Weather includes the passing of a thunderstorm, hurricane, or blizzard, and the persistence of a heat wave, or a cold snap. Weather variability and extreme events may be an unpredictable response to climate change. Climate is the weather we expect over the period of a month, a season, a decade, or a century. Climate Change is a departure from the expected average weather or climate normals.
Paleoclimatology is the study of past climate.
Paleoclimatology not only includes the collection of evidence of past climate conditions, but the investigation of the climate processes underlying these conditions. Annual records of climate are preserved in tree-rings, locked in the skeletons of tropical coral reefs, frozen in glaciers and ice caps, and buried in the sediments of lakes and oceans. These natural recorders of climate are called proxy climate data - that is they substitute for thermometers, rain gauges, and other modern instruments used to record climate. By analyzing records taken from trees, reefs, glaciers, sediments, and other proxy sources, scientists can extend our understanding far beyond the 140-year instrumental record provided by thermometers and rain gauges. Recent changes in the natural record from environmental proxy data can be calibrated using the 140-year instrumental record of climate change.