A University of
Colorado Boulder-led team has developed a new monitoring system to analyze and
compare emissions from man-made fossil fuels and trace gases in the atmosphere,
a technique that likely could be used to monitor the effectiveness of measures
regulating greenhouse gases.
The research team
looked at atmospheric gas measurements taken every two weeks from aircraft over
a six-year period over the northeast United States to collect samples of
carbon dioxide and other environmentally important gases. Their method allowed
them to separate carbon dioxide derived from fossil fuels from carbon dioxide
being emitted by biological sources like plant respiration, said CU-Boulder
Senior Research Associate Scott Lehman, who led the study with CU-Boulder
Research Associate John Miller.
The separation was made
possible by the fact that carbon dioxide released from the burning of fossil
fuels like coal, oil, and gas has no carbon-14, since the half-life of that
carbon radio isotope is about 5,700 years—far less than the age of fossil
fuels, which are millions of years old. In contrast, carbon dioxide emitted
from biological sources on Earth like plants is relatively rich in carbon-14
and the difference can be pinpointed by atmospheric scientists, said Lehman of
CU’s Institute of
Arctic and Alpine
Research.
The team also measured
concentrations of 22 other atmospheric gases tied to human activities as part
of the study, said Miller of the CU-headquartered Cooperative Institute for
Research in Environmental Sciences. The diverse set of gases impact climate
change, air quality, and the recovery of the ozone layer, but their emissions
are poorly understood. The authors used the ratio between the concentration
level of each gas in the atmosphere and that of fossil fuel-derived carbon
dioxide to estimate the emission rates of the individual gases, said Miller.
In the long run,
measuring carbon-14 in the atmosphere offers the possibility to directly
measure country and state emissions of fossil fuel carbon dioxide, said Miller.
The technique would be an improvement over traditional, “accounting-based”
methods of estimating emission rates of carbon dioxide and other gases, which
generally rely on reports from particular countries or regions regarding the
use of coal, oil, and natural gas, he said.
“While the
accounting-based approach is probably accurate at global scales, the
uncertainties rise for smaller-scale regions,” said Miller, also a scientist at
the National Oceanic and Atmospheric Administration’s Earth System Research
Laboratory in Boulder.
“And as carbon emissions targets become more widespread, there may be a greater
temptation to underreport. But we’ll be able to see through that.”
A paper on the subject
was published in the Journal of
Geophysical Research: Atmospheres.
One surprise in the study
was that the researchers detected continued emissions of methyl chloroform and
several other gases banned from production in the United States. Such observations
emphasize the importance of independent monitoring, since the detection of such
emissions could be overlooked by the widely used accounting-based estimation
techniques, said Montzka.
The atmospheric air
samples were taken every two weeks for six years by aircraft off the coastlines
of Cape May, N.J.,
and Portsmouth, N.H.
Fossil fuel emissions
have driven Earth’s atmospheric carbon from concentrations of about 280 ppm in
the early 1800s to about 390 ppm today, said Miller. The vast majority of
climate scientists believe higher concentrations of the greenhouse gas carbon
dioxide in Earth’s atmosphere are directly leading to rising temperatures on
the planet.
“We think the approach
offered by this study can increase the accuracy of emissions detection and
verification for fossil fuel combustion and a host of other man-made gases,” said
Lehman. He said the approach of using carbon-14 has been supported by the
National Academy of Sciences and could be an invaluable tool for monitoring
greenhouse gases by federal agencies like NOAA.
Unfortunately, NOAA’s
greenhouse gas monitoring program has been cut back by Congress in recent
years, said Lehman. “Even if we lack the will to regulate emissions, the public
has a right to know what is happening to our atmosphere. Sticking our heads in
the sand is not a sound strategy,” he said.
