CO2 yield response are too complex to state they would increase yield.  A green house -based experiment is different than an ecosystem.  You are referencing propaganda from the Western Fuels Association. 

 http://www.highbeam.com/doc/1P2-18854911.html

http://www.cspinet.org/integrity/nonprofits/greening_earth_society.html

Any self respecting agronomist would not make blanket ecosystem/climate statements.