From 1976 till '89 I worked as an analytical chemist in the coal industry. I analysed atmospheric air nearly every working day. During that time I saw atmospheric carbon dioxide go from 0.0320% to 0.0345%. That is a very large increase and was not hypothetical or guesswork. My measurements were confirmed by the Baseline Monitoring Station at Cape Grim, Tasmania.
Absorption of infra-red radiation by carbon dioxide increases with increases in concentration, a fact known for more than 100 years.
The only way increases in carbon dioxide could not contribute to extra warming of the atmosphere is if the atmosphere as a whole was already absorbing all the infra red radiation. This is not so, and the extra heat load can be calculated from fairly simple equations known to first or second year chemistry and physics students.
Since a warmed atmosphere will itself radiate more heat back into space, extra cloud cover caused by more evaporation from oceans will reflect more radiation back into space and there are other factors going on, the actual amount of warming over say ten years is not certain and this is where computer modelling comes in.
Incidentally, a TV documentary screened 2 or 3 years ago claiming that the Earth had been cooling since 1998 was exposed as a fraud about six months later. Global measurements were produced showing that the warming 1998 - 2006 was consistent with 0.1 centigrade per decade, not a decrease as the makers claimed. This was despite a slight decrease in the the output from the Sun consistent with the normal 11 - 12 year solar cycle.
You should have seen the documentary maker squirm. The fraudulent documentary was financed by American business interests and deliberately left out valid data. These people have been lying about this for at least 15 years and have made it a party political issue in the USA at least.
I am quite aware that water vapour and methane are greenhouse gases. The methane content of the atmosphere is low and began to decrease when western finance of petroleum installation in the old Soviet Union led to repairs to leaks. Another factor here is use of coal seam gas and even garbage dump gas, both mostly methane, as energy sources, something that was only a proposal 30 years ago.
Water vapour is entirely outside human control. Carbon doxide is partially under human control. You only work on the things you can affect.
EDIT - How is it that you accept political arguments which are always dodgy, whatever political side they come from, and ignore plain facts which contain about as much high - falutin' science as the proposition that the ocean contains salt?
