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Vulcan Logic and the Missing Sink

Researchers studying a mashup of existing data are tracking exactly where carbon is entering — and exiting — the atmosphere.

The daily carbon dioxide emissions report probably doesn't come up very often at America's dining room tables, but Kevin Gurney and researchers from the Vulcan Project hope to soon see that change.

Gurney leads Purdue University's Vulcan Project, which has produced the nation's first county-by-county, hour-by-hour snapshot of CO2 emissions. With Vulcan — named after the Roman god of fire and funded by the federal government through the North American Carbon Program — it is possible to peer, literally, into your own backyard (or your neighbor's) to see how your local area is contributing to the global problem that ultimately leads to global warming.

A little goes a long way
The gases nitrogen and oxygen account for 98 percent of the Earth's atmosphere. As one of the alphabet soup of trace gases naturally present in the air, CO2 accounts for a mere .038 percent of the atmosphere by mass; however, it has a disproportionate impact on warming.

As Gurney, the associate director of the Climate Change Research Center at Purdue University, explained, "It comes down to how we look at the atmosphere. If we look at it in terms of mass — just the weight of things — then CO2 is very small, but if we think about it in terms of the amount of infrared radiation it would trap, then CO2 would look huge."

Although the oceans remove one-third to one-half of the carbon dioxide produced each year, "the bad news is, their ability to do so appears to be diminishing," Gurney said. Meanwhile, the thousand-year atmospheric lifespan of CO2 means levels will continue to ratchet up even if emissions ended immediately.

Nevertheless, given what is known about carbon dioxide sources and sinks (locales or processes that remove CO2 from the atmosphere), scientists say CO2 has not accumulated as fast as one might expect, leading to the ironic question, "Why is the atmosphere not more polluted?"

Gurney and Daniel Mendoza, a graduate student with the Vulcan Project, suspect the answer may lie in an unrecognized carbon sink somewhere on the planet, and in light of the diminishing CO2 capacity of the seas, they believe this "missing sink" will play an important role in the carbon policy equation.

Though Gurney said CO2 concentration varies by no more than a few parts per million from pole to pole, he believes that mapping these barely perceptible peaks and valleys in CO2 levels could lead the way to the missing carbon sinks.

"In effect the weather map is a great analogy," he said. "Most people know that the air has temperature everywhere, but we know that in some places it's a bit higher and in some places it's a bit lower just like a weather map shows. CO2 is kind of like that. It's everywhere but it definitely has little bumps and valleys depending upon what's happening at the surface.

"The absence of the gas, where it would otherwise be expected, would indicate the possible location of the missing sinks."

To find the hidden sink, Gurney explained, research must first pin down where the observed carbon dioxide in the atmosphere originates. But that is not easy. CO2 mixes thoroughly with air as it travels over the planet. "You can find CO2 at the South Pole that was generated by industrial activity in the Northern Hemisphere."

Nonetheless, Gurney said, "We've known at the national level how much is coming from the U.S. as a whole," but prior to the Vulcan Project, the best estimates of emissions at the state level were based on fuel sales figures and shipping records.

Drilling down to the local level the math gets even fuzzier. Gurney says "the gold standard" of CO2 emissions estimates merely apportioned total discharges among jurisdictions on the basis of population density. Noting the obvious flaw in that approach, he points out that major CO2 emitters such as interstate highways and power plants, which alone account for 40 percent of U.S. emissions, are often a considerable distance from the population centers they serve.

To get a more accurate view of emissions sources Gurney turned to the U.S. Environmental Protection Agency and its network of local air pollution monitors. "Emission monitoring has gone on for 40 years — since the 1960s — which is an amazing legacy of information and infrastructure built and perfected over four decades," he explained. "In fact it is so good that we almost take it for granted now."

Reverse engineering
Although the EPA monitoring system was never intended to record CO2 levels, Gurney said their reports can be reverse-engineered to quantify the CO2 component of the exhaust that produced the pollution, "provided you know the type of device and fuel."

Mendoza is using data recycled from transportation studies picked up by "the thin wires that you can see that run across the road."

"They're the Federal Highway Administration's weight and motion sensors," he said. "They classify vehicles as either light duty or heavier duty" as they pass over the counter. Mendoza says from this and similar data, Vulcan can generate CO2 emissions figures along major roads.

Although Vulcan collects no original field data, Mendoza says an incredible amount of detail can be coaxed from archival sources. Looking back to the year 2002, he says, Vulcan provides a sector-by-sector breakdown of CO2 emissions from the power plant sector, residential, commercial sectors, and the cement sector. "We can bring it down to a 10-kilometer-by-10-kilometer grid and provide a temporal pattern for most sectors," he said.

"We were a little bit floored by how much emissions actually come out of very unpopulated areas — a lot of that is due to electricity generation, which is such a great part of the economy here," Mendoza noted.

He said Vulcan delivered an additional surprise, revealing large cities to be "much more" CO2 efficient than smaller communities. Aside from the efficiency of urban mass transit, Mendoza believes lifestyle plays a role in the disparity. "Here in rural Indiana, we have large houses out in the middle of two acres, so the heating cost are much larger, but in the city you have the urban heat island effect keeping costs down."

The Vulcan Project Web page offers animated displays that show local CO2 emissions ramping up and down in response to heating and cooling needs, traffic patterns or other cycles of daily American life for the year 2002.

International Appeal
Gurney said U.S. government officials asked him if Vulcan can be used for "verification purposes" for an eventual climate treaty. It's an idea he finds appealing: "It would certainly be better to have an independent scientific body perform that function than a government."

He believes the average citizen can benefit from a dialogue with Vulcan as well. (You can take a look immediately using Google Earth.)

"I was pretty amazed at how interested people were when we released the maps and the movies," he said. "It's always been difficult to communicate the essence of this problem because it's very abstract in a certain way. One of the things that Vulcan has done is start to make this problem a bit more real and at least make it recognizable to people's lives.

"It brings the discussion down to the human scale, to the scale people live, in their state, their county, in some cases, their city. It brings it into their living rooms."

Mendoza said his next tasks will include adding data from Mexico and Canada so the Vulcan grid covers the entire continent.

Gurney, who predicts Vulcan eventually will produce emissions forecasts three months in advance, said he has received funding for a global version of the project and is currently exploring partnership opportunities with candidates in Europe, Asia and South America.

Despite the detour down the public awareness road, Gurney says he has not wavered from his initial quest to discover the missing sink. However, with a better grasp on where the CO2 originates, he says it will take direct observation, on a global scale, to determine where it might be going, and that job he said, is best performed from space.

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