VOA慢速英语--自20世纪80年代以来，美国圣诞节下雪的几率下降

Research of 40 years of December 25 United States snow measurements shows that less of the country now has snow for Christmas than in the 1980s. And snow that does fall does not measure up to past depths.

Federal weather records show that the average December temperature in the continental¹ U.S. was a little below freezing from 1981 to 1990. From 2011 to 2020, it was up to an average just under 2 degrees Celsius².

Research done by the University of Arizona for the Associated Press shows that from 1981 to 1990, on average, almost 47 percent of the country had snow on the ground Christmas Day. It showed that the average depth was 8.8 centimeters. From 2011 to 2020, Christmas snow cover was down to 38 percent, with an average depth of 6.8 centimeters.

The change is very clear for the area that runs from Baltimore, Maryland, to Denver, Colorado, and a few hundred miles farther north to Detroit and Chicago. The Arizona information shows that the Christmas snow cover average went from nearly 55 percent in the 1980s to just above 41 percent now. Average snow depth fell from 8.8 centimeters to 6 centimeters.

Xubin Zeng is an atmospheric³ scientist at the University of Arizona who ran the information. Zeng said the numbers are small enough that it is difficult to tell if this is a meaningful trend and, if so, if climate change or natural weather differences is the cause.

Still, Zeng said the reduction of snow on Christmas lines up with climate change.

Climate scientist Imke Durre said places where there is at least a ten percent chance for snow on Christmas moved north with the new normal. The nation's capital, Washington D.C., went from ten percent to seven percent.

"The movement of that line is consistent⁴ with a warmer December," Durre said. New York, Philadelphia and Concord⁵, New Hampshire, recorded small increases in chances of Christmas snow on the ground.

David Robinson is a climate scientist at Rutgers University in New Jersey⁶. He said the university has information based on satellite imagery that goes back to 1966. It shows continental U.S. snow in the last week of December has a small increase, not decease.

"There's no trend. You just don't see it," Robinson said.

Often people in their 60s and 70s think there are fewer Christmases with snow, he added, because the 1960s had more than the usual Christmases with snow.

Meteorologists, or scientists who study the weather, said that temperature changes snowfall in two different ways. In warmer borderline areas, warmer air turns snow into rain. But in cooler more northern areas, where higher temperatures are still below freezing, warmer temperatures mean more snow. This is because warmer air holds more water which comes down as snow.

Several meteorologists warned about finding trends in large amounts of information where both temperature and rain or snowfall are influences.

Victor Gensini is a meteorology professor at Northern Illinois University. He said even with those issues, fewer Christmases with snow seem to be linked with warmer temperatures from climate change.

Words in This Story

trend – n. a general direction of change: a way of behaving o proceeding⁷ that is developing and becoming more common

consistent – adj. in agreement with something

professor – n. a teacher especially of the highest rank at a college or university

1 continental   

adj.大陆的，大陆性的，欧洲大陆的

参考例句：

• A continental climate is different from an insular one.大陆性气候不同于岛屿气候。
• The most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。

2 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

3 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。

4 consistent   

adj.坚持的，一贯的，一致的，符合的

参考例句：

• He has been a consistent friend to the Chinese people.他是中国人民始终如一的朋友。
• His action is always consistent with his words.他始终言行一致。

5 concord   

n.和谐；协调

参考例句：

• These states had lived in concord for centuries.这些国家几个世纪以来一直和睦相处。
• His speech did nothing for racial concord.他的讲话对种族和谐没有作用。

6 jersey   

n.运动衫

参考例句：

• He wears a cotton jersey when he plays football.他穿运动衫踢足球。
• They were dressed alike in blue jersey and knickers.他们穿着一致，都是蓝色的运动衫和灯笼短裤。

7 proceeding   

n.行动，进行，(pl.)会议录，学报

参考例句：

• This train is now proceeding from Paris to London.这次列车从巴黎开往伦敦。
• The work is proceeding briskly.工作很有生气地进展着。