1. Studying Past Climates

2. Studying Climate in the past
Paleoclimatologists study past climates
They use Proxy records; which are stores of information in tree rings, ice cores and fossils that can be measured to give clues to what the climate was like in the past

3. Ice Cores
Ice in Greenland and Antarctica contains air bubbles that have been trapped for thousands of centuries
Scientists drill deep into the ice and extract long cylinders of ice
The ice at the top of the ice core is recent and the bottom ice can be up to years old

5. Ice Cores
Scientist cut ice cores into very thin slices and test the air bubbles in each slice for various gases
This measures the amount of carbon dioxide, methane and nitrous oxide that was in the air when the bubble formed
Ice cores have shown scientists that the concentration of these greenhouse gases has changed dramatically over Earth’s history

6. Ice Cores
Scientists can also obtain information about the earth’s temperature, precipitation and volcanic eruptions through preserved layers of dust in an ice core
Ice cores tell scientists that the earth’s climate has gone through many changes in climate (including warmer and colder periods)

7. Tree Rings When a tree grows, it creates one growth ring per year
The rings are the thickest during the years of good growing conditions
Some trees live for thousands of years and scientists can assemble clues from living and dead trees about the climate during that time

9. Coral Reefs Like trees, coral reefs add layers of growth each season
Scientists drill cylinders of coral and study their layers
Information from coral layers help determine the temperature of the surface ocean water when each layer was growing

11. Rock, Caves and Ocean Sediment
Layers of soil and rock build up on the earth over time and each layer gives clues, such as plant or fossils to the climate at that time
Sediment cores from the ocean floor contain clues that provide data about past climates

13. Summary
Proxy records are indirect records of past climates contained in natural materials
Analyzing air bubbles in ice cores provides data on greenhouse gases temperature from the past
Analyzing the growth rings on ancient trees and coral provides data on temperature and precipitation from the past