"CO2 (carbon dioxide) isn't the only greenhouse gas that human are adding to the atmosphere, although it is the most abundant. CO2 equivalent represents the amount of CO2 that would have the same impact on the "radiative forcing" of the atmosphere (i.e. amount of heat absorbed by the greenhouse gases in question) as the combination of gases that we're talking about."

So "C02 equivalent" refers to only greenhouse gases that human activity has emitted?

So, water vapor's greenhouse affect is not included.

Perhaps, a better stab at this would be that "CO2 equivalent" refers to group greenhouse gases which are a concern because it's a group of gases which are considered to be something which are more controllable because their emission could prevented if certain human activities are changed so that the result is the emission can be reduced.

I'm still having a problem with my above definition because obviously human activity could result in addition water vapor and therefore would fall into this category. Is "C02 equivalent" just an arbitrary list of greenhouse gases?

Another term which common is "radiative forcing" which also seems to exclude water vapor.

My understanding of theory of CO2 causing "global warming" is with the additive of "radiative forcing" elements or any increase in value of "CO2 equivalent" the warming this produces generates in additional water vapor and the this increase in water vapor is very significant element in the total warming produced. Is this an correct understanding? And perhaps this is the reason for the exclusion from definition?
And if this correct what is the ratio in which the "radiative forcing" causes increase in water vapor, and has any increase of water vapor globally been measured, which thereby would confirm this assumption?