How do we know what the weather was like thousands of years ago? We didn’t have weather satellites or atmospheric probes. We didn’t even have thermometers!
Understanding historic climate is a super hard problem, but it’s also a really important one. After all, we need to know what the climate used to be like to figure out how it’s changing in response to global warming.
The good news is that there are clues about ancient climate hidden everywhere, from the rings of super old trees to ice packed deep underground. To understand these clues, scientists need to use almost every field of science.
For example, we can use fossil records of reptiles to see if a region used to be tropical, but we need to understand biology enough to know if an ancient crocodile could survive a snowstorm. Or we could study the composition of different layers of sediment, but we need to understand chemistry and physics enough to know how relative concentrations of isotopes change over time. We could even look to myths, folklore, and oral tradition to try to piece together the weather experienced by ancient civilizations.
One scientist who is hunting for clues about ancient climate is a paleoclimatologist named Kathleen Johnson. Dr. Johnson studies rocks found deep inside the cool darkness of caves, and studies their chemical properties to understand what the Earth was like when those rocks formed. By peeling back the layers of the slow-growing rock formations, she can trace climate shifts across the millenia.
Read the post on Dr. Johnson's amazing research, and then do the activity below to see what you learned. If you don't know the answer, do some research on your own to see if you can figure it out!