Reading Climate Records

Scientists reconstruct past climates using natural records called proxies. Tree rings give an annual record spanning thousands of years: wide rings mean good growing conditions, narrow rings record drought, and bristlecone pines preserve over 5,000 years of data.

Coral growth bands work like underwater tree rings, logging ocean temperatures year by year, while ocean sediment layers stretch the record back much further. By combining proxies, scientists built a detailed picture of how Earth's climate has changed and how today's changes compare to the natural record.