Millennia of Arctic Cooling Came to Abrupt End in 20th Century

Greenhouse gases released by human activity have swiftly ended a millennia-long trend of cooling in the Arctic and may well halt the next cyclical descent into an ice age, according to a new study. The report — based on a study of glacial ice, lakebed mud, and tree rings that provide a decade-by-decade record of Arctic climate for the past 2,000 years — demonstrates that humankind is now pouring so many greenhouse gases into the atmosphere that we are interfering with ancient cycles of ice ages and inter-glacial periods that have occurred for millions of years. Writing in the journal Science, researchers reported that until 1900, the Arctic was cooling at a rate of half a degree Fahrenheit per millennium for the past 2,000 years. This was because of a natural cycle in which earth’s orbit is farther from the sun. But since 1900, the Arctic has warmed 2.2 degrees F, with 1998 to 2008 being the warmest decade in 2,000 years. This precipitous warming caused by heat-trapping greenhouses gases is not only melting Arctic Ocean ice and the Greenland ice sheet but, if not brought under control, may stave off the arrival of the next Ice Age, expected in roughly 20,000 years.