A three-year, government-funded effort to track the movement of greenhouse gases throughout the atmosphere has yielded surprising results that could help improve the accuracy of climate models.

Researchers used a specially equipped plane for a series of pole-to-pole flights to measure the concentrations of greenhouse gases and black carbon particles at different altitudes, different locations and different times of the year.

Scientists hope to use the data to better map sources and sinks of heat-trapping substances, including carbon dioxide, methane and black carbon.

"The program was intended to take a cross-section of the atmosphere, like you would slice through an orange and look at a cross-section of it," said lead researcher Steven Wofsy, a professor of atmospheric and environmental science at Harvard University. "This is actually something we haven't had up until now."

Scientists have long used ground-based monitoring stations, like the federal observatory at Mauna Loa, Hawaii, to track greenhouse gas concentrations close to Earth's surface. More recently, they have developed satellites that can track carbon dioxide concentrations from space.

But Wofsy said the measurements his team collected using a Gulfstream V jet provide the most precise portrait of greenhouse gas movement through the lower levels of the atmosphere -- anywhere from 500 to 47,000 feet above the Earth's surface.

"It's like looking a chest X-ray from the '60s compared to a CAT scan today," Wofsy said of the data.

Significant methane levels found in Arctic

The project, known as "HIPPO," is scheduled to wrap up Friday, when the plane -- owned by the National Science Foundation and operated by the National Center for Atmospheric Research -- lands in Anchorage, Alaska.

Sifting through the data it has collected over five long-haul flights will take several years, Wofsy said. But the project has already yielded some surprising results for researchers who study how greenhouse gases move through the atmosphere.

That includes the discovery that surface waters in the open Arctic Ocean are releasing heat-trapping methane gas into the atmosphere at a "significant" rate as the region's sea ice recedes, Wofsy said.

It's not clear where the methane is coming from, but the HIPPO measurements suggest the amount released by the ocean is "of sufficient size to be important globally," he added.

Britton Stephens, an NCAR scientist and the project's co-principal investigator, said HIPPO flights have collected the first large-scale measurements of carbon dioxide and oxygen cycling into and out of surface waters of the Southern Ocean. Microscopic ocean plants pull CO 2 out of the atmosphere to produce energy by photosynthesis, a process that also releases oxygen into the atmosphere.

"Half of all the CO 2 we emit is taken up by land plants and oceans," he said. "It turns out that if you want to predict future climate, the largest uncertainty is what people will do. The second source of uncertainty is what plants and oceans will do."