Air Date: Week of November 14, 1997

In this week's issue of the journal Science, a team of federal and university researchers report a dramatic rise in Arctic temperatures since the middle of the last century. They say the record only makes sense when the effects of industrial society are factored in. Living On Earth's Daniel Grossman reports.

Transcript

CURWOOD: Climatologists agree that the Earth's average temperature has gone up about 1 degree Fahrenheit in the last 150 years. But it's hard to determine exactly how much of this increase has been caused by human activities like burning fossil fuels, which release carbon dioxide. In this week's issue of the journal Science, a team of Federal and university researchers from the US and Canada reported a dramatic rise in Arctic temperatures since the 1850s, and they say the increase only makes sense when the effects of industrial society are factored in. Living on Earth's Daniel Grossman reports.

GROSSMAN: According to the researchers, this is the most comprehensive study of the ups and downs of temperature in the Arctic. The region holds special interest because there are few human settlements in this vast and sparsely- populated land to prevent accurate measurements of its climate, and because its ecosystem is believed to be especially fragile. There are few thermometer readings of the region before 1900. So scientists must infer earlier temperatures from natural records. The research team collected data from tree rings, ice cores, and lake sediments at 29 Arctic sites. They report that between 1840 and 1950 the pole warmed one and a half degrees Celsius, or about 3 degrees Fahrenheit, to the highest temperature in the last 400 years. And there's more. Ray Bradley heads the Geosciences Department at the University of Massachusetts at Amherst. He says for centuries, Arctic temperatures varied widely across the territory with some areas experiencing warm spells while others were cold. But --

BRADLEY: As we get into the middle of the 19th Century, all of the Arctic start to fall into step, and all of the Arctic starts to get warmer. So it's as though some factor began to force the Arctic into a common response.

GROSSMAN: That raises the question: could humans be that factor? Industrial society began ramping up just as the Arctic warming began. Jonathan Overpeck is a researcher at the National Oceanic and Atmospheric Administration and the study's lead author. He says natural phenomena like variations in the sun's output and volcanic activity, which produces sun- blocking gases, can cause changes on this scale. Such natural effects explain the Arctic warming until about 1920, but not later.

OVERPECK: That led us to conclude that there is something else, and the most logical and perhaps the only real contender is increases in greenhouse gases in the atmosphere, caused by human activity.

GROSSMAN: The researchers report that the warming coincided with retreating glaciers, melting permafrost, and changes to aquatic ecosystems. They say such transformations are worrisome as even greater temperature increases are forecast.

BRADLEY: This is just sorry to use this phrase but it's the tip of the iceberg in the context of what may take place in the future.

GROSSMAN: University of Massachusetts professor Ray Bradley. For Living on Earth, this is Daniel Grossman.