editor’s note: Also in other news services. But not a lead story. SS


Carbon dioxide in the atmosphere exceeds 400 parts per million for first time since researchers began tracking the data in 1958.

The amount of carbon dioxide in the atmosphere surpassed a threshold not seen for 3 million years, exceeding 400 parts per million for the first time since researchers began tracking the data.

The main greenhouse gas blamed for global warming averaged 400.03 parts per million at the US National Oceanic and Atmospheric Administration’s Mauna Loa monitoring station in Hawaii on May 9, the agency said yesterday.

The level is considered a landmark by scientists and environmentalists, who say carbon emissions caused by burning fossil fuels are warming the planet and must be reined in before they cause irreversible changes to weather, sea levels and Arctic ice cover. NOAA’s data stretches back to 1958.

“We are in the process of creating a prehistoric climate that humans have no evolutionary experience of,” Bob Ward, policy director at the Grantham Research Institute on Climate Change and the Environment at the London School of Economics, said in a telephone interview.

The last time CO2 levels were this high was at least 3 million years ago, he said. Then, “temperatures were 2 to 3 degrees Celsius higher than pre-industrial times, the polar ice caps were much smaller, and sea levels were about 20 meters (66 feet) higher than today.”

Carbon dioxide can stay in the atmosphere for as much as a century, so levels now may cause warming for decades. The concentration has now increased by more than 40 percent from the pre-industrial mark of 280 parts per million, which is abbreviated to ppm.

The Mauna Loa data is important because it represents the longest set of continuous measurements of atmospheric concentrations of carbon dioxide. Charles David Keeling, a geochemist at the Scripps Institution of Oceanography, began taking readings there in 1958.

Keeling’s measurements provided the first physical evidence of the steady rise in CO2 in the atmosphere as a result of burning fossil fuels, confirming part of Swedish chemist Svante August Arrhenius’s theory from 1896 that burning fossil fuels may cause global warming.

The United Nations in 2007 said stabilizing the gas at 400 ppm to 440 ppm may lead to a temperature gain of as much as 2.8 degrees Celsius (5 degrees Fahrenheit). That’s at odds with the goal set out by climate treaty negotiators from more than 190 nations, who have agreed to shoot for limiting the temperature increase to 2 degrees. The global average has already risen by about 0.8 of a degree since pre-industrial times.

“We are heading in the wrong direction in terms of dealing with climate change,” David Nussbaum, chief executive officer of the environmental group WWF’s UK arm, said in an e-mailed statement. “There is limited time for governments to achieve the goal they have set themselves for agreeing a global deal that effectively tackles climate change.”

Negotiators at the UN talks are working toward agreeing on a global climate treaty in 2015 that would come into force from 2020. They’ll meet in Warsaw in November to lay the groundwork for those discussions.