Science News — A major pollution-mapping program that ends September 9 has turned up startling trends in climate-warming gases and soot. The data it collected over the past five years from a National Science Foundation aircraft show the tropics periodically belch huge plumes of nitrous oxide — a potent greenhouse gas — into the upper atmosphere. Arctic measurements show that the recent record summer retreats of ice cover have allowed seas there to exhale unexpected amounts of methane, another potent greenhouse gas.
Then there’s soot. Parts of the supposedly pristine Arctic skies host dense clouds of these black carbon particles. During some flights, “We were immersed in essentially clouds of black carbon that were dense enough that you could barely see the ground,” recalls Stephen Wofsy of Harvard University, a principal investigator in the program. “It was like landing in Los Angeles — except that you were 8 kilometers above the surface of the Arctic Ocean.”
Until a few years ago, scientists interested in mapping global emissions of climate-altering pollutants had to rely on Earth-based sensors or satellites’ eyes on the skies. Neither could identify at what altitude the pollutants tended to congregate. They also missed many highly localized or seasonal plumes of natural pollutants.
That all changed when a federal-university research partnership got access to NSF’s research plane: HIAPER (for High Performance Instrumented Airborne Platform for Environmental Research). Throughout a number of periodic runs, this aircraft repeatedly swooped up and down — from 150 meters above Earth’s surface to heights sometimes exceeding 13.7 kilometers (45,000 feet). All along the way, its instruments measured more than 50 greenhouse gases and black carbon.
The unparalleled altitude- and latitude- specific data collected as part of this program — named HIPPO (for HIAPER Pole-to-Pole Observations) — will soon be made available to researchers generally, notes Wofsy. He expects scientists will mine its data for many years, looking for additional climate trends.
A primary goal of HIPPO was to investigate how well airborne pollutant concentrations match what computer models had predicted should exist. In some cases, as for soot, HIPPO data pointed to serious problems — oversimplifications — in those models. In other instances, such as for oxygen movement in and out of oceans, the new data generally validated computer predictions.
Currently, land plants and the oceans absorb roughly half of all carbon dioxide emitted, notes Britton Stephens, a scientist with the National Center on Atmospheric Research in Boulder, Colo. But details on which parts of which ecosystems do it, under what circumstances and how efficiently remains somewhat of an open book. Simply put: “We don’t understand their behavior at the current time well enough to predict their behavior into the future,” he says.
So airborne observations have been repeatedly compared to what computer models predict. And one example of where the models need fine tuning involves carbon dioxide, HIPPO indicates.
It revealed “large plumes of carbon dioxide over the Arctic,” Stephens reported Sept. 7 at a news briefing. These plumes didn’t come from the Arctic, he says, but bled into Arctic skies from industrial centers throughout the Northern Hemisphere.
“This was a bit of a surprise,” he says, because models had suggested that much of the carbon dioxide should have been sucked up by plants and seas close to where the gas was being emitted. (09/15/11)