Zipperfish Zipperfish:
What effect would that be, precisely?
Different guys have different theories. Lindzen doesn't sound like he has a problem with the greenhouse effect if it's the accepted sensitivity of 1 degree warming per doubling of CO2. It's modelers insistence on exaggerated warming from proposed positive feedbacks he has a problem with.
I can't think of any well known skeptic coming out saying the greenhouse effect doesn't exist, but I bet one or two might exist somewhere.
Spencer sounds like he's on board with the greenhouse effect, but he thinks negative feedbacks from things such as clouds might balance things out.
I think I heard Pielke Sr. has some sort of theory as to how human activity might affect air currents. I didn't get into it, so I don't know if that's positive or negative.
I've heard skeptic scientists talk about how the effect of certain particulates in actual pollution can be either positive or negative in reference to warming. Meaning the effect can be warming or cooling.
There's a lecture from Christie where he talks about how he's done commissioned studies showing how localized weather and possibly climate can be affected by local human activity.
Watt's is into the Urban heat island effect.
Then there's luke warmers like Bjorn Lomberg who have no problem with what for now we'll call the consensus thinking on warming, but he says adaptation over mitigation in response.
That's just off the top of my head, but basically my feeling is there's lots of different angles where they're saying "yeah, human activity influences climate but..."