evidence_d

By Kaylee, Janet and Rachel

Ice Core Sediments:
- Like marine sediment cores, an ice core provides a vertical timeline of past climates stored in ice sheets and mountain glaciers.

- The seasonal snow layers are easiest to see in snow pits. To see the layers, scientists dig two pits separated by a thin wall of snow. One pit is covered, and the other is left open to sunlight. By standing in the covered pit, scientists can study the annual snow layers in the snow wall as the sunlight filters through the other side. - Scientists drill long cores out of the ice sheets. Records going back about 750,000 years have come out of Antarctica. - The ice cores can provide an annual record of temperature, precipitation, atmospheric composition, volcanic activity, and wind patterns. The ratio of oxygen isotopes in the snow reveals temperature, though in this case, the ratio tells how cold the air was at the time the snow fell. In snow, colder temperatures result in higher concentrations of light oxygen. - Ice cores can also record the atmosphere’s characteristics.
 * Method:**

- Only provides direct evidence about temperature and rainfall where ice still exists, though they hint at global conditions. - Marine sediment cores cover a broader area—nearly 70 percent of the Earth is covered in oceans—but they only give tiny hints about the climate over the land. - Soil and rocks on the Earth’s surface reveal the advance and retreat of glaciers over the land surface, and fossilized pollen traces out rough boundaries of where the climate conditions were right for different species of plants and trees to live. - Unique water and rock formations in caves harbor a climate record of their own.
 * Limitations:**

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Summary of Sea Sediment Measurements:
Sea sediments research as Evidence for Climate Change -made of organic and in organic materials: [|Source]
 * Includes the remnants of sea-dwelling plankton
 * Technique takes the ocean temperature from the past 100 years
 * Used continental drifts that impact climate change
 * Uses inorganic material that has been compressed into the ocean floor
 * Uses the inorganic material to provide information about the past and how wet or dry the continents were from the wind that moved the currents[|UN source link]

Summary of Tree Ring Measurements:
In a tree the cambium, (the cells that will become wood or bark), grow in a light layer during late spring/early summer changing to a dark layer in later summer/early fall. The light layer is **early wood**, formed when the tree is growing rapidly. The dark layer is **late wood** and is grown more slowly. The growth occurs at the outside of the trunk, just under the bark, so that a light and dark ring pair represents one year. These annual rings can be counted to tell the age of the tree The growth patterns can be studied to determine the conditions a tree lived through such as forest fires, drought, insect attack, floods, or slopes. The study of tree rings and climate is called dendroclimatology. An instrument called an increment borer is drilled into the tree. This extracts a piece of wood about the size of a drinking straw that shows the growth rings. The growth of a tree's annual rings is related to the weather in the area. If it has been a dry summer a tree does not grow very much during that and the following year or two. If it was a wet summer than there is more growth.

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**Temperature indicators:**
General discussion of the uncertainties of Global Warming: media type="youtube" key="VJM0goE7sr0" width="425" height="350"

Graph containing natural temperature changes, human impact, and observed temperatures since the late 1800's: media type="youtube" key="S9ob9WdbXx0" width="425" height="350"

Graphs: Temperature Change


The graph below correlates the increase in carbon dioxide with an increase in temperature.



Summary of Information
The following graph shows comparisons for various types of indicators - temperature (red), as well as tree rings, corals, ice cores and historical records (blue).