Standard conservative responses:

--The globe is not getting warmer

--We don't know if the globe is getting warmer or not

--We do know the globe is getting warmer, but we don't know why

--We do know the globe is getting warmer, but it has a different cause than human activities

--We do know the globe is getting warmer, and it is in part due to human activities, but any action to counter this would be more harmful than letting it get warmer.

--We do know the globe is getting warmer and action needs to be taken, but it should all be voluntary actions by private enterprises, and no new governmental regulations.

And let us not forget: increased atmospheric co2 is beneficial because it increases agricultural production.

Have I missed any?