By my definition, 24 of the 13,950 articles, 0.17% or 1 in 581, clearly reject global warming or endorse a cause other than CO2 emissions for observed warming. The list of articles that reject global warming is here. The 24 articles have been cited a total of 113 times over the nearly 21-year period, for an average of close to 5 citations each. That compares to an average of about 19 citations for articles answering to "global warming," for example. Four of the rejecting articles have never been cited; four have citations in the double-digits. The most-cited has 17.The study period ran from 1991 to this year.
The date of the start of this study is notable. I'm not a climate scientist, but from what I understand the 1980s saw the key pieces of information that settled the debate. In addition to the 1980s being the start of the current extremely rapid temperature rise, satellite temperature measurements supported warming models better than the alternatives. So if you were to run a similar analysis for earlier years, you might well find a different result.
Of course, you might wonder how a twenty year-old scientific consensus has not percolated into the public consciousness. But this is not the first time that something like this has happened. A similar phenomenon happened with the smoking-cancer link. The earliest suspicions about this connection actually date back to the 1920s, but it was not till the 1950s that the scientific evidence really came in. And the tobacco industry responded to this by engaging in a concerted effort to obscure that simple fact. This is not controversial, either; it was the basis for the major payouts from cigarette companies in class action lawsuits. But the extent of this campaign can be seen that as recently as 1994, Rush Limbaugh could deny that smoking cause cancer; and less than two years ago, claim that second hand smoke is harmless.
I'm certainly not the first to draw this parallel, but I think it's an analogy worth repeating. The tobacco companies were willing to try and suppress scientific evidence to make a few more millions, and as a result thousands of people died. But even among smokers, only a fraction were affected, and more people suffered from smoking themselves than from second hand smoke. In contrast, the consequences of global climate change will hit everyone, and many people will suffer who were not responsible (because they aren't even born yet).
But, hey, a few rich people will get richer, so it's all for the best, right?