From the press package:
The findings confirm that carbon dioxide is the most potent greenhouse “control knob”
This seems like a last ditch effort (in the face of falling public opinion) from Gavin Schmidt et al. to make CO2 more important than water vapor in regulating the temperature of the planet.
Via emailed press package, embargoed until 2PM EST 10/14/2010:
Of all the greenhouse gases in the atmosphere, carbon dioxide exerts the most control on Earth’s climate, researchers report. Although carbon dioxide’s greenhouse effect has been known for more than 100 years, its primary role in climate warming is still not universally acknowledged.
For example, water vapor is a powerful greenhouse gas and is more abundant in the atmosphere than carbon dioxide. But, it condenses and precipitates from the atmosphere and thus plays a different role than carbon dioxide and other, noncondensing greenhouse gases, such as ozone, methane and chlorofluorocarbons. Andrew Lacis and colleagues conducted a set of idealized climate model experiments in which various greenhouse gases were added to or subtracted from the atmosphere, in order to illustrate their roles in controlling the temperature of the air.
The findings confirm that carbon dioxide is the most potent greenhouse “control knob” and that its abundance determines how much water vapor the atmosphere contains. Without carbon dioxide, the Earth would plunge into a frozen state, the researchers report, though they caution that increasing levels of this atmospheric gas are also worrisome. “This makes the reduction and control of atmospheric CO2 a serious and pressing issue, worthy of real-time attention,” they write.
[Seems a bit out of balance though.]
- Fig. 1. Attribution of the contributions of individual atmospheric components to the total terrestrial greenhouse effect, separated into feedback and forcing categories. Horizontal dotted and dashed lines depict the fractional response for single-addition and single-subtraction of individual gases to an empty or full-component reference atmosphere, respectively. Horizontal solid black lines are the scaled averages of the dashedand dotted-line fractional response results. The sum of the fractional responses adds up to the total greenhouse effect. The reference atmosphere is for conditions in 1980.
Article #14: “Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature,” by A.A. Lacis; G.A. Schmidt; D. Rind; R.A. Ruedy at NASA Goddard Institute for Space Studies in New York, NY.
Contact: Andrew A. Lacis at firstname.lastname@example.org (email).
Here’s the paper: lacis101015 (PDF)