"Sound Science," Common Sense & Global Warming

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For anyone who still needs “sound science” about global warming, here’s a small sampler: Temperatures are rising. James Hansen and colleagues of New York City’s Goddard Institute observed that during 2001, global temperatures averaged the second highest in recorded history (after roughly 1865), exceeded only by the El Nino year of 1998. “The global warmth of 2001 is particularly meaningful because it occurs at a phase of the Southern Oscillation in which the tropical Pacific Ocean is cool,” Hansen and colleagues wrote in a letter to Science. The first three months of 2002 were the warmest on the instrumental record, as a new El Nino took shape in the Pacific Ocean off the western coast of South America.

“Human activity has raised Earth’s surface temperature during the last 130 years,” according to a study published during January 2001 by the Journal of Geophysical Research. Robert Kaufmann of Boston University’s Center for Energy and Environmental Studies and David Stern of the Australian National University’s Centre for Resource and Environmental Study analyzed historical data between 1865 and 1990.

Using the statistical technique of cointegration, the scientists compared several factors (including greenhouse-gas levels, human sulfur emissions, and variations in solar activity) with global surface temperature in both the northern and southern hemispheres. Cointegration techniques are not confused by variables that tend to increase or decrease over time or contain some poor measurements. This was the first study to make a statistically meaningful link between human activity and temperature, independent of climate models, Kaufmann said.

“The countervailing effects of greenhouse gases and sulfur emissions undercut comments by climate change skeptics, who argue that the rapid increase in atmospheric concentrations of greenhouse gases between the end of World War II and the early 1970s had little effect on temperature,” said Kaufmann. During this period, Kaufmann said, “the warming effect of greenhouse gases was hidden by a simultaneous increase in sulfur emissions. But, since then, sulfur emissions have slowed, due to laws aimed at reducing acid rain, and this has allowed the warming effects of greenhouse gases to become more apparent.”

Warming has been most rapid in the polar regions. At Sachs Harbour on Banks Island in the high Arctic, mosquitoes and beetles are now common sights where they were unknown a generation ago. Sea-ice is thinner and now drifts far away during the summer, taking with it the seals and polar bears upon which the village’s Inuit residents rely for food.

In the winter, sea-ice often is thin and broken, making travel dangerous for the most experienced hunters. In the fall, storms have become more frequent and more violent, making boating difficult. Thunder and lightning have been seen for the first time, arriving with another type of weather that is new to the area, dousing summer rainstorms. “We have no other sources of food, the people in my community are completely dependent on hunting, trapping, and fishing,” said Rosemarie Kuptana, a resident of Banks Island’s only town, Sachs Harbour. “We have no means of adapting to a different environmental reality, and that is why our situation is so critical.”

“When I was a child, I never heard thunder or saw lightning, but in the last few years we’ve had thunder and lightning,” said Kuptana. “The animals really don’t know what to do because they’ve never experienced this kind of phenomenon.  We don’t know when to travel on the ice and our food sources are getting further and further away,” said Kuptana. “Our way of life is being permanently altered.”

Until February 2001, snow was in short supply across much of Alaska. For several weeks, unusual rain soaked Anchorage region. The snowless tundra along Norton Sound, near the end of the 1,760-kilometer Iditarod race trail, was so bare in December that it caught fire. Sufficient snow to hold the race had fallen by March, however, when the race is held. During training for the race in the Matanuska-Susitna Valley 40 miles north of Anchorage, much of the ground was bare. The trails were so icy that dogs risked injury.

In Antarctica, several large ice sheets have crumbled into the ocean during the last few years. Glaciologists Eric Rignot and Stanley S. Jacobs have been studying the physical mechanisms behind accelerating melting of Antarctic ice. They reported in Science, June 14, 2002, that “As continental ice from Antarctica reaches the grounding line and begins to float, its underside melts into the ocean. Results obtained from satellite radar interferometry reveal that bottom melt rates experienced by large outlet glaciers near their grounding lines are far higher than generally assumed.”

Furthermore, Rignot and Jacobs wrote, “The melting rate is positively correlated with thermal forcing, increasing by 1 meter per year for each 0.1 degree C. rise in ocean temperature. Where deep water has direct access to grounding lines, glaciers and ice shelves are vulnerable to ongoing increases in ocean temperature.” If Antarctica is melting around the edges (the same pattern has been reported in Greenland), why are interior Antarctic temperatures dropping? Such reports have become grist for anti-warming skeptics in recent months. One of the scientists who brought these reports to light has expressed a sense of irritated concern that many of the media have blown his findings out of proportion vis-à-vis the general debate on global warming.

Slawek Tulaczyk of the University of California at Santa Cruz told Keay Davidson of the San Francisco Chronicle (February 4, 2002) that press reports had left him “increasingly frustrated” by sometimes-careless media coverage of the global warming issue. Tulaczyk and Ian Joughin of the Jet Propulsion Laboratory in Pasadena reported in the January 18, 2002 issue of Science that the movement of the glacial Ross ice streams appears to be slowing, allowing the ice to thicken.

In another recent study, 13 scientists reported in the January 13, 2002 issue of Nature that while other continents have warmed to record-high temperatures in recent years, most of the Antarctic surface has cooled since 1966. Some editorial writers assumed that if Antarctica is getting cooler, then maybe the whole planet is cooling, too. “Is Another Ice-Age On the Way?” asked an editorial in the Rocky Mountain News.

