As a climatologist, I am frequently told by people skeptical about climate change that “the climate is always changing.” Of course, climatologists know this because we were the ones that discovered those changes in the first place with the collaboration of paleobotanists, chemists, geologists and other scientists. We also know that the climate of the past was very different from the climate on earth today and that the changes we are seeing now are unlike changes that have occurred in the past in how fast things are changing. This article from NASA describes some of the ways that we know what the climate of past eons was using tools like tree rings, pollen and ice cores, and rock types. Take a look at see what information you can gather from these different sources at https://climate.nasa.gov/explore/evidence-for-earths-past-climate/ .
