How do you know that? Knowledge is defined by Webster's as...
Knowledge is acquired by an adversarial process. As Walt stated...there is God or there isn't. It is foolish to state that there is no God when no one can possibly demonstrate this. There is climate change [global warming] or there isn't. It is adversely argued that while there may be climate change, it is not caused by people. On the other hand, it can be argued that CFCs, coal, fossil fuel and other pollutants could be doing the atmosphere no benefit at all.
The Warren Commission Report approached the JFK assassination from only one direction. There was no consideration of any conclusion other than Oswald was the sole assassin. It was a blatant choice..extremely obvious and it remains so. Reasonable doubt did not take a back seat in the so called investigation ...it was not even along for the ride. For the authorities to not arrive at the conclusion that it ultimately did [right or wrong] was just simply unacceptable.
You highlight theoretical so best to say what that word actually means which is, from the Oxford English Dictionary
theoretical
adjective
1 Concerned with or involving the theory of a subject or area of study rather than its practical application.
?a theoretical physicist?
?the training is practical rather than theoretical?
1.1 Based on or calculated through theory rather than experience or practice.
?the theoretical value of their work?
Theoretical understanding does not mean a belief. Something being theoretical does not mean it is not based on facts and evidence, its just that the nature of the facts and evidence is different from the case of a practical knowledge.
It is indeed foolish to state there is no God but an atheist doesn't state that - being an atheist means having no belief in God. Not sure what your comments regarding climate change has to do with this. Saying you have no belief in something or see no evidence for something does not mean you have a belief in the non existence of something or that there is evidence for the non existence of something.
Conclusions about climate change should be based on scientific evidence i.e. facts and shouldn't be a matter of belief.
If there is sufficient evidence/facts to support a conclusion then it is no longer a belief, that is true, but the statement 'I know there was a conspiracy to murder President Kennedy and cover up the crime.' is a statement of personal belief not a statement of knowledge. It is not a fact but a belief.