Looks like there's no consensus amongst ordinary folk either. American Voters Losing Faith in Theory of Global Warming:
The poll asked 1,000 likely voters whether global warming was “caused primarily by human activity or by long term planetary trends.” Only 41 percent said it was human activity, while 44 percent said it was long-term planetary trends. Seven percent said it was “some other reason,” and nine percent said they were not sure.Another sign that maybe, just maybe 2008 was the year that man-made global warming was disproved for the majority of us.
This is a significant shift from a poll conducted last April in which 47 percent said human activity caused global warming and only 34 percent said long term planetary trends caused it.