The best example of this I know is global warming, and it's relationship to carbon dioxide and other "greenhouse" gasses. The overall facts are not disputed by scientists and anyone who has studied the issue. Global temperatures have been rising for the last 120-130 years or so, and carbon dioxide has been steadily rising during the same period. Now, correlation doesn't prove cause and effect, so is it just coincidence? That carbon dioxide is a well known greenhouse gas suggests at least some cause -- this is the basic position of the "97% consensus", though I don't know if it has been proven or is just an informed hypothesis. It is certainly reasonable.
Here is a chart that supports this conclusion:
The thick black line was added by me. Why not just do a linear correlation and fit a straight line through the points? One could fit a very nice line, with a correlation coefficient well above 0.9; but this fit is clearly better. The situation with carbon dioxide concentrations is even better:
One could fit an even much better line through this data set; the yearly average line virtually is straight! More, there are serious reasons to assume, if nothing drastic is not done, it will even start to become exponentially increasing in the near future.
Put the evidence of the two graphs together naively and the conclusion is stark: over the rest of the 21st and into the 22nd centuries the globe is going to keep getting warming, even warming exponentially, until at some point the results will be calamitous for human beings and many other species as well. Again, if nothing serious is done, starting now or soon, to abate the situation.
But notice the leveling out or even cooling, starting about 2005. A blip, or the beginning of another cooling episode, like that of 1940-1975. What does it mean? I suggest we simply have insufficient data to tell yet. And there is serious debate, with most climate scientists/organization insisting the world is still warming. But look at this:
Keep hunting.
