Getting a Vertical View of Greenhouse Gas Emissions

By Leland Rucker

BOULDER, Colorado, June 2, 2003 (ENS) - Policymakers, governments, and citizens deserve accurate climate information on which to base decisions about temperature changes around the planet, and researchers from the National Oceanic and Atmospheric Administration believe their new airborne experiment will fill a current gap in climate modeling and monitoring of greenhouse gases.

Scientists and researchers aboard a specially modified University of North Dakota aircraft will be measuring the vertical journey of greenhouse gases, especially carbon dioxide and sulfur hexafluoride, as they rise from the Earth's surface into the upper atmosphere.

These "vertical profiles" from the CO2 Budget and Regional Airborne Study - North America 2003 can be plugged into climate modeling software to better gauge future temperature changes, says principal investigator James Elkins, a researcher at the National Oceanic and Atmospheric Administration (NOAA) Climate Monitoring and Diagnostics Laboratory in Boulder.

Carbon dioxide (CO2), emitted by the combustion of fossil fuels such as coal, oil and gasoline, is the most abundant greenhouse gas, which blankets the Earth, trapping the heat of the Sun's rays close to the planet's surface.


University of North Dakota Cessna Citation II, a modified executive jet for atmospheric research (Photo courtesy Federation of American Scientists)
Sulfur hexafluoride (SF6) is an inert gas with excellent cooling, insulating, and arc quenching capabilities used in electrical breakers, magnesium casting, sound insulation, semiconductor etching, and chemical lasers. It is also a potent greenhouse gas with a very long resident time in the atmosphere.

The NOAA study could have international implications as nations begin attempting to meet standards created by the Kyoto Protocol. This international treaty under the UN Framework Convention on Climate Change requires 37 industrialized countries to reduce their emission of six greenhouse gases an average of 5.2 percent of 1990 emissions during the five year period 2008-2012.

Under the administration of President George W. Bush, the United States has backed out of the Kyoto Protocol originally signed under President Bill Clinton. With about five percent of the world's population, the United States emits some 25 percent of the world's greenhouse gases.

Better information is critical to making informed decisions about how to deal with the warming of the planet. "People could argue that since we can't get a current vertical profile, how are we going to do this in the future," Elkins says. "Climate models should be more accurate."

Learning how carbon dioxide is transported into the atmosphere is the key to better understanding the current warming trend. "So the name of the game is understanding how these chemicals are transported into the atmosphere," Elkins says. "These chemicals will cause global warming. So you have to know how it works. There are so little data on the vertical profiles."

Data show that concentrations of CO2 in the atmosphere over the last 40 years have increased, says Harvard professor and lead researcher Steven Wofsy, but we do not know exactly how or why that happens. "It's not increasing as fast as it should if all we put out stays in the atmosphere," he says. "Some of it is going somewhere, but not the atmosphere."


Harvard professor of atmospheric and environmental science Steven Wofsy (Photo courtesy Los Alamos National Lab)
That is what Wofsy calls the miracle. Some CO2 goes into the ocean, and more is stored in plants. "Nobody programmed this, and nobody is paying to dispose of it. It's one of those miracles you want to look closely at, because we didn't get a guarantee that this will continue, and maybe all this could come back later," Wofsy says. "It gives us a reason to try and understand where it's going and why it's going there."

That is important from a policy standpoint, Wofsy notes, because we need to know how it happens and how it might change in the future. "Kyoto was trying to reduce U.S. emissions by seven percent, but the land is doing 25 percent on its own," he says.

The study is designed to make detailed observations in the atmosphere and allow scientists to determine large scale greenhouse gas sources and sinks.

Test flights began May 23 from Jefferson County Airport in Broomfield, Colorado, just south of Boulder, and will continue through June 23.

The Cessna flies a "racetrack" pattern 30,000 feet above sea level that takes it west over recording stations in California and Oregon, and across Canada to the U.S. east coast, where it will dip into the pollution plume of the New York/Washington, DC corridor before returning west across the middle of the country to Boulder.

The track being studied goes around an area scientists call a carbon sink, a place where greenhouse gases are stored in plants and vegetation.


Gas measuring instruments aboard the aircraft (Photo courtesy NOAA)
Other flights from an airfield in Pease, New Hampshire, and over the Pacific Ocean from Eureka, California, will examine the mix of ocean and land air masses.

The Cessna is able to fly lower than most jets, which allows better measurements at different altitudes. Its data will be combined with simultaneous ground measurements and from smaller aircraft in airspace below the Cessna's reach to give researchers a complete look at gases' entire journey from emission to dissipation.

"We need those ground stations because they provide boundary conditions," says Elkins. "We can only fly four hours at a time."

The cooperation of a host of agencies, universities and research groups has been required to allow this research to take place.

Wofsy says that if the study is successful, it will be critical to start gathering data with greater frequency than just two flyovers of the area in a month. "We will need to make measurements very routinely and accurately. We need a systematic approach to the measurement," he says. "If you're taking samples here and there, you don't know what to make of it."