Almost 200 years after the greenhouse effect was discovered, and 150 years after its experimental proof, NASA scientists have finally demonstrated that CO2 is the most important greenhouse gas. That’s despite the fact that it only accounts for around one-fifth of the Earth’s greenhouse effect, whereas water vapour accounts for about half, and clouds – water in its solid or liquid forms – contribute a quarter.
“It often is stated that water vapour is the chief greenhouse gas (GHG) in the atmosphere,” write NASA’s Andrew Lacis, Gavin Schmidt, David Rind and Reto Ruedy in top journal Science on Thursday. “This would imply that changes in atmospheric CO2 are not important influences on the natural greenhouse capacity of Earth, and that the continuing increase in CO2 due to human activity is therefore not relevant to climate change. This misunderstanding is resolved through simple examination of the terrestrial greenhouse.”