Simple as it might sound, the first step toward weighing a scientific claim is to establish what it is, as well as what it isn’t.
Read or listen carefully. What exactly is the claim? Where does it sit on the spectrum from likely to outlandish? Do the findings confirm or challenge existing beliefs?
Try to read between the lines when you’re assessing the validity of a claim. Ask yourself: What aren’t they saying? A reputable source will acknowledge missing pieces of the puzzle, or areas where more research is needed.
Finally, don’t be tricked into confusing correlation with causation. Correlation is when two things change together: the relationship could be chance, or there could be a third variable causing both changes. Causation, on the other hand, is a direct cause-and-effect relationship between two things.
Suppose you read that high rates of violent crime are associated with increased sales of ice cream. Ice cream sales may be correlated with violent crimes—both might increase with warmer weather—but it would be quite a leap to conclude that ice cream causes crime. Causation requires a greater burden of proof than correlation, mainly because it requires ruling out all other possible causes.
The problem of distinguishing correlation from causation has been at the root of the global warming debate, an ongoing “hot” topic. While no one can argue with the fact that global temperatures are increasing along with greenhouse gas emissions—a clear correlation—it isn't easy to prove causation in such a complex system.