The readings at this 2-mile-high station show a troubling upward curve as the world counts down to crucial climate talks: Global-warming gases are building in the atmosphere at record levels from emissions that match scientists' worst-case scenarios.
Carbon-dioxide concentrations this fall are hovering at around 385 parts per million, on their way to a near-certain record high above 390 in the first half of next year, at the annual peak.
"For the past million years, we've never seen 390. You have to wonder what that's going to do," said physicist John Barnes, the observatory director.
One leading atmospheric scientist, Stephen Schneider, sees "coin-flip odds for serious outcomes for our planet."
Far from this mid-Pacific government observatory, negotiators from 192 nations gather in wintry Copenhagen, Denmark, next month to try to agree on steps to head off the worst of the climate disruptions that researchers say will result if concentrations hit around 450 parts per million -- in 30 years at the current rate. Some say the world has already passed a danger point, at 350 ppm, and must roll back.
Today's emissions curve is tracking the worst case among seven emissions scenarios set out in 2001 by the U.N.'s Intergovernmental Panel on Climate Change (IPCC), British climatologists reported in September.
The U.N. expert group projects that such a path would raise global temperatures between 4.3 and 11.5 degrees F by century's end. That would come on top of a global temperature increase of about 0.6 degrees Celsius (1 degree Fahrenheit) in the past century, a warming trend that the authoritative IPCC says is mainly due to the buildup of carbon dioxide and other greenhouse gases.
Such warming will shift climate patterns, cause more extreme weather, spread drought and floods to new areas, kill off plant and animal species, and cause seas to rise from heat expansion and the melting of land ice, the IPCC says.
"Changing several degrees may not seem like much, but we're just changing things too fast," Barnes said. "So the consequences could well be drastic."
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