Understanding and updating beliefs on deeply engrained topics can take enormous efforts, but sometimes it can be so hard that the listener cannot even in principle accept the new reality. The listener is simply not ready, he lacks a vast background of reasoning leading to the new understanding.
What fact that you know is true but most people aren't ready to accept it?
By "you know is true" I really mean "you are very confident to be true".
Feel free to use a dummy account.
Ocean acidification is generally seen as one of the problems of climate change. While it might not be a problem in some bodies of water that otherwise would have little carbon, it's a problem in the major oceans.
It's a factor that's fully accounted for in the climate models.