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Weather, Climate, and Paleoclimatology


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climate_paleo.gif, stock photos

What is weather?

Weather is the state of atmospheric conditions (i.e., hot/cold, wet/dry, calm/stormy, sunny/cloudy) that exist over relatively short periods of time (hours to a couple of days). 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 such as floods and droughts, may be an unpredictable response to climate change.

For more information on weather and extreme events please see the following:

What is Climate?

Climate is the weather pattern we expect over the period of a month, a season, a decade, or a century. More technically, climate is defined as the weather conditions resulting from the mean, or average, state of the atmosphere-ocean-land system, often described in terms of "climate normals" or average weather conditions. Climate Change is a departure from the expected average weather or climate normals.

What is Paleoclimatology?

Paleoclimatology is the study of past climate. The word is derived from the Greek root "paleo-," which means "ancient," and the term "climate." Old Leaf image, stock photo Paleoclimate is that which existed before humans began collecting instrumental measurements of weather (e.g., temperature from a thermometer, precipitation from a rain gauge, sea level pressure from a barometer, wind speed and direction from an anemometer). Instead of instrumental measurements of weather and climate, paleoclimatologists use natural environmental (or "proxy") records to infer past climate conditions. Paleoclimatology not only includes the collection of evidence of past climate conditions, but the investigation of the climate processes underlying these conditions.

For more study of paleoclimatology please visit the following:

How do we measure paleoclimate?

paleo data image courtesy of NOAA and Paleo Slide Sets 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.

What can Paleoclimatology tell us about climate change relevant to society in the future?

To understand and predict changes in the climate system, we need a more complete understanding of seasonal to century scale climate variability than can be obtained from the instrumental climate record. The instrumental temperature record indicates that the Earth has warmed by 0.5°C (0.9°F) from 1860 to the present. However, this record is not long enough to determine if this warming should be expected under a naturally varying climate, or if it is unusual and perhaps due to human activities. Paleoclimatic proxy data can be used to extend climate records and provide a longer time frame (hundreds to tens of thousands of years) for evaluating the warming of the last 140 years.

The cause of global warming over the last century remains a heated debate with significant economic and societal implications. Many scientists attribute the current global warming to the enhancement of the greenhouse effect by human activities. Other scientists have suggested that other factors not affected by humans, such as changes in the number and size of volcanic eruptions or an increase in the sun's output (such phenomena are referred to as climate forcings), are responsible. A paleoclimate perspective provides information about long term changes in different climate forcings that may be the underlying cause of the observed climate change.

An analogy of how paleoclimatic data improves our understanding of climate can be explained in terms of the stock market. Stock market analysts use longer term trends (one, two, three, or six months) in the stock market indexes (DOW, NASDAQ, etc.) rather than depending on changes from one day to the next or over a week to predict what the market will do next (i.e., Bull or Bear Market). In much the same way, the paleoclimate perspective allows us to evaluate climate change many decades and centuries into the past, in order to develop a more reliable estimate of how climate may change in the future.

The paleoclimate perspective can help us answer many questions, including...

  • Is the last century of climate change unprecedented relative to the last 500, 2000, and 20,000 years?
  • Do recent global temperatures represent new highs, or just part of a longer cycle of natural variability?
  • Is the recent rate of climate change unique or commonplace in the past?
  • What does it mean if the last century is unprecedented in terms of warming?
  • Can we find evidence in the paleoclimate record for mechanisms or climate forcings that could be causing recent climate change?
On to... "The Data"
Back to... "How do we study Global Warming?"

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Last Updated Wednesday, 20-Aug-2008 11:23:45 EDT by paleo@noaa.gov
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