Summary
Deep inside every drop of water lie tiny signatures from rare forms of hydrogen and oxygen, known as isotopes. These isotopes contain different numbers of neutrons and act like nature’s recorder, revealing where water vapor came from and how it traveled across the globe and formed precipitation. Sensitive to both temperature and humidity along their pathways, these isotopes are stored in natural archives such as ice cores, lake beds, and cave formations. Scientists can read them like time capsules, unlocking stories of Earth’s past climate: how hot it was, how much it rained, and how climate p
