The role of greenhouse gases is to cool the atmosphere through radiating energy to space. The dominant gases in the atmosphere such as nitrogen and oxygen cannot do this. The next most dominant gas, water vapour, can. In fact, water is the main greenhouse gas and more than 98% of the effect of atmospheric greenhouse gases is due to water vapour. The next most dominant gas, argon, cannot. The traces of CO2 and methane can.
If there were no water on Earth, then there would have been a runaway greenhouse billions of years ago. But in fact there is a lot of water on Earth.
Very little of the effect of CO2 is due to human activity. If humans burned all the fossil fuels on Earth, the atmospheric CO2 content would not even double. So, why are we focusing the discussion about sustainable development on this one element out of the 92 natural elements in the periodic table? What’s so sexy about CO2?
(Source, Heaven and Earth, Ian Plimer)