Earth's average surface temperature in 1998 is the highest by far since people began to measure it with thermometers in the mid-19th century, the World Meteorological Organization reported yesterday.

The United Nations agency said 1998 will be the 20th year in a row that the globe's surface has been warmer than its recent long-term average, which is the average for 1961 through 1990.

Seven of the 10 warmest years on record have occurred since 1990 and the other three occurred after 1983. Most recently, new monthly high-temperature records were set in each of the 18 consecutive months ending in October 1998.

According to the new figures, the average global temperature this year will turn out to be about 58 degrees Fahrenheit, a full degree warmer than the 1961-1990 average.

"This number's amazing," said Dr. Philip Jones, a climatologist at the University of East Anglia in England, speaking of a field in which records are normally set in fractions. Jones provided much of the information for yesterday's announcement.

Based on studies of such indirect evidence as the annual rings of trees, Jones has been saying for some time that he believes 1998 to be not only the warmest year in the thermometer record, but also the warmest year of the millennium now ending.

While there are dissenters who believe the warmer climate can be explained by normal variation, the dominant view among climate scientists is that at least some of the warming trend is a result of emissions of heat-trapping waste industrial gases.

A number of scientists have said they believe the world is likely to be cooler in 1999 and possibly 2000 as well. The reason, they said, is that a fair measure of the warming in 1998 can be attributed to the effects of El Nino, which both warms the global atmosphere and disrupts worldwide weather patterns.

The United States has often lagged in the warming trend.

But this year, according to an analysis by the Goddard center in New York, North America led the warming trend, experiencing its warmest year in the past four decades. El Nino was said to be largely responsible, since its impact on North America is stronger than in many other places.

Temperatures well above the surface, as measured from Earth satellites, have not usually shown the same rise as the surface temperatures, though they do show a slight warming.

This year, however, temperatures from the surface to an altitude of about four miles were nearly a degree above average. The magnitude of this rise has also been attributed largely to El Nino.

Pub Date: 12/18/98