1. 8.11 Studying Clues to Past Climates
Paleoclimatologists study past climate using proxy records such as fossils, tree rings, ice cores, and coral reefs.
Ice Cores
Ice cores drilled in Antarctica and Greenland contain trapped air bubbles.
Studying these air bubbles gives information about concentrations of greenhouse gases and air temperature at the time the bubbles formed.
Ice cores provide records going back years.
Scientists have learned the following information from ice cores:
Concentrations of greenhouse gases have changed dramatically over Earth’s history.
Temperature and greenhouse gas concentrations increase and decrease at the same time.
Earth has gone through many changes in climate, from ice ages to interglacial periods, and back to ice ages.
proxy records

2. 8.11 Studying Clues to Past Climates Tree Rings
Studying tree rings gives information on growing conditions at the time each ring formed (for example, a warm wet year versus a cold dry year).
Tree rings provide records going back years.
Coral Reefs
Scientists drill cylinders of coral and study their layers.
Studying coral layers gives information on ocean temperature at the time each layer grew.
Rock
Layers of rock contain clues, such as plant pollen or fossils, to the climate at the time and place where the rock formed.

3. 8.11 Studying Clues to Past Climates Ocean Sediment
Scientists drill sediment cores from the ocean floor.
The layers in sediment cores contain fossils and other clues that provide evidence of different climates over time.
Caves
In caves, rock formations grow as the minerals dissolved in dripping water solidify into rock.
Scientists can measure and date rock layers in caves to obtain information on how much precipitation occurred at different times in the past.