Bill Nye doesn't report what the climate scientists say. Bill Nye is a fraud.
There's a litany. I have no opinion on climate change, except my belief that everyone should stop arguing with each other and fucking do something about it, or STFU. I don't know who Carl Sagan is, or Mann(?) and have no agenda here - except that people without a field of study, or a PhD, or demonstrable knowledge and use of the scientific method should not be called scientists.
Bill Nye is not, nor has even been a scientist, a reputable source of anything, or more than an entertainer and actor. This is like assuming Arnold Swartzeneggar is an expert gunsmith because he's seen using so many in movies.