Getting Warmer?

Is the U.S. climate getting warmer? U.S. meteorologists, observing and charting the weather with growing exactitude over the past 20 years, are no closer to agreement on the question than their predecessors of a century ago. Last week a Washington convention of the American Meteorological Society heard strong evidence to favor the warmup theory.

Dr. Richmond T. Zoch of the Weather Bureau reported that Washington temperature records, begun in 1862, show that Washington's climate had warmed by about 3.5DEG F. since then. Harvard's Dr. John H. Conover backed Dr. Zoch. He said that a 100-year record kept at the Blue Hill Meteorological Observatory and at nearby Milton Centre, Mass., showed a 3DEG increase. Dr. Conover had gone to the trouble of finding the early Victorian thermometer used in 1849 and checking it against modern instruments, made allowances for differences. In further support of his position he pointed out that the Blue Hill records were made in a large state park well outside Boston. So they were immune to the heating effect attributed to great modern cities.

The temperature changes seem small, but 3DEG is nearly half the average difference between May and June in New York City. The changes may account for the observed fact that many parts of the U.S. have been having more frost-free seasons and frost-free days.

Not all meteorologists admit that the increases are real. Methods of measuring temperature, they say, have varied too much in the last 100 years. Climatologist Herbert Thorn of the Weather Bureau pointed out that the Washington records were taken in many places and by many different methods. He hopes to settle the matter by analyzing the complete weather records made in New York City's Central Park since 1869.

Dr. Ivan R. Tannehill, also of the Weather Bureau, is less skeptical. He thinks the U.S. climate is really getting warmer and probably drier too. His tentative explanation: a slow increase in radiation from the sun.

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