Climatologists look at patterns of climate in the past to understand how climate is affected by things such as the presence or absence of mountains, the effects of moving continents, changes in ocean circulation, and changes in solar energy. Science News has an interesting article this week on the Pliocene period about 3 million years ago and what it can tell us about what the climate might be like in the future. You can read it at https://www.sciencenews.org/article/what-pliocene-epoch-can-teach-us-about-future-warming-earth.