Here's how I determine if I'm listening to an fossil fuel industry paid liar. First look at his/her background. Is he/she a climate scientist or experienced in a related discipline? If not, forget it, stop listening. Second, does he/she spend a lot of time trying to discredit particular climate scientists, organizations, studies, or activists. This is a judgement call, but if the answer is yes, it's a red flag. Third, does he/she discuss the mountain of empirical evidence that supports the assessment that climate change is an existential threat to all life on Earth. If not, he/she either doesn't know the subject or is deliberately trying to hide or distort the facts.