[pf] "The warmth is global and cannot be explained by natural forcing me

http://ens.lycos.com/ens/aug2000/2000L-08-18-09.html
 has:

  BOULDER, Colorado, August 18, 2000 (ENS) - A new website on drought
  history is available from the National Geophysical Data Center
  (NGDC) in Boulder. The website, entitled "North American Drought: A
  Paleo Perspective," ( http://www.ngdc.noaa.gov/paleo/drought/ )
  explains how data from sources such as tree rings, lake sediments
  and archeological remains can provide insight about past droughts.
  Rainfall records used to evaluate drought extend back just over 100
  years, and are too short to answer questions about whether
  droughts like the 1930s Dust Bowl are unusual or routine events.
  Data from the natural archive are used to answer these questions
  and to evaluate 20th century North American droughts in the context
  of hundreds to thousands of years in the field of paleoclimatology. 

  Paleoclimatology is the study of past climates that existed before
  humans began collecting instrumental measurements of weather such
  as temperature from a thermometer, precipitation from a rain gauge,
  sea level pressure from a barometer, and wind speed and direction
  from an anemometer. Instead of instrumental measurements of
  weather and climate, paleoclimatologists use natural environmental
  records to infer past climate conditions. Paleoclimatology includes
  the collection of evidence of past climate conditions, and the
  investigation of the climate processes underlying these conditions.
  The new website is the second in NGDC's Paleo Perspectives series
  and follows the successful "A Paleo Perspective on Global Warming"
  ( http://www.ngdc.noaa.gov/paleo/globalwarming/home.html ).
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

**  This last leads to:

http://www.ngdc.noaa.gov/paleo/globalwarming/paleobefore.html
  which has:

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Several periods of warmth (listed below) have been hypothesized to have
occurred in the past. However, upon close examination of these warm
periods, it becomes apparent that these periods of warmth are not similar
to 20th century warming for two specific reasons: 

    1. The periods of hypothesized past warming do not appear to be global in
       extent, or
    2. The periods of warmth can be explained by known natural climatic
forcing
       conditions that are uniquely different than those of the last 100
years.

 Several commonly cited periods of warmth are as follows: 

      The so-called "Medieval Warm Period" (ca., 9th to 14th centuries)
http://www.ngdc.noaa.gov/paleo/globalwarming/medieval.html

      The so-called mid-Holocene "Warm Period" (ca. 6,000 years ago)
http://www.ngdc.noaa.gov/paleo/globalwarming/holocene.html

      The penultimate interglacial period (ca. 125,000 years ago)
http://www.ngdc.noaa.gov/paleo/globalwarming/interglacial.html

      The mid-Cretaceous Period (era?) (ca. 120-90 million years ago)
http://www.ngdc.noaa.gov/paleo/globalwarming/cretaceous.html

 The latest peer-reviewed paleoclimatic studies appear to confirm that the
global warmth of the 20th century may not necessarily be the warmest time
in Earth's history, what is unique is that the warmth is global and cannot
be explained by natural forcing mechanisms.
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sent on by David.
(David MacClement) davd@ihug.co.nz 
http://www.emucities.com.au/member/davd/index.html#top
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