As Arctic warms, scientists rethink culprits

In its effort to curb global warming, a three-year-old international pact aimed at cutting carbon-dioxide emissions may be focusing on the wrong chemical villain - at least in the short term.

As the 1997 Kyoto accords bog down - primarily over disagreements within industrialized countries over how to dramatically reduce carbon-dioxide (CO2) emissions by 2012 - new research indicates that the world can make just as much progress by limiting other greenhouse gases, such as methane, ozone, and chlorofluorocarbons.

Findings by James Hanson, a NASA scientist whose Jeremiah-like warnings about global warming helped lay the foundation for the Kyoto Protocols, and several colleagues show that controlling these other gases first may be a more effective - and in the short run, more painless - approach to slowing climate change.

Though less abundant than CO2, these other gases have combined to warm the atmosphere just as much as all the carbon-dioxide human activities of the past 150 years, the scientists say. Their conclusion: Activities that produced these other heat-trapping gases have been "the primary drive for climate change in the past century."

The study, published in the current issue of the Proceedings of the National Academy of Science, comes as the United States and 100 Kyoto signatories prepare for meetings over the next few months to iron out unresolved issues in the pact. One sticking point centers on achieving the goals without sending industrial nations - the world's major C02 producers - into an economic tailspin.

The study also coincides with growing evidence that Earth's climate is indeed changing in ways scientists have predicted - particularly in the Arctic, which is thought to be a bellwether region.

*This month, a team of researchers from four US universities published a survey of polar environmental studies conducted during the past 30 years. Among its findings: Evidence suggests that temperatures in the Arctic are at their warmest in 400 years.

*Last week, passengers on a Russian icebreaker reported finding a mile-wide stretch of open water - in place of the ice cap - at the North Pole.

In and of itself, that is no surprise, although it dramatizes the global-warming phenomenon. "In an ice pack, there will always be some open water" this time of year - even at the North Pole, says Donald Perovich, who studies the links between polar ice and climate at the US Army Corps of Engineers' Cold Regions Research and Engineering Laboratory in Hanover, N.H.

*The polar ice cap has lost 40 percent of its volume in the decades since 1958, according to a study issued in December. Polar researcher Drew Rothrock and colleagues compared ice soundings - taken by US Navy submarines between 1958 and 1976 - with soundings taken during scientific sub cruises from 1993 to 1997.

Researchers are concerned about warm Arctic temperatures and melting polar ice for several reasons.

Globally, the injection of cold, fresh water into the North Atlantic could slow the "conveyer belt" that shuttles waters between the North Atlantic and the equator. In the usual circulation pattern, currents bring cold, nutrient-rich water to the surface near the equator, warm it and convey it north, where it cools, freshens, sinks, and flows south again.

This circulation in the North Atlantic is a key driver behind currents that flow all the way into the Pacific. If it changes, the effects would be felt worldwide as fisheries changed locations and regional climate patterns shifted with the currents. British researchers have calculated, for example, that if the Gulf Stream were shut off - its terminus driven far enough south or its circulation slowed - average temperatures in Britain would drop 5 degrees Celsius. Norway's temperatures would fall 10 degrees.

Locally, the loss of ice cover means loss of habitat for many of the animals the Inuit rely on for food, as well as increased storminess as larger areas of the Arctic are exposed to evaporation. It also may stir international battles over navigation rights, as Canada's Northwest Passage remains ice-free for longer periods of time. Shipowners eager to save money and time may seek to route their freighters and tankers across northern Canada instead of through the Panama Canal.

Against this backdrop of politics, economic, and climate signals, Dr. Hanson and colleagues from Columbia and Rutgers Universities suggest that carbon dioxide hasn't been as influential in climate change as first thought. Newer analytical techniques and computer models have revised the researchers' assessment of the heat-trapping ability of non-CO2 greenhouse gases.

While the need to control CO2 remains, the quickest progress can be made by controlling non-CO2 gases.

Although methane, CFCs, and gases such as ozone and nitrous oxide are more potent greenhouse gases, they make up a smaller portion of the atmosphere than CO2 and hence should be easier to control.

The two largest sources of human-related methane come from rice fields and cattle. The team holds that changing irrigation and fertilization systems in rice fields and altering the diet of cattle will reduce methane emissions from those sources. In the process, lower methane levels should also reduce ozone in the lower atmosphere.

(c) Copyright 2000. The Christian Science Publishing Society