1. Proxy Measurements of Climate Change
Tree rings
Ice cores
Ocean sediments
Pollen records
Corals
Historical records

2. Tree rings
Since tree growth is influenced by climatic conditions, patterns in tree-ring widths, density, and isotopic composition reflect variations in climate. In temperate regions where there is a distinct growing season, trees generally produce one ring a year, and thus record the climatic conditions of each year. Trees can grow to be hundreds to thousands of years old and can contain annually-resolved records of climate for centuries to millennia.
Laboratory of Tree Ring Research at the University of Arizona and the "Ultimate Tree-Ring Web Pages", University of Tennessee

3. Ice cores
Located high in mountains and deep in polar ice caps, ice has accumulated from snowfall over many centuries. 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 the past climate of that area.
To learn more about ice cores please visit the following sites: The Australian Antarctic Division, See Dept. of Glaciology - Issues . The American Geophysical Union Greenland Ice Cores Summit (GISP2) Project

4. Ocean sediments
Ocean & Lake Sediments: 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. Ocean and lake sediments consist of materials that were produced in the lake/ocean or that washed in from nearby land. These materials (preserved tiny fossils and chemicals in the sediments) can be used to interpret past climate.
To learn more about ocean & lake sediments, please visit the following: Ocean Drilling Program; International Marine Global Changes Study.

5. Fossil pollen
Each species and genus of plants produces pollen grains which have a distinct shape. 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 plants 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.
To learn more about fossil pollen, please visit the following: The Institute of Paleontology, University of Vienna, Austria Fossil Groups: Spores and Pollens, U.S. Geological Survey (USGS)

6. Corals
To learn more about the study of corals please visit NOAA's Coral Paleoclimatology Site

7. Historical documents
Historical documents contain a wealth of information about past climates. Observations of weather and climatic conditions can be found in farmers' logs, travellers' diaries, newspaper accounts, and other written records. When properly evaluated, historical data can yield both qualitative and quantitative information about past climate. The example on the right demonstrates how historical grape harvest dates were used to reconstruct summer temperatures (April September) in Paris from [From Bradley, 1990; based on data Le Roy Ladurie and Baulant, 1980.]

8. View a coral core
This is a segment of a coral core obtained from Urvina Bay, Galápagos. The black lines represent annual bands, while the blue and red lines subdivide the year into quarters.

9. ENSO Information from Coral
these corals have recorded recent climate variability, including ENSO events

10. Data from Ice Core
Temperature Anomaly, Vostok Antarctica. Change vs. today in degrees C., in thousands of years before present, derived from deuterium. The record indicates that the Earth has been colder than present for most of the past 250,000 years. Source: J. Jouzel, et al.