Picturing Greenhouse Gases
Most climate scientists think global warming is real and that a lid should be put on greenhouse-gas emissions. Manvendra Dubey, who heads a Los Alamos team at the forefront of monitoring such emissions, certainly thinks so.
“The world must get serious about global warming and develop international treaties to limit greenhouse-gas emissions,” says Dubey. “And we need an international body to verify that all signatories are in compliance with treaties and to warn countries that are out of compliance to change their ways.”
A key element of implementing such an agenda is the ability to sensitively and accurately measure the atmospheric concentrations of greenhouse gases over any spot of interest and to attribute excess concentrations to specific sources. Such a capability does not yet exist, but the Greenhouse Gases Observing Satellite (GOSAT) is a first step to acquiring it.
Launched in January 2009, GOSAT is the first satellite to measure, beneath its orbit, atmospheric concentrations of carbon dioxide (CO2) and methane, two major greenhouse gases. Dubey’s team will ensure that GOSAT’s measurements can be trusted.
Major cities (red boxes) and major power plants (blue boxes) emit high NO2 concentrations 2 to 10 times the background concentration, as shown here in satellite-measured data from the Four Corners area.
Accordingly, Los Alamos National Laboratory and the Japanese Exploration Space Agency, which launched GOSAT, have signed an agreement: Dubey’s team will have access to the satellite’s raw data, and the Japanese agency will aim the satellite’s gas-measuring spectrometer at the Four Corners area, where Arizona, Colorado, New Mexico, and Utah meet. The Four Corners area is home to two large coal-fired power plants. GOSAT will pass over the area every few days, measuring CO2 and methane concentrations from space. (In addition to the CO2 emitted by the power plants, the area’s oil and gas wells could emit measurable amounts of methane.) Simultaneously, Dubey and his team will use an ultrahigh-resolution, suntracking spectrometer on the ground to measure atmospheric gas concentrations every 5 minutes throughout the day. Their ground-based measurements will validate GOSAT’s space-based ones.
The ground-based spectrometer will also be able to measure concentrations of NO and NO2, pollutants that make ozone, another greenhouse gas. The Four Corners plants jointly emit more of those nitrogen compounds and CO2 than any other point source in North America. In addition to validating GOSAT measurements, the ground-based measurements will help clarify how greenhouse gases disperse from major point sources. The results will help the United Nations’ Greenhouse Gas Information System (GHGIS) develop ways to verify the accuracy of nations’ reports of their emissions, reports that will be used to determine baselines for international climate treaties.
Los Alamos conceived the GHGIS initiative. Other national laboratories and government agencies are also participating.
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