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As nations haggle over CO2 cuts, measurement is tough
(Agencies)
Updated: 2009-11-09 15:36 "It seemed to me for a long time that there's been a huge disconnect between the types of emissions trading and associated verification that might be necessary, that's being considered, and what we can actually measure," said Britton Stephens of the National Center for Atmospheric Research in Boulder. "People have wondered where the CO2 that we're emitting is going and we've been able to tell that in rough numbers that half is staying in the atmosphere. Of the half that is leaving the atmosphere, half of that is going to the terrestrial land plants and the other half is ending up in the oceans," he said. And that is where the real puzzle begins. Because CO2 is shifted around by the atmosphere, scientists need powerful computers to simulate the movement of air around the globe and to crunch all the data from an army of CO2 monitoring sites on the ground, in the air, and in space.
Computer models, though, were years away from proving accurate. "As everyone knows from complaining about weather forecasts, the atmospheric models are far from perfect," Stephens said. Current carbon measurement techniques are complex and time-consuming, although a new generation of measuring equipment using lasers promises much faster and more accurate results and could form the backbone of a greatly enhanced global system. Scientists also need to disentangle natural CO2 from fossil fuel emissions. Fossil fuels, being buried underground for millions of years, are free of very rare carbon-14 isotopes so it is relatively easy to track emissions from burning oil and coal in the atmosphere by analysing air samples. New instruments are also set to make this even easier. Better and more accurate satellite-based measurements are another key part of the puzzle. At present, only Japan's GOSAT measures CO2 from space, giving data on the gas's concentrations in a narrow column of air. But the readings can't accurately reveal the CO2 concentration at the surface where the gas is produced and partially absorbed, nor how the winds are shifting it around. "I think satellites have a chance of being extremely useful only if we have quite an extensive system of both ground based and in-situ measurements through the atmosphere," said Tans of NOAA. Remote sensing of forests via satellites was also crucial, said Canadell. Calculating exactly how much CO2 and other greenhouse gases, such as methane, are released when forests burn or are cleared is critical but this, too, remains an imprecise science. For example, a study published this month in Nature Geoscience says deforestation is responsible for 12 percent of mankind's total greenhouse gas emissions, instead of previous UN estimates of about 17 percent. But the authors note the figure will vary from year to year. "We don't have a system yet which we're reporting annually exactly what's happening with deforestation and degradation. Second, we have little information on these forests of how much carbon there is. What's the biomass of these forests?" Canadell said a future monitoring system would need to marry supercomputers and many different monitoring tools. "What we are going to see is a multiplicity of approaches." Trust was a key driver for investment in the network. "It's not just giving money away making sure people are doing the right thing," he said referring to steps to cut emissions. "It's just we're committing a lot domestically and I want to make sure the rest of the folks are doing the same. Otherwise, I'm putting myself at a disadvantage."
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