A headline over an editorial in the San Diego Union-Tribune minced no words about it: “Scientific findings run counter to theory of global warming.” The editorial sarcastically asked: “Oh dear. What will the doomsayers say now? How will they explain away yet two more scientific studies that clearly contradict the global warming orthodoxy?” A headline in the National Post, a Canadian newspaper, declared: “Antarctic ice sheet has stopped melting, study finds.”

“Some media mistakenly equated the phenomenon studied by Joughin and Tulaczyk—a change in ice flow rates—with ice melting rates. The mistake contributed to the erroneous belief that the studies constituted, as it were, scientific ‘tests’ of the global warming theory,” wrote Davidson.

Contrary to some news reports, “the ice-sheet growth that we have documented in our study area has absolutely nothing to do with any recent climate trends,” Tulaczyk said. “I keep repeating to journalists that climate science is much like economics. Both deal with complex systems,” Tulaczyk observed. “Just as a single stock going up or down cannot be interpreted as a reliable indicator of economic recovery or collapse, we have to accept the occurrence of contradictory trends in the global climate.”

Contrary to these and other newspaper reports and opinions, “Global warming is real and happening right now,”  Peter T. Doran of the University of Illinois at Chicago, lead author of the Nature paper told Davidson. Doran said the cooling trend in Antarctica appears to be a surprising, regional exception to the overall planetary warming.

Doran emphasized that his team’s report in Nature does not change the nature of global warming in any significant way. Roughly half the Antarctic continent is still warming, even given the new reports, as is most of the rest of the planet. For example, the Antarctic Peninsula’s Larsen Ice Shelf has warmed 2.5 degrees Celsius during the last half century, as it disintegrates into the ocean. The Antarctica Peninsula (stretching northward toward South America) has been warming very rapidly, about 5 degrees over the past 50 years, 10 times the global average, matching temperature rises in Alaska.

The Antarctic cooling may stem from changes in wind patterns. An explanation of this apparent paradox may lie in a climactic “master switch” over the high southern latitudes, a circular wind pattern (the “Antarctic Oscillation”) that is being driven faster by the depletion of stratospheric ozone.

Writing in the May 3, 2002 issue of Science, David W. J. Thompson, a professor of atmospheric science at Colorado State University, and Dr. Susan Solomon, a senior scientist at the National Oceanic and Atmospheric Administration in Boulder, Colorado, assert that ozone depletion over the Antarctic may help explain both contradictory trends. “Ozone seems to be capable of tickling the Southern Hemisphere patterns,” Thompson said.

Thompson and Solomon link cooling in the stratosphere induced by depletion of ozone levels to acceleration of the winds. “During the summer-fall season,” Thompson and Solomon have written, “The trend toward stronger circumpolar flow has contributed substantially to the observed warming over the Antarctic Peninsula and Patagonia and to the cooling over eastern Antarctica and the Antarctic plateau.”

Thompson and Solomon show that a vortex of winds blowing around Antarctica that traps cold air at the South Pole have strengthened in the past few decades, keeping the cold air even more confined. The Antarctic peninsula lies outside the wind vortex and thus escapes the cooling effect. Ozone depletion may be a key causal factor in strengthening the wind pattern, according to Thompson and Solomon. “That’s where we speculate,” Dr. Thompson said, “and the emphasis is on the word ‘may’.”

Maryland’s population of Baltimore orioles, long in decline, could vanish altogether late this century because of dramatic changes in migration patterns and declining habitats strongly influenced by global warming. A study by the National Wildlife Federation and the American Bird Conservancy suggests that global warming  effects may be driving state birds from Maryland and a half-dozen other states.

According to the report, rising temperatures are changing migration patterns and threatening some well-known birds’ ability to survive. Iowa and Washington state would eventually see their last American goldfinch, as New Hampshire would fall outside the range of the purple finch. California quail would skip that state and Massachusetts’ black-capped chickadee would vanish. Georgia would lose the brown thrasher and Maryland would fall outside the range of the Baltimore oriole, according to the study.”

Rising water temperatures caused by global warming also could drive several cold-water species of trout and salmon from many U.S. waterways, by the end of the century. In many areas, these fish already are living at the margin of their temperature tolerance. Defenders of Wildlife and the Natural Resources Defense Council assert that by the end of the century, many salmon and trout will be restricted to the northernmost sections of the United States. The groups’ analysis covers four species of trout—brook, cutthroat, rainbow, and brow—and four species of salmon—pink, coho, chinook, and chum. Researchers looked at air and water temperature data from more than 2,000 sites across the U.S.

“Wild trout and salmon populations are already stressed by factors such as loss of habitat to development, competition with hatchery fish, invasive exotic species, and more. Now we must add climate change to the list of challenges they face,” said Mark Shaffer, senior vice president at Defenders of Wildlife. “If we don’t address the cumulative impact of all these factors, we will see more of these populations switching from a recreational resource to being listed as threatened or endangered.”

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Bruce E. Johansen, a professor of Communication at the University of Nebraska at Omaha, is the author of The Global Warming Desk Reference (Greenwood Press, 2001).