Worldwide temperatures last year climbed to their highest levels since record-keeping began, continuing a steady, upward march that government meteorologists described as powerful evidence that people are changing Earth's climate.
The year 1997 was not only the warmest on record, but it was part of exceptionally sultry decade that witnessed nine of the 11 hottest years this century, scientists of the National Oceanic and Atmospheric Administration said yesterday.
The new data are likely to strengthen the conviction among the many scientists who believe man-made greenhouse gases are contributing to a potentially disastrous warming of Earth's atmosphere. They also could provide a boost to the Clinton administration as it tries to secure Senate approval of the global climate treaty approved by 159 countries last month in Kyoto, Japan.
"For the first time, I feel confident in saying there's a human component" causing the rising temperatures, Elbert W. Friday Jr., a meteorologist and NOAA's associate administrator for oceanic and atmospheric research, told a news conference.
Although an international body of climate scientists concluded two years ago that humans are having a "discernible influence" on Earth's climate, Friday said mankind's imprint is becoming clearer with each year's measurements. At the same time, the likelihood that the recent rise in temperature is a strictly natural phenomenon is becoming increasingly remote, he said.
"We've had three more years of data, and it's all in the same direction," he said. "It all shows the same thing."
Not all scientists agree. On the same day NOAA released its findings, a pair of Alabama scientists reported that the planet actually cooled slightly last year. The University of Alabama-Huntsville report was based on data from satellites that measure atmospheric temperatures at nearly five miles above Earth's surface.
"From the satellite's point of view it was a very normal year," said John Christie, an associate professor of atmospheric science. While most measurements point to an overall warming trend over the past century, Christie said, scientists don't yet know enough about Earth's highly complex climate to draw conclusions.
But NOAA said its land-based measurements more accurately reflect conditions at Earth's surface, where people live, work and grow their crops. Its findings are nearly identical to those of the British Meteorological Office, which last month projected that 1997 would go down as the warmest year since scientists began systemically tracking the weather in mid-19th century.
Boosted by exceptionally warm temperatures in December, 1997's global average temperature was at 62.45 degrees Fahrenheit -- three-quarters of a degree higher than the "normal" average for the past 30 years, and 0.15 degrees warmer than the previous record high set in 1990, NOAA said.
NOAA's weather rankings are based on a global "index" that reflects measurements of ocean water temperatures as well as data from official weather stations on land. Adjustments were made to offset artificial increases in temperature that could result from urban development near weather stations, NOAA officials said.
Temperatures got a boost from the El Nin~o weather phenomenon that has caused unseasonable warming in parts of the Pacific. But NOAA scientists said 1997 would have gone into the history books anyway.
"Whether it would have been the warmest year this century is a matter of debate, but it certainly would have been in the top 10," said Tom Karl, senior scientist at NOAA's National Climate Data Center in Asheville, N.C.
The global warming treaty approved in Japan last month would require the United States and other industrialized countries to sharply reduce emissions of carbon dioxide, methane and other gases that have been building up in the atmosphere since the start of the industrial revolution. Further increases in these heat-trapping "greenhouse" gases are expected to gradually raise global temperatures by between 1.8 and 6.3 degrees by 2100 -- a rapid jump by geological standards that could boost global sea levels and disrupt agriculture in many parts of the world, NOAA scientists say.
The Clinton administration is not expected to submit the Kyoto treaty for Senate ratification until at least 1999. But in the meantime, it is seeking agreements with major industries for voluntary reductions in air pollution.
Yesterday, Vice President Gore announced a partnership with major electronics companies to promote increased energy efficiency in televisions and videocassette recorders. Under the agreement, companies would seek voluntarily to reduce the amount of electricity their appliances consume when turned off. Currently, the electricity used by idle TVs and VCRs in this country adds about $1 billion a year to consumer power bills, administration officials said.
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