A New Approach
To determine the climate impact of particular greenhouse gases, scientists have traditionally relied on surface stations and satellites to measure the concentration of each gas in the air. Then, they have extrapolated such measurements to arrive at a global estimate.
The drawback to that "abundance-based approach," explained Gavin Schmidt, another GISS climate scientist and coauthor of the study, is that it doesn't account for the constant interactions that occur between various atmospheric constituents. Nor is it easy to parse out whether pollutants have human or natural origins.
"You get a much more accurate picture of how human emissions are impacting the climate -- and how policy makers might effectively counteract climate change -- if you look at what's emitted at the surface rather than what ends up in the atmosphere," said Shindell, who used this "emissions-based" approach as the groundwork for this modeling project.
However, the abundance-based approach serves as the foundation of key international climate treaties, such as the Kyoto Protocol or the carbon dioxide cap-and-trade plans being discussed among policymakers. Such treaties underestimate the contributions of methane and carbon monoxide to global warming, Shindell said.
Unpacking the Implications
According to Shindell, the new findings underscore the importance of devising multi-pronged strategies to address climate change rather than focusing exclusively on carbon dioxide. "Our calculations suggest that all the non-carbon dioxide greenhouse gases together have a net impact that rivals the warming caused by carbon dioxide."'/>"/>
|Contact: Sarah DeWitt|
NASA/Goddard Space Flight Center