Hey Mad Lunatic (great name) thanks for the response!
From my perspective, the controversy surrounding Climate Change is not the literal observation of the climate changing, but rather the debate about the cause of climate change and the validity of climate change projections. This is similar to how JP uses "controversial fact"-- few would argue the data of our changing climate is fake, but many find it contentious that humans are to blame, or that this trend will continue.
More semantically, I wouldn't actually call Climate Change a fact, but rather an extremely well-supported theory. This isn't because I'm a climate-denier, it's because scientific theories do not become facts, they are supported by facts + observations to explain our world. https://askabiologist.asu.edu/questions/theory-versus-fact
I do agree we live in an age where truth-denying conspiracies, like flat-earthers, could make some literal observations/facts controversial in certain social circles...