And as far as I'm aware it is already doing that - temperature continues to rise.
But my point is that this is not an "observation" in the same sense that looking at the earth is. There is a problem in that the round earth theory only makes one prediction - that the earth is round. It doesn't even matter why. It's such a simple theory that can either be proven or disproven with one simple observation. If the earth is round, then round earth theory is confirmed. Climate change makes predictions that can be observed, but these observations can be the result of other factors too. Warming over half a century could be the result of solar activity. It could be the result of ever-increasing accuracy in regards to measurement. It could be outright manipulation of figures. There are lots of theories that can predict warming, not all are correct just because warming is happening.

When there is an event of the scale of an island nation being claimed by the ocean, then we know for certain that sea levels are rising. That alone doesn't prove man-made climate change is to blame, but we at least know that we have a very serious problem that needs addressing. At this point, the most viable theory, which is indeed climate change, will determine how we go about tackling the problem.

Perhaps, with all due respect, this discussion of how to evaluate a scientific argument is a good example of why experts in science are better able to judge the merits of a theory than are laypeople.
Yes, but the problem with "leave it to those in the know" is that we have to put our trust not just in the sincerity of those in the know, but also in the entire system that educates them. That leaves the layman vulnerable to manipulation. What happens when you take your car to a garage and they think you haven't got a clue? They create expensive problems that need fixing. Basic economics.