Yes, water vapor is the greatest greenhouse gas. However it is a “feedback”; it responds to the warming that is caused by greenhouse gas forcings, such as CO2, CH4, etc.
This is because H2O molecules only have a residency in the atmosphere of a few days, whereas CO2 can be up there for over 100 yrs, and a small portion of it for up to 100,000 yrs. CH4 has a residency of about 10 years, then degrades to CO2 etc.
I read that article you linked to. The author said CO2 is reabsorbed into water solution and seashells:
When you release a slug of new CO2 into the atmosphere, dissolution in the ocean gets rid of about three quarters of it, more or less, depending on how much is released. The rest has to await neutralization by reaction with CaCO3 or igneous rocks on land and in the ocean [2-6].
:bigyikes: Apparently he never heard of vegetation and photosythesis?
I was also disgusted that he mentioned that some carbon dioxide is still in the atmosphere in 100,000 years but he didn’t say how much. No doubt, out of 1,000,000,000,000,000,000,000 molecules in a gram of carbon dioxide there’ll still be 24 or 25 left in a 100,000 years, but that’s nothing to worry about.
A couple of years ago, lots of websites were talking about carbon dioxide absorbing 22 times as much heat as the same weight of water vapor. Wow! That sounds terrible, doesn’t it!

I knew this was impossible and looked through these websites until I found one that referred back to wikipedia. I checked out wikipedia and they gave references to two scientific papers about carbon dioxide absorbing 22 times as much heat. Unfortunately, wikipedia no longer has those references today. The wikipedia articles are maintained by volunteers who can change things.
Anyway, two years ago the references were there and I checked them out, looking up the actual scientific articles themselves. Each scientific article was about how long equal weights of water and carbon dioxide will stay in the atmosphere and how much heat they’ll absorb in that time. I forget exact numbers, but roughly it was like this. Something like 98% of carbon dioxide is reabsorbed and removed from the atmosphere in one hundred years, while the same percent of water vapor is removed in just a few years. This is of the original one pound of water or carbon dioxide, like you had tagged each molecule like you tag wildlife to watch their movements. Naturally, most of either stuff is recycled in a few years while by chance there are always a few of the original molecules still floating around. This is about as useless as any information I can imagine, but you know how it is in academia: “publish or perish”.
Anyways, if we increased atmospheric carbon dioxide ten times tomorrow morning, in a hundred years the level will be back down to what it was yesterday.
Meanwhile,
over a hundred years,
thousands and thousands of times as much “new” water vapor passes through the atmosphere as “new” carbon dioxide,
and at any moment in time there’s two hundred times as much water in the atmosphere as carbon dioxide, not to forget the “infinite” water in the oceans.

Meanwhile,
the temperature will drop thirty degrees tonight as heat absorbed in the daytime radiates back out to space at night.
