Study: More evidence Arctic's rapid warming isn't natural

By Renee Schoof | McClatchy Newspapers

WASHINGTON — The Arctic was cooling for 1,900 years because of a natural change in Earth's orbit until greenhouse gas accumulation from the use of fossil fuels reversed the trend in recent decades, according to a study published Thursday in Science magazine.

Scientists reconstructed the temperature record of the past 2,000 years using evidence from tree rings, ice cores and lake sediment, and found a steady cooling trend in Arctic summer temperatures of about 0.5 degrees Celsius — 0.9 degrees Fahrenheit — during the first 1,900 years. The cooling was caused by a slow natural cycle in Earth orbit that continues in this century.