It is true that we cannot use science to verify if someone is enlightened or another noble state, but there have been studies that compare meditators to non-meditators and there have been findings of positive results for those who meditate.
For example, A study reported in the Proceedings of the National Academy of Science, in year 2004 showed that meditation not only produces calming effects, but also lasting changes in the brain.
Researchers found that monks who spent many years in Buddhist meditation training show significantly greater brain activity in areas associated with learning and happiness than those who have never practiced meditation. The researchers measured brain activity before, during, and after meditation using electroencephalograms. They compared the monks to a group of people who had no meditation experience. They found striking differences between the two groups in a type of brain activity called gamma wave activity, which is involved in mental processes including attention, working memory, learning, and conscious perception.
The Buddhist monks had a higher level of gamma wave activity before they began meditation, and this difference increased dramatically during meditation. In fact, the researchers said that the extremely high levels of gamma wave activity were the highest ever reported. The monks also had more activity in areas associated with positive emotions, such as happiness.
(Warner, Jennifer. Reviewed by Nazario, Brunilda, M.D., for WebMD. Meditation May Bolster Brain Activity. WebMD, 2004)
The practice itself follows scientific method in many ways, including direct observation and study, analysis.