from the modeling -- ironclad proof that last month’s automobile exhausts caused this month’s warming. In fact, the added sophistication raises new questions even as it helps answer old ones.
“All these little things now pop up. What about the size of raindrops, what about sea ice, what about forests?” said senior scientist Wallace Broecker of Columbia, who in the 1970s raised early alarms about global warming.
“We’re going to have to make a decision on what to do on the basis of insufficient evidence.”
The uncertainty compounds the concern. For example, some believe that global warming will shrink “natural carbon sinks” -- that is, drought will kill off rainforests, which absorb carbon dioxide. That would raise levels of the gas in the atmosphere, worsening warming in a dangerous circular feedback.
“If we get going now [on emission controls], we essentially buy time for further research” on such questions, said Jorge L. Sarmiento, Princeton University climatologist.
The greatest uncertainties have long focused on clouds -- in their variety and small-scale dynamics. Clouds both reflect sunlight, helping cool the planet, and act like a blanket, keeping Earth warm.
“When you have competing effects like that, it’s difficult to model,” said David Pierce, a veteran Scripps modeler.
But progress is being made, especially by U.S. Energy Department scientists studying clouds in minute detail over tens of thousands of square miles of Oklahoma, Alaska and the western Pacific.
Newer concerns focus on the unknowns of aerosols, or particulates -- tiny atmospheric particles of many kinds, from smokestack soot to dust blown off the desert. Some particulates cool by scattering sunlight; some warm. Some help clouds form; some break up clouds.
Atop Mauna Loa, amid the silvery domes of the National Oceanic and Atmospheric Administration observatory, Barnes is researching aerosols in the stratosphere, firing a laser’s green beam into the night sky to measure particles as far as 50 miles up.
Leading NASA scientist James Hansen believes that climate models may have missed a major particulate effect, from industrial soot accumulating on northern snow and ice. Instead of reflecting almost all sunlight, the darker landscape must be absorbing more heat, his team theorizes.
An aura of quiet urgency is building around climate research.
The tools deployed can dazzle, from distant space to ocean depths.
A NASA satellite, from 1 million miles away, will view the entire sunlit Earth and measure its heat exchanges. To study ocean-climate interaction, meanwhile, 20 nations are sending 3,000 technology-packed floats as much as a mile deep in seas worldwide to drift with currents for years, taking temperature and other readings, and surfacing regularly to radio home the results via satellite.
Many believe that the most urgently needed data will come from ICESat, a newly launched satellite that for the first time will measure the Greenland and Antarctic ice sheets, to monitor melting as the world warms.
Although full meltdowns would take centuries, runoffs could raise the seas by dangerous inches in the coming decades.
“We have no idea how the ice sheets will actually respond. Do we really want to roll the dice?” asked Harvard’s Daniel Schrag, an expert on Earth’s ice ages.
The dice may already be rolling.
Oceanographers report that the North Atlantic is growing less salty because of melt runoff and increased precipitation. This may be ominous: It’s the sinking of heavier, saltier water that draws warmer surface waters from the south and keeps the climate, especially northern Europe’s, warmer than otherwise. A slowing of that ocean “conveyor” could drive down northern temperatures.
This uncertain threat of a regional “ice age” was featured in an internal Pentagon report in October, subtitled “Imagining the Unthinkable.”
Describing a “plausible” though “not most likely” scenario, it said abrupt climate change could stir conflict by prompting mass migrations in search of shelter and food.
The extreme vision disturbed climatologists. “Irresponsible,” one said privately. But some hoped that a Pentagon warning might arouse concern in Washington.
“Maybe it’s time for science fiction,” Schrag said. “The science is not exciting people.”
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(BEGIN TEXT OF INFOBOX)
Warming effects
A look at apparent “greenhouse gas” effects reported by scientists and other observers:
Oceans: Seas rose throughout the 20th century and, over the last decade, at a rate of one-tenth of an inch per year. Levels rise because water expands as it warms and melting ice from continents.
Islands: Islanders in the Pacific and elsewhere report steady erosion of shorelines from rising seas. Some small islands are gone.
Arctic: In late summers, Arctic Ocean ice is believed to be only 60% as thick as it was a few decades ago. And it is believed to extend over 10%-15% less area.
Animals: Seals, polar bears and other northern animals could be severely affected by shrinking Arctic ice. Biologists find polar bears are losing weight because of reduced hunting time on ice.
Tundra: Spring temperatures in the Alaskan Arctic were as much as 7 degrees warmer in 2000 than in 1971. Permafrost is melting, buckling roads and damaging other infrastructure. Shrubs have moved into treeless areas.
Glaciers: There was widespread retreat of mountain glaciers in non-polar regions during the 20th century. Only 27 of 150 glaciers remain in Montana’s Glacier National Park.
Snow: Global snow cover is believed to have decreased by 10% since satellite observations began in the 1960s.
Spring: The season is arriving earlier, especially in the Northern Hemisphere. This lengthens the growing season but also summer, threatening to dry out vegetation. In California, earlier snowmelt runoff will disrupt water supplies.
Drought: British climatologists conclude that an increase in drought in southern Africa in the last 20 years is probably linked to climate change.
Hurricanes: The first recorded South Atlantic hurricane struck Brazil in March. Computer models had suggested tropical storms would first appear over those seas with global warming.
Source: Associated Press
Los Angeles Times
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Fact and Fiction on Climate
Common misconceptions about climate change:
A scientific debate rages over global warming.
Fact: There’s no question that the Earth has warmed in recent decades. Government and professional climate-science groups say man-made “greenhouse gases” are contributing to the warming -- probably causing most of it, according to a U.S. National Academy of Sciences panel and the U.N.-organized Intergovernmental Panel on Climate Change). The scientific discussion focuses on how fast and how high temperatures will rise -- depending on what’s done to counter warming -- and on the impact.
Satellites show global cooling, not warming.
Fact: Satellite readings once seemed to disagree with ground readings about warming. But a longer satellite record and more careful analysis of earlier readings have largely closed that gap.
A planet warmer by 2 degrees Fahrenheit doesn’t sound bad.
Fact: Scientists’ 2-degree prediction is a minimum and an average encompassing higher extremes in certain regions, seasons and times of day. Much damage would come indirectly from rising seas, drying out of some areas, heavier rains in others and similar disruptions.
The sun’s variability is the biggest cause of climate change.
Fact: The sun does “flicker,” but the U.N. panel says solar variability has made only a small contribution to global warming over the past century.
Recent warming is a natural rebound from the European “Little Ice Age.”
Fact: The U.N. panel says the unusually swift and lengthy warming of the 20th century “cannot simply be considered as a recovery from the ‘Little Ice Age’ of the 15th to 19th centuries.”
Warming is good because it will save us from a new Ice Age.
Fact: The artificial gases already in the atmosphere are far more than needed to hold off another ice age.
A melting Arctic ice cap won’t raise seas; ice melting in a glass doesn’t raise the water level.
Fact: Oceans are rising because of melt runoff from glaciers, the Greenland ice sheet and other ice on land, not in the sea. The Arctic Ocean’s sea ice is already displacing water and so, like ice cubes in a glass, won’t raise sea levels as it melts.
Source: Associated Press
Los Angeles Times
