3) 'Consensus science' is simply an expression of the collective politically correct thinking. It only takes one scientist employing the actual scientific method to uncover the facts of the observable cosmos. Examples of consensus science of the past include such things as the earth as the center of the universe, flat earth, spontaneous generation, the theory of humors, etc. The high priests of the age tout consensus science. The true scientist stands on the solid foundation of data observed, the inferences that can properly be drawn from it and the repeatability of the findings.
You also have to be very wary of arguments like this. One problem is that it is very easily abused. In a sense, all science proceeds "by consensus". So how do you discern between "real science" and "consensus science"?
You gave some pretty darn good examples. Things like the geocentric theory of the universe, spontaneous generations, and humors illustrate the growth of science. Those things actually made sense, given the context of understanding at the time. But it is a fallacious argument to say that, just because we once believed something that we now know is incorrect, that ALL SCIENCE is incorrect. Attempting to use this argument to disprove GW is like saying that we once treated most illnesses by sticking leeches on people, so therefore all our current medecine is invalid. It is an error in logic.
You can also get into other problems, such as talking about the "flat earth". True, once upon a time, the "flat earth" theory was common. But since at least the time of the Ancient Greeks, that has not been true. Contrary to the popular story many of us heard in grade school, Columbus and crew KNEW the Earth was round, and had absolutely no fear of "falling off the edge". The fear was that many scientists of the time said that Columbus was using bad estimates of the size of the Earth, and there was no way that his crews would last until they reached the Orient. And as it turns out, the prevailing science of the time was right. Columbus just got lucky that there was an "unknown" continent in between Europe and Japan, which allowed his crew to survive.
You talk about a "solid foundation of data observed", but when it comes to Global Warming, we HAVE that. We have tons and tons of observed data, and all our observations point to Global Warming. Countless scientists in hundreds of different branches of science have all explored their own paths, and ended up at the same conclusion. Trying to say that all of these thousands and thousands of scientists over all disciplines of science and decades of work are all suffering from a mass delusion, or are all part of some consipiracy, is simply ridiculous. An awful lot of those scientists wanted to disprove GW, but their efforts have done nothing but help confirm it.
At this point, there is no doubt whatsoever that GW is happening. The unknowns are how fast and how much things will warm up before other factors kick in to help get the Earth back to a steady state, what precisely the impact of that warming will be, and whether or not the Earth will be a good habitat for humans (or even if humans will still be around) once it finally achieves the next steady state.
There is also no doubt that the Earth will survive, and will not be destroyed by our emissions. The doubt is about whether we can start living in a sustainable fashion before we drive ourselves into extinction, or at the very least, before we destroy our current civilization and send ourselves back into another Dark Age.