text: After examining climate data extending back nearly 100 years, a team of Government scientists has concluded that there has been no significant change in average temperatures or rainfall in the United States over that entire period.
  While the nation's weather in individual years or even for periods of years has been hotter or cooler and drier or wetter than in other periods, the new study shows that over the last century there has been no trend in one direction or another.
  The study, made by scientists for the National Oceanic and Atmospheric Administration was published in the current issue of Geophysical Research Letters. It is based on temperature and precipitation readings taken at weather stations around the country from 1895 to 1987.
  Dr. Kirby Hanson, the meteorologist who led the study, said in a telephone interview that the findings concerning the United States do not necessarily ''cast doubt'' on previous findings of a worldwide trend toward warmer temperatures, nor do they have a bearing one way or another on the theory that a buildup of pollutants is acting like a greenhouse and causing global warming. He said that the United States occupies only a small percentage of Earth's surface and that the new findings may be the result of regional variations.
  Readings taken by other scientists have suggested a significant warming worldwide over the last 100 years. Dr. James E. Hansen, director of National Aeronautic and Space Administration's Institute for Space Studies in Manhattan, has reported that average global temperatures have risen by nearly 1 degree Fahrenheit in this century and that the average temperatures in the 1980's are the highest on record.
  Dr. Hansen and other scientists have said that that there is a high degree of probability that this warming trend is associated with the atmospheric buildup of carbon dioxide and other industrial gases that absorb and retain radiation.