To learn more about the study of corals please visit NOAA's Coral Paleoclimatology Site . These shapes can be used to identify the type of plant from which they came. Since pollen grains are well preserved in the sediment layers that form in the bottom of a pond, lake or ocean, an analysis of the pollen grains in each layer tell us what kinds of plant were growing at the time the sediment was deposited. Inferences can then be made about the climate based on the types of plants found in each layer. Trees can grow to be hundreds to thousands of years old and can contain annually-resolved records of climate for centuries to millennia.
Scientists drill through the deep ice to collect ice cores.
These cores contain dust, air bubbles, or isotopes of oxygen, that can be used to interpret past climate of that area. Between 6 and 11 billion metric tons of sediment accumulate in the ocean and lake basins each year. Scientist drill cores of sediment from the basin floors.