Gregory M. Lamb

New Efforts to Predict When Polar Ice Will Melt

The loss of sea ice in the Arctic may have reached a "tipping point" that could "trigger a cascade of climate change" reaching much farther south. As Arctic warming accelerates, polar waters could become ice-free by the turn of the century, or, under one scenario, as early as 2040.

These are among the conclusions of a new study published March 16 in the journal Science. The area of the Arctic covered by sea ice has been shrinking at least since 1979, when regular satellite observations began.

The report attributes the loss of ice, averaging about 38,000 square miles annually (an area about the size of Maine), to rising concentrations of greenhouse gases in the atmosphere, as well as to natural variability.

Says Mark Serreze, a senior research scientist at the University of Colorado's National Snow and Ice Data Center and the lead researcher on the report:

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