Science starts with hypothesis, and only then studies facts. The purpose of the fact study is hypothesis testing.
No global warmer can state the null (first) hypothesis, because there is none.
The emperor has no clothes.
You're correct that the null hypothesis is important, though if someone were able to make predictions which (1) disagreed with common predictions, and (2) were consistently correct, that person's theories may bear closer examination. They should not be accepted at face value, but the person's ability to make such predictions would suggest that his understanding of the phenomena is better than others'. That doesn't mean that his claimed explanation would be accurate. Many people in centuries past have made a fortune by being able to predict eclipses, though in many cases they lied through their teeth about what was actually going on.