In science, it's easier to disprove a universal hypothesis. You only need to find one counter-example to bust the entire hypothesis. You might hypothesize, “Man-made industrial era carbon emissions are solely responsible for causing global warming.” That is a universal hypothesis because, by identifying a single warming period that occurred prior to industrialization (e.g., the Medieval Warm Period), you can disprove this universal hypothesis.

You might say, “Why not add appropriate hedging language to make it harder to disprove the hypothesis?” A non-universal hypothesis might be: “High carbon levels in the atmosphere may increase global warming.” This wording makes it more difficult to disprove the hypothesis. You can find a period where high carbon levels exist during an Ice Age era (some research suggest this may have been the case), but that does not disprove the hypothesis (since the hypothesis contains the word “may”). In addition, the hypothesis contains no baseline to reference any increase. Failing to see an increase may not disprove the hypothesis because temperatures may have actually been lower if carbon content would have been lower.

This represents a hypothesis that's virtually impossible to disprove. You might think this is an ideal hypothesis, but then you will have exited the realm of science and entered the world of politics. In science, the only purpose of creating a hypothesis is to discover a theory, i.e., a universal truth. To discover a universal truth, you need a universal hypothesis. Any lesser hypothesis has no value in science or truth, telling you a lot about politics.