It has been changing a lot for the past 50 years, globally. Dropping 21% in fact.
http://www.cdc.noaa.gov/cgi-bin/data/timeseries/timeseries1.pl"
Also documented by:
‘http://www.theclimatescam.se/wp-content/uploads/2009/03/paltridgearkingpook.pdf" ’ by Garth Paltridge, Albert Arking...
Yes, but that is only for anthropogenic sources, not all of them. Water vapor is a forcing, as well as a feedback. To exclude the major forcing / warming constituent is not entirely fair in their calculations. It also appears that contrary to popular opinion, water vapor is the largest single...