Semmelweis essentially discovered germ theory (or something close to it) but everyone knew he was wrong and as a result it took another 30 years or so before "unpreventable" deaths became preventable. How many people died because folks in charge just knew they were right? https://en.wikipedia.org/wiki/Ignaz_Semmelweis
The point here isn't that climate deniers are somehow right and that history will vindicate them, it's that pretending to know something absolutely often (frequently? nearly always?) makes you a charlatan.
There is no healthy skepticism in denying human participation in climate change. The efficacy of myriad proposed solutions are still out for discovery and debate, but that's where we should be accepting alternative viewpoints, not on whether or not human activity has any causality.
The problem with 'climate change' aka. 'observed warming is attributable to humans therefore we must start recycling, blah, blah, blah' is one it's mostly political, two, the science is not clear in a 'These are our predictions we passed the predictions', eg. it's clear the earth is warming, but it's also clear the computer models don't work, and it's really not clear what will happen if the warming continues, because a) we don't know how warm it will be, and b) we don't know what that warmth will do.
When people say words like consensus instead of hypothesis you can tell they are having a political debate that involves science rather than a scientific debate that involves politics, in the exact same way that the intelligent design people do the same thing.
If I light a piece of paper on fire, I might not be able to predict the exact shape of the flame at any given instance, but I can be pretty damn sure it will end up as ashes.
Only because you don't have to point out that there's a consensus if it's not a political issue. Lots of things have general consensus - we just have absolutely no need to point out that most scientists agree on something unless someone doesn't believe that's the case.
There's a consensus that generally bad things will happen if we let climate change get out of hand. There's not a consensus on precisely what form those bad things will take.
Wiki isn't the best source on this topic, but here is one list, for example: https://en.m.wikipedia.org/wiki/List_of_scientists_opposing_...
The work that has been done relies heavily on models and simulations. These are both not realistic (because there are many factors that are too complex to model, or that we don't yet understand fully) and have not predicted temperature well since the outturn of past years has been significantly lower than predicted by the envelope of such models.
The political climate clearly is not one where people feel free to speak (see other stories on attempts or proposals to criminalise the expression of dissident views under certain circumstances or to create legal liabilities) and in that situation many people will keep quiet and hide what they really believe. See Timur Kuran's work on preference falsification.