-The study of changes in climate taken on the scale of the entire history of earth.
-Proxy: a source of climate information from natural archives which can be used to estimate climate conditions prior to the modern period.
So How exactly is it Measured?
- Each year, a tree adds a layer of wood
- Trees grow more quickly when warm and moist=wider rings
- Trees grow more slowly and when cold and dry=smaller rings
- Corals add seasonal layers
- Thickness of layers change due to a combination of temperature, water clarity, and nutrient availability
- The higher the ratio of O18 to O16 in corals=colder temperature
- Layering thickness indicates the amount of precipitation
- bubbles in ice are used to measure the composition of air
- the higher the ratio of O18 to O16 in ice cores=warmer temperature
- particles from volcanic ash or pollution indicate major historical events
- may contain preserved plants, animals, or pollen, which can be characteristic of certain climates
- High Mg/Ca ratio of preserved species=high temperature
- Greater occurance of C13-O18 bonds=low temperature