Evidence of Past Climates

By: Dayou Liu, Jacky Liao, Michelle Dong, Emily Zagrodney

Climate Change Statistics

Major changes in climate around 330 000 BCE, 240 000 BCE, and 125 000 BCE
Climate affected by natural causes
Resulted in carbon dioxide concentration being 280ppm
During that time, the rate of increase was rapid
Carbon dioxide (CO₂) is a greenhouse gas
Patterns were found in global temperatures. The temperature increased about 1.5°C

Ice cores contain evidences of past cliamtes
These cores can contain carbon dioxide, methane, and nitrous oxide
These can be used to determine the composition of the air when these cores are formed

Characteristics of rocks are different depending on the environment in which they are deposited
Some rocks were deropped by glaciers, meaning the climate was cold
Rocks that form in hot desert environments are often red because they contain iron
If hot enough, sea water can evaourate, leaving behind a layer of salt

The pollen and spores are useful for determining past climates
Pollen and spores have different shapes, allowing us to determine which plant it came from
Different plants adapt to different climates, so by observing it we can tell which climate they live in

When glaciers moved in the rivers in UK, they carved out a U shape
Glaciers pick up rock and gravel and they scratch the ground, this creates striations.

Climates can be analyzed through palyntology, the study of fossil pollen

Fossils are left in layers, allowing scientists to estimate the rough time period in which they were left

Plants serve as good indicators as they are immobile, unlike animals

Certain plants are very climate-specific; they are only found in specific types of climates

Leaves in warmer, wetter climates are larger and thicker

Colder, drier climates result in thinner, smaller leaves

Aquatic species are affected by water salinity, temperature, and light levels

Forams (shelled creatures) vary depending on temperature, so their fossils are a good indicator of temperature

Foram shells contain information on water content (oxygen level, etc.)

Coral builds shell from calcium carbonate, taken from seawater, containing oxygen and trace metals

Historical data shows period of unusual warmth between 900 and 1300 BC, followed by cooler temperatures

Indentations and flat portions in land are caused by heavy ice sheets/cold climates
Norwegian Fjords created by the ice moving down the river, plowing away the banks
Creates a "U" shape

Records all factors affecting tree growth
Includes factors such as moisture, temperature, minerals in the soil
Wide rings indicate a good growing season, and narrow rings indicate othewise
Trees in temperate zones don't record winters
Trees in tropical zones are hard to analyze, as growth is constant
Comparison with other types of trees in the area show a detailed report of past climates
Dead/older trees can be analyzed and compared to younger trees, rings should line up