There is no "belief" in science, given that science is a methodological way of gathering evidence about the physical world. To claim that one does not "believe" in observational data is like claiming that one does not " believe" that the sky often appears to be blue. No one can " believe" facts into or out of existence.
OTOH, anthropogenic global warming does not have solid evidence to support its major hypothesis. The issue has become co-opted by politicians, who are subverting what should be the impartial nature of science.
Science, a study of the observable, is clear concise and rather limited in scope. However, evolution, anthropogenic climate change etc is not science in that strict sense.
If an experiment is fraught with assumptions of the otherwise unobservable, then it is not science, but a mixture of assumptive belief and observable phenomenon. Not science. You cannot observe what was, only what is.
Example, If we assume that all carbon was of a uniform atomic number at the origin, then we can infer that so much time has passed since origin based on the observable amounts of isotopic carbon in nature compared to decay rates (assuming static rates of decay-see another wrench). However, if we assume that at origin, there were numerous isotopes of carbon, and or that decay rates may not remain constant) then we have no idea how much time has transpired since origin.
The former assumption is what is used in the “science” of time today, the latter is what skeptics of that first assumptive timeline outcome question. Since no observation can be made as to the actual condition of carbon at origin, then the whole of the output is questionable.
The best answer to this question is “we don’t know” what the characteristic of carbon was at origin; unfortunately, that leaves the output of “how much time” has transpired since origin (creation) has passed. For secularists, that poses a problem, for the faithful, it is irrelevant.