Science is based on the belief that there is a real world out there that has properties anyone can discover. What made this world "real" was that these properties did not depend on anybody's opinion, so you didn't have to give a damn about anybody else's opinion of your research either; you could discover the truth yourself, and be right even if everybody in the world disagreed with you.
Now we have social science. It's based on the belief that reality is defined by majority opinion. Naturally, one man's opinion is worthless, and only when a consensus is reached can you state that you know anything.
I'm afraid you completely misrepresent both science and what you call social science (but isn't). The problem is not whether the world is real: the problem is how can we know what these properties are.
Truth is not self-evident, as you imply. In fact, science does not produce "truths" at all: it produces theories. Scientists gather evidence and construct theories to explain the evidence. This is inductive reasoning: it can never be 100% certain.
Science isn't something "anyone" can do, as you imply: in many cases it takes a lifetime of expert training to be able to assess scientific evidence - and even then, there are honest disagreements and mistakes. Take your field of expertise. Can anyone make sound judgements? Is the common sense of the amateur dependable? I'll wager not.
So, we have scientists evaluating evidence, but they don't all agree. There is always evidence that doesn't quite fit. A scientific theory is never perfect. (If they did agree, if everything fit, then they would move on to something else because that particular problem would no longer be interesting!) With these scientistific experts disagreeing, how are we to decide who is correct?
Consensus. Communication. Agreement does not make things true in the world, but it is the best method we have for trying to judge whose truth is the right one. And it is imperfect.
You have fallen into two errors: First, of believing that once Truth is found that fact can be known and reliably communicated. Second, of believing that the only alternative is to believe nothing is true and reality is the invention of majority opinion. You are wrong on both counts.
Such misunderstandings lie at the root of anti-evolutionary belief, and sustain conviction that climate change science is a fraud. A non-expert believes he has found the one critical piece of evidence that disproves the consensus, and becomes convinced that this overturns the science. Science isn't calculus. It doesn't work like that.
The debate over evidence and whether it is possible to know Truth is an ancient one, reaching right back to Plato. One of the most important and influential scholarly works of the 20th century (and the source of the term "paradigm shift") is The Structure of Scientific Revolutions by Thomas Kuhn. I highly recommend reading the whole book: every scientist should read it. There is a pretty good recent overview at The Guardian, of all places. (Though the last bit about science being data- rather than theory-driven is bunk. It is both.)
As for social science, fifty years ago it was caught up in the belief that it could discover scientific laws of society akin to Newton's laws of physics. Then in the 1980s and 1990s there was a widespread rejection of this position, which in many cases resulted in an extreme postmodern rejection of science as a special way of acquiring knowledge. Thankfully, both extreme positions have now been widely rejected.