Any scientist at work in the fields of climate and/or climate change knows that there is a consensus view on global warming: in brief: its happening, and we're doing it, and the IPCC reports reflect that. But if you're a septic you need to push the opposite POV: if you're a septic then there is either no consensus, or (even more bizarrely) there is one, in favour of... errr, accounts differ, but definitely in favour of not doing anything that would upset the coal or oil industries.
However, although all the scientists involved know where the consensus is (though some chose to misrepresent it), there isn't really a way to communicate this to Joe Public: how is JP supposed to know?
Which is where a recent publication in Science comes in handy (Science, Vol 306, Issue 5702, 1686 , 3 December 2004 - I'll skip the DOI cos I hate them - death to DOIs!). Even more handily, it appears to be on full release, and if they ever pull it off you can find it on google, here.
The paper says:
The scientific consensus is clearly expressed in the reports of the Intergovernmental Panel on Climate Change... IPCC states unequivocally that the consensus of scientific opinion is that Earth's climate is being affected by human activities: "Human activities ... are modifying the concentration of atmospheric constituents ... that absorb or scatter radiant energy. ... [M]ost of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations"... In recent years, all major scientific bodies in the United States whose members' expertise bears directly on the matter have issued similar statements. The drafting of such reports and statements involves many opportunities for comment, criticism, and revision, and it is not likely that they would diverge greatly from the opinions of the societies' members. Nevertheless, they might downplay legitimate dissenting opinions. That hypothesis was tested by analyzing 928 abstracts, published in refereed scientific journals between 1993 and 2003, and listed in the ISI database with the keywords "climate change"... papers were divided into six categories: explicit endorsement of the consensus position, evaluation of impacts, mitigation proposals, methods, paleoclimate analysis, and rejection of the consensus position. Of all the papers, 75% fell into the first three categories, either explicitly or implicitly accepting the consensus view; 25% dealt with methods or paleoclimate, taking no position on current anthropogenic climate change. Remarkably, none of the papers disagreed with the consensus position.
Sensibly, the paper continues:
Many details about climate interactions are not well understood, and there are ample grounds for continued research to provide a better basis for understanding climate dynamics. The question of what to do about climate change is also still open. But there is a scientific consensus on the reality of anthropogenic climate change. Climate scientists have repeatedly tried to make this clear. It is time for the rest of us to listen.
[January 2018 update: notice that when I wrote this, the author's name - Naomi Oreskes - meant nothing. She somewhat veered off to the Dork Side after this. In retrospect she got very lucky: no-one else had thought to do this rather trivial exercise, and she got there first. By 2008 she was wrong about Nierenberg; by 2017 she was woo over #ExxonKnew.]