"It supports the view of people who say there's a very big effect of pollution, even in the wintertime," Wofsy said.
To map the atmosphere, scientists are flying a specially equipped Gulfstream V jet, owned by the National Science Foundation and operated by Colorado-based NCAR.
The plane has a range of 7,000 miles, allowing researchers to traverse vast swathes of the Pacific without refueling. Extraordinarily powerful engines allow the jet to cruise at altitudes from 1,000 feet to 47,000 feet, into the lower stratosphere nearly nine miles up.
In contrast, a typical Boeing 767 has a range of about 4,000 miles and cruises at about 35,000 feet.
And while the jet started as a luxury corporate item, it is now anything but: the cabin is stuffed with pipes, pumps, filters, analyzers, sensors computers and other laboratory equipment. They have drilled holes through the fuselage so lasers could point up and down, added pods and intake valves, ditched the leather.
"We have the equivalent of a very expensive laboratory where we can sit behind our instruments as we're going along," Stephens said.
Scientists from NCAR, Harvard, the National Oceanic and Atmospheric Administration, the Scripps Intitution of Oceanography, the University of Miami and Princeton University will complete this week the first of five missions. They left Jan. 8, flying from Colorado to Alaska and the Arctic Circle, then south to New Zealand and Antarctica. Late this week they will return from Costa Rica to Colorado.
Four subsequent missions through mid-2011 will follow similar flight paths but at different times of the year, providing a range of seasonal snapshots of greenhouse gas emissions.
The research will help answer such questions as why atmospheric levels of methane, a potent greenhouse gas, have tripled since the Industrial Age and are on the rise again after leveling off in the 1990s. They will also answer how gases and particles in the atmosphere affect temperatures by influencing clouds or the amount of solar heat reaching the Earth's surface.
And by ramming their data, along with long-standing surface measurements, through computer models, they hope to expose the weaknesses of current projections.
"Some modeling approaches will simply fail," Wofsy said. "They won't be able to do this. That's what we're after here: We're confronting these global models with data."
And the experiment is also confronting scientists with a bit of perspective.
"It's quite an experience to fly in an airplane above the Arctic ice sheet, with moonlight illuminating it, and then a short time thereafter be above American Samoa and the lush tropical forest, and then a short time later be over New Zealand," Wofsy said. "It really gave a strong sense of the interconnection of the globe."
Douglas Fischer is editor of the Daily Climate. This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.