1. Studying Past Climates

2. Climate Records
Scientists have recorded data like temperature and rainfall for the last or so years
Before that people kept informal records such as journals, paintings and farming records.
What do we do when we want to know what the climate was like 1000, , or 1 million years ago?

3. Proxy records
Proxy Records: 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
Proxy records are indirect  they do not give us quantitative measurements of temperature, precipitation etc.
Instead, we can compare them to quantitative measurement to determine what they represent.

4. Ice Cores
In Greenland and Antarctica there are air bubbles that have been preserved in the ice for hundreds of thousands of years.
By drilling into the ice and extracting long cylinders, called cores, scientists can test these bubbles to see which gases are present (e.g. to look at concentrations of greenhouse gases.
Different types of oxygen atoms frozen in the ice can indicate changes in temperatures
In colder air there are more atoms of light oxygen
Ice can also hold a record of volcanic activity, if there is frozen dust and ash

5. Tree Rings Trees produce one new ring per year
In years with good growing conditions (warm and wet) the rings will be wider than in years with poor growing conditions (dry and cold).
Some tress can grow for thousands of years.
By combining tree ring data from living and dead tree, scientists have been able to create records that go back as far as year.

6. Coral Reefs Coral also grow in annual layers.
By drilling out cylinders of coral, scientists can learn about the ocean temperature when each layer grew

7. Fossils
Organisms are usually adapted to their environment, so when organisms are preserved as fossils it gives scientists clues about what the climate might have been like
Pollen preserved in rocks is especially useful, because it tells scientists what plants were able to live in the environment at that time.
Fossilized ocean life can also give clues about the temperature and depth of the ocean

8. Cave Formations
Dripping water in caves can lead to the formation of structures called stalactites and stalagmites.
These structures grow in layers that can be measured and dated
The formations grow faster in rainy weather, so that can give information about how much precipitation happened at specific times in the past