Studies show a hot North Pole

Nearly 55 million years ago, the North Pole seemed more like Florida than the icehouse it is now, with balmy temperatures averaging about 75 degrees Fahrenheit, cypress trees and swamps filled with alligators, three new studies show.

“It’s conclusive the Arctic was extraordinarily warm at this time period. This study provides some actual numbers,” said Mark Pagani, a geology professor at Yale University and a study author.

Mr. Pagani was part of a multinational expedition that traveled to the central Arctic two years ago and conducted research designed to determine just how hot it once was there. The explorers’ findings are published in this week’s issue of the journal Nature.

Scientists already knew that the Earth experienced a long period of what they described as “natural global warming” millions of years ago. They also knew that most of the Earth heated up about 55 million years ago, but there is uncertainty about why. Scientists speculated that the causes could be a methane gas release from the ocean, massive tree-burning or volcanic eruptions.

But before their on-the-scene polar research, Mr. Pagani and his team thought temperatures at the top of the world were cooler than anywhere else, about 52 degrees Fahrenheit.

They discovered that those estimates were low when they dug up core samples from deep beneath the floor of the Arctic Ocean.

“Core samples are the best time recorder of the Earth’s history,” Mr. Pagani said.

The samples, coupled with use of computer modeling and principles of thermal dynamics, convinced the team that the Arctic was “subtropical in nature” 55 million years ago.

While some reports have characterized the Arctic as a “tropical paradise” during the prehistoric time, Mr. Pagani points out that it probably had mosquitoes the size of a human head.

He said he and his colleagues are convinced that the dramatic spike in temperature at the North Pole was sparked by a massive amount of carbon dioxide in the atmosphere that accelerated the greenhouse gas effect.

Asked where the carbon dioxide originated, Mr. Pagani said, “There was a much higher background of carbon dioxide at that time.” In fact, levels then were four times greater than they are now, and the gas was “emitted by volcanoes.”

He said he knows that not everyone will agree with this theory and that some will argue that a methane discharge caused the sharp spike in heat.

“Methane is a very strong greenhouse gas, but it does not remain in the atmosphere long,” he said.

In contrast, Mr. Pagani said, carbon dioxide “builds up” in the atmosphere and can reside there for 100,000 years.

Another scientist involved in the research, Hans Brinkhuis of Utrecht University in the Netherlands, theorized that the Arctic became frigid and icy because of a prolific fern called Azolla, which began sucking up huge amounts of carbon dioxide about 50 million years ago.

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