Scientists say they have found a way to measure changes in the levels of carbon dioxide in the atmosphere, a method which they claim could be used to ensure countries did not exceed their CO2 emissions limits.
Scientists from the University of Utah and Harvard used measurements from three CO2 monitoring stations in the Salt Lake Valley to detect variations in emissions of 15 percent or more.
The research was carried out by Jim Ehleringer, a distinguished professor of biology at the University of Utah. Ehleringer has been monitoring CO2 emissions at six sites in the Salt Lake Valley since 2002 as part of a National Science Foundation-funded study of the urban air shed.
For the new study they created a computer simulation using measurements from three of the sites – the University of Utah, downtown Salt Lake City and Murray, Utah. They combined this with data from weather stations and with satellite data showing the urban and rural mix of landscapes in the valley.
The measurements were less precise than the 5 percent accuracy recommended by a National Academy of Sciences panel and the study’s authors acknowledged satellite monitoring might in the end prove more accurate than their ground-based method. They said ground-based measuring was also hampered by fluctuations in CO2 due to the effect of photosynthesis from plants, which the researchers said was hard to factor into the results.
“The idea is can you combine concentration information – CO2 in the air near the ground – and weather patterns, which is wind blowing, and mathematically determine emissions based on that information,” Ehleringer said in a statement.
According to the professor, the computer model predicted higher emission levels than a federal government survey, which based its results on interviews with gas- and coal-burning utilities and fuel and natural gas sellers. “That shouldn’t surprise you,” Ehleringer added. ”People are underreporting.”
Many countries around the world have already imposed limits on their CO2 emissions.
Under the Kyoto Protocol, signed in 1997 and entered into force in 2005, 191 countries around the world have agreed to collectively reduce their greenhouse gas emissions by 5.2 percent on average for the period 2008-2012. Of the original signatories only the U.S. has refused to ratify the terms of the protocol.
According to Ehleringer and his team, there have been several earlier studies aimed at measuring CO2 levels in cities, but none anywhere near accurate enough for verification of international treaties. The only one that has so far provided enough precision — a study of emission levels over the German city of Heidelberg — proved too expensive for routine use.
Ehleringer carried out the study alongside four Massachusetts atmospheric scientists: Kathryn McKain and Steven Wofsy of Harvard University and Thomas Nehrkorn and Janusz Eluszkiewicz of Atmospheric and Environmental Research.
Their results were published this month in the online edition of the Proceedings of the National Academy of Sciences.