Study blames Arctic ice decline on humans

Satellite data reveals that Arctic ice has declined by 37,000 square kilometers a year - a size that exceeds the combined areas of Maryland and Delaware.

December 7, 1999
Web posted at: 3:36 p.m. EST (2036 GMT)

By Environmental News Network staff

Humans are contributing more to the retreat sea ice in the Arctic than is natural climate change, according to a recent study.

For the first time, scientists have placed satellite-based observations of Arctic sea ice declines into a larger context, by using a computer model on climate change.

"For climate studies, you would ideally like to see hundreds of years of records, but satellite data only goes back a couple of decades," explains Claire Parkinson, a climatologist at NASA's Goddard Space Flight Center.

Satellite data between November 1978 and March 1998 reveals that that the Arctic ice overall has shown a downward trend of 37,000 square kilometers a year. That means a loss of an ice chunk that exceeds the combined areas of the states of Maryland and Delaware, Parkinson said.

While some scientists might argue that such a loss could occur naturally over time, Parkinson said results of the recent study strongly suggest that humans have played a large role in this decline.

To get a broader look, the research team used a global climate model from NOAA's Geophysical Fluid Dynamics Laboratory at Princeton University to see how unusual that trend might be in the context of 5,000 years. "The model stimulates what is going on in the ocean, atmosphere and land surface processes," Parkinson said.

Data from the model reveals that the likelihood of such a decline was less than two percent over the past 5,000 years, strongly suggesting that mother nature is not the one to blame.

The team also examined outputs from computer simulations that include greenhouse gas increases, tending to warm the atmosphere, and aerosol increases, tending to cool the atmosphere. The model results that included these human-induced changes show atmospheric temperature increases and a much better match with the observed sea ice decreases than the model results simulating natural variability. This suggests that the Arctic Sea ice decreases could partially be in response to increasing greenhouse gas levels during the second half of the 20th century.

The study, which includes research by a team of meteorologists, physicists and climatologists from the University of Maryland, Rutgers University, NOAA, the University of Illinois, NASA, the Hadley Center in Great Britain, and the Arctic and Antarctic Research Institute in Russia, appeared in the Dec. 3 issue of Science.

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