What are proxy data, and why are they necessary in the study of climate change?

Proxy data is the data that is gathered from natural recorders of climate variability, such as tree rings, ice cores, and ocean-floor sediments. The proxy data are necessary in the study of climate change because it helps in the understanding of the climate of the past for the purpose of assessing the current and potential future climate in the context of natural climate variability. 

Bruh i don’t know the answer tbh but you can google it