Scientists track where greenhouse gases come from and where they go over timeAs she squeezed herself into a telephone-booth-size elevator to ascend a 984-foot tower in Colorado's eastern plains, Arlyn Andrews said with a grin, “This makes me want to go rock climbing.” It’s a good thing she loves climbing tall -structures. An atmospheric scientist at the National Oceanic and Atmospheric Administration in Boulder, Colorado, she is one of many carbon sleuths, scientists who track and analyze where greenhouse gases come from and where they go over time. Think of it like personal finances. To plan for a sound future, it helps to create a budget and keep track of how one is spending money. Similarly, atmospheric scientists need to develop a “budget” for greenhouse gases. But the atmosphere delivers no monthly statement on greenhouse gas dynamics, so scientists have to tease out the information from disparate and often contradictory sources. The key task is measuring the sources, or emissions, of these planet-warming gases, and the “sinks”—forests, cropland and oceans that absorb carbon. This budget can then inform intelligent climate-control policy, whether it be managing one forest or shaping national emissions regulations. The quest to track carbon began 50 years ago when an atmospheric scientist, David Keeling, cranked up an analyser and started running the world’s first carbon dioxide-measuring observatory, at Mauna Loa, Hawaii. Now, thanks to an expanding combination of atmospheric and land-based measuring techniques, scientists can quantify more precisely the sources and sinks of CO2. Globally, carbon sinks are being outpaced by rising emissions. But uncertainty remains high. For instance, researchers think about half of the CO2 emitted into the atmosphere gets absorbed by oceans and land, but they do not know precisely where the gases come from and where they end up.A vexing challenge is that surface inventory assessments—based on measuring forests, agricultural fields and smokestack emissions, for instance—generally do not agree with atmospheric measurements. “We’ve got to close the carbon budget to know precisely what’s going where,” said Kevin Gurney, an assistant professor of earth and atmospheric sciences at Purdue University in Indiana. Last April, Gurney started the Vulcan Project. Named -after the Roman god of fire, Vulcan is a massive database and a graphic map that shows hourly changes of CO2 emissions from the burning of fossil fuels in every locale by every source, including vehicles, power plants and factories. Another carbon budget-mapping tool for atmospheric scientists is called CarbonTracker, a data analysis system begun last year by Pieter Tans, a senior scientist at NOAA’s Earth Systems Research Laboratory and his colleagues at NOAA. The online system shows how CO2 ebbs and flows across continents and how that varies year to year. This summer, a continuing study at a tall tower located on corn and soybean fields in West Branch, Iowa, revealed that the crops sucked a surprisingly large amount of CO2 out of the atmosphere during the summer growing season — as much as 55 parts per million out of a background CO2-equivalent level of 380 parts per million. In January, the next frontier of atmospheric CO2 measuring instruments will begin when NASA launches the first carbon-scanning satellite, called the Orbiting Carbon Observatory. Each day, the satellite will orbit Earth 15 times, taking nearly 500,000 measurements of the “fingerprint” that CO2 leaves in the air between the satellite and Earth’s surface._SUSAN MORAN, NYT
