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Credit: NASA GISS (Phys Org.com) -- Water vapor and clouds are the major contributors to Earth's greenhouse effect, but a new atmosphere-ocean climate modeling study shows that the planet's temperature ultimately depends on the atmospheric level of carbon dioxide.The study, conducted by Andrew Lacis and colleagues at NASA's Goddard Institute for Space Studies (GISS) in New York, examined the nature of Earth's greenhouse effect and clarified the role that greenhouse gases and clouds play in absorbing outgoing infrared radiation.Various atmospheric components differ in their contributions to the greenhouse effect, some through feedbacks and some through forcings.Without carbon dioxide and other non-condensing greenhouse gases, water vapor and clouds would be unable to provide the feedback mechanisms that amplify the greenhouse effect.Notably, the team identified non-condensing greenhouse gases -- such as carbon dioxide, methane, nitrous oxide, ozone, and chlorofluorocarbons -- as providing the core support for the terrestrial greenhouse effect. A companion study led by GISS co-author Gavin Schmidt that has been accepted for publication in the Journal of Geophysical Research shows that carbon dioxide accounts for about 20 percent of the greenhouse effect, water vapor and clouds together account for 75 percent, and minor gases and aerosols make up the remaining five percent.
The climate forcing experiment described in Science was simple in design and concept -- all of the non-condensing greenhouse gases and aerosols were zeroed out, and the global climate model was run forward in time to see what would happen to the greenhouse effect.
More than ten million compounds of carbon are known.
No other element, except for hydrogen, occurs in even a fraction of that number of compounds.
The study ties in to the geologic record in which carbon dioxide levels have oscillated between approximately 180 parts per million during ice ages, and about 280 parts per million during warmer interglacial periods.
To provide perspective to the nearly 1 C (1.8 F) increase in global temperature over the past century, it is estimated that the global mean temperature difference between the extremes of the ice age and interglacial periods is only about 5 C (9 F).
In 1787, four French chemists wrote a book outlining a method for naming chemical substances.