Dr. John Barnes is a scientist and station chief for the Mauna Loa Observatory atmospheric research facility in Hawaii. The observatory sits on the north flank of Mauna Loa volcano at an elevation of 11,141 feet above sea level. The facility has been studying atmospheric change since the 1950s.

Mauna Loa Observatory, Hawaii ? The readings at this 2-mile-high station show an upward curve as the world counts down to climate talks: Global warming gases have built up to record levels in the atmosphere, 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 Copenhagen, Denmark, next month to try to agree on steps to head off the worst of the climate disruptions 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, 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 1 degree Fahrenheit in the past century, a warming trend the 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 events, 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.”

The IPCC has urged industrialized countries to reduce global emissions by 25 to 40 percent below 1990 levels by 2020. As of 2007, they stood only 4 percent below 1990 levels, and the rest of the world continued pouring out more and more heat-trapping gases, chiefly from the burning of coal, gasoline and other fossil fuels.

Through this decade global emissions have grown by 23 percent. In 2008, almost three-quarters of the increase came from China, re-searchers reported last week. Other big contributors among developing countries were India, Saudi Arabia, Brazil, South Africa, South Korea, Indonesia, Iran and Mexico.

Experts see no sign of a slowdown.