I think I read somewhere that Al Gore regretted getting so involved in the Climate Change debate because it became politicized. Reading Ezra Klein’s inaugural piece at Vox helps explain how that process works. Basically, half the country didn’t like Al Gore and had opposed him when he ran for president. That half of the population didn’t just distrust Al Gore, their identity was wrapped up in disbelieving pretty much anything he had to say. The more evidence Gore supplied, the less these people were inclined to believe the evidence.
Obviously, there’s a whole disinformation industry out there, but that’s only part of what has happened. It’s a cautionary tale about who you choose to be your spokesman.