Well, I warned you. Prepare to be mocked.

1. I'm guessing you didn't check the information in those videos against any external source. If you had, you'd have found out that the object supposedly found by IRAS was later determined to be nothing to do with our Solar System.

2. An object of 4 to 8 Earth masses can't possibly be a Brown Dwarf. That's way too small. I'll let you do the research to determine the mass of such an object compared to the mass of Jupiter. Remember, Jupiter is too small to be a Brown Dwarf, so anything smaller than it also can't be.

3. Planet X can in no way be responsible for global warming on Earth. If it's as far away as the outer planets at the moment, and it's a lot cooler than the Sun, then it's too far away to heat the Earth. Anyway, if it was, there'd be evidence of heating on all the other planets, and there isn't any such evidence. Global warming here on Earth is caused by human actions, by natural processes of the Earth, or a combination.

Conclusion: You can safely ignore the content of the video, even if the narrator once had something to do with science on CNN.