Scientific consensus means that the thing has been sufficiently studied and reproduced that the confidence is extremely high. This isn't just about "soft" sciences. This is true even in high energy physics. You gather some data and there's a statistical chance that it was all due to noise in the measurements or coincidence. Other people gather some more data and the chance that the conclusion is incorrect goes down. Lots of people gather more data, and one of them finds a counter example, but then more people gather more data and that counter example fits with the expected error bar. This is the consensus process. It isn't about feelings or opinions or subjective truths. It's about increasing confidence and reducing error to the point where the entire community of researchers is confident the findings are reliable and can be assumed true.
Scientific consensus isn't the same as truth. It's just the best proxy for truth we can have. Scientific consensus about Newton's Laws was wrong - but it was only wrong at then-unmeasurable scales and precision. The consensus was incredibly useful, even though it was slightly wrong, because the conclusions it gave were widely reproducible and produced predictions with very high confidence that other researchers and engineers could rely on.
Scientific consensus about climate change isn't "consensus" because some scientists "convinced" other scientists or because it's too hard to do repeatable experiments. It is consensus because repeated experiments and measurements and analyses have consistently increased the confidence and reduced the noise in the predictions.
Nothing is ever proven true. Things can be proven false. And things can be proven to be more and more and more likely to be true and less and less likely to be false (because we repeatedly fail to prove them false). At some point things are proven to be SO likely to be true that there is consensus that we might as well treat them as true until someone comes up with a paradigm shift (ala Newton -> Einstein).
The quote in this article assumes that there's never an error bar on scientific measurements. There always is.
http://xkcd.com/882/