evidence: Thermometers, ice cores, isotopes. Because each of these approaches measures slightly different things - atmosphere versus ocean, gases versus isotopes, temperatures hundreds of years ago versus temperatures millions of years ago, seasonal versus annual versus time-averaged temperatures - matching them up with one another and building one continuous record of temperature through Earth’s history is a difficult task. This problem becomes even harder as we move further back in time because our ability to assign an exact age to a measurement decreases. To ensure we make the most accurate measurements possible, each proxy requires a specific expertise in the field and in the lab in addition to an understanding of how these methods work in modern settings through empirical observations and/or experimentation. Because these proxies tell us slightly different stories, scientists applying different methods to the geologic record with the same goal of better understanding and quantifying ancient Earth’s temperatures must collaborate to tell the complete story of our planet’s past. Events like the Paleoclimate Symposium at the Smithsonian's National Museum of Natural History provide forums in which scientists can share their knowledge, discuss these problems, and reach a working consensus as a community.