Last 25 years warmest on Earth since 1600

The last few decades were the warmest on Earth in the past 400 years, and may well have been warmer than any comparable period since the Middle Ages, U.S. scientists reported on Thursday.

Photo: Last 25 years warmest on Earth since 1600

In a separate study, climate experts blamed global warming for much of the hurricane-fueling rise in temperatures in the North Atlantic last year, when there were a number of devastating hurricanes, including Katrina.

In a new report by the National Research Council, researchers said they were highly confident the mean global surface temperature was higher in the past 25 years than any comparable period during the previous four centuries, reports Reuters.

According to Forbes, other new research showed that global warming produced about half of the extra hurricane-fueled warmth in the North Atlantic in 2005, and natural cycles were a minor factor, according to Kevin Trenberth and Dennis Shea of the National Center for Atmospheric Research, a research lab sponsored by the National Science Foundation and universities.

The academy had been asked to report to Congress on how researchers drew conclusions about the Earth's climate going back thousands of years, before data was available from modern scientific instruments. The academy convened a panel of 12 climate experts, chaired by Gerald North, a geosciences professor at Texas A&M University, to look at the "proxy" evidence before then, such as tree rings, corals, marine and lake sediments, ice cores, boreholes and glaciers.

Combining that information gave the panel "a high level of confidence that the last few decades of the 20th century were warmer than any comparable period in the last 400 years," the panel wrote. It said the "recent warmth is unprecedented for at least the last 400 years and potentially the last several millennia," though it was relatively warm around the year 1000 followed by a "Little Ice Age" from about 1500 to 1850.