We know that water vapour and clouds are major contributors to Earth’s greenhouse effect, providing the feedback mechanisms to power the warming that keeps us from another ice age. A new study, however, has shown that it is carbon dioxide –- which only accounts for 20 percent of the greenhouse effect, compared to water vapour and clouds accumulated 75 percent –- that regulates the planet’s temperature.
The study, to be published in the Friday edition of the journal Science, shows that without the non-condensing greenhouse gases –- carbon dioxide, methane, nitrous oxide, ozone and chlorofluorocarbons –- water vapour and clouds would be unable to maintain the planet’s temperature on their own, and we would collapse back into another ice age.
“Our climate modeling simulation should be viewed as an experiment in atmospheric physics, illustrating a cause and effect problem which allowed us to gain a better understanding of the working mechanics of Earth’s greenhouse effect, and enabled us to demonstrate the direct relationship that exists between rising atmospheric carbon dioxide and rising global temperature,” said Andrew Lacis, from NASA’s Goddard Institute for Space Studies (GISS) in New York.
New Climate Study on CO2 and Other Greenhouse Gases
The new atmosphere-ocean climate modelling study was simple in its form; simply removing the non-condensing greenhouse gases and aerosols and letting the climate model proceed and seeing what would happen.
As it turns out, without the support provided by the non-condensing greenhouses gases, Earth’s greenhouse effect -– which keeps our planet warm –- collapsed and Earth entered a new icebound state.
“When carbon dioxide increases, more water vapor returns to the atmosphere. This is what helped to melt the glaciers that once covered New York City,” said co-author David Rind, of NASA’s Goddard Institute for Space Studies. “Today we are in uncharted territory as carbon dioxide approaches 390 parts per million in what has been referred to as the ‘superinterglacial.'”
“The bottom line is that atmospheric carbon dioxide acts as a thermostat in regulating the temperature of Earth,” Lacis said. “The Intergovernmental Panel on Climate Change has fully documented the fact that industrial activity is responsible for the rapidly increasing levels of atmospheric carbon dioxide and other greenhouse gases. It is not surprising then that global warming can be linked directly to the observed increase in atmospheric carbon dioxide and to human industrial activity in general.”
Source: NASA GISS
Image Source: davedehetre