The Scientific Consensus on Global Warming
The consensus is clear
In 2013, I coauthored a paper (Cook et al., 2013) tracing the evolution of the scientific consensus on global warming in the peer-reviewed scientific literature. My coauthors and I found that, of those papers taking a position, ~97% endorsed the consensus that humans are causing global warming. Our paper built upon, and is in excellent agreement with, previous research documenting the near-unanimity of expert agreement on this issue (Oreskes, 2004; Doran and Zimmerman, 2009; Anderegg et al., 2010).
But not to the public...

More than half of Americans don't understand that there is an overwhelming scientific consensus on global warming. Further, only around 1 in 10 correctly estimates the correct level of expert agreement (at more than 90%; Leiserowitz et al., 2014). While there is unquestionably a partisan divide on the issue, the enormous discrepancy between public perception and the position of scientific experts cannot be explained away by motivated reasoning alone. Even those along the liberal/Democratic end of the American political spectrum significantly underestimate the degree of scientific consensus on this issue.
And that matters

The disconnect between actual scientific agreement and the public's perception of that agreement is not simply of academic interest. Public perception of scientific consensus is in fact tremendously important in terms of both public acceptance of scientific facts as well as willingness to support policy options. This has been demonstrated in several different studies from different social and communications science teams in recent years (e.g. Ding et al., 2011; Lewandosky et al., 2013; McCright et al., 2013; Aklin and Urpelainen, 2014).
And it is something that opponents of climate policy have known for decades.
And it is something that opponents of climate policy have known for decades.