[pf] Man-made global warming in perspective - David's summary.

· Under the _X_X_X_X_ below is part of my earlier post, using NOAA's data.

· This current one is intended to be a rememberable summary, illustrated by
a graph of temperatures since 1000 AD, which shows that we've recently
exceeded the range of temperatures covered by the "error-bars" around the
"Medieval Warm Period" when the Vikings discovered "Vinland" (NE America),
and colonised Greenland's southern shores because they had a Norway-like
climate then.
  It also shows (what to me is the most disturbing aspect of Twentieth
Century global warming), the size and rapidity of the average temperature
increase.
  I'm talking about /measurements/ here, not causes, like CO2 concentration.


· Fact: Temperatures are higher now than in the whole of human history. 
        (That's average temperature of the whole globe.)
        Global Warming is a reality.

· Best estimate: About 50% of the observed global warming is caused by
        greenhouse gas increases due to humans. Although this number
        will continue to be refined, it indicates that the climate modeling
        community is on target with their estimates that the earth may
        warm an additional 2 to 7 degrees F in the next century.


· Those statements, worth remembering, are from NOAA's:
http://www.ngdc.noaa.gov/paleo/globalwarming/end.html ,

  illustrated by this graph (with 2-std.-dev. "error=bars" in yellow) :-
http://www.ngdc.noaa.gov/paleo/globalwarming/images/nhemmill.gif 

  which has a smaller version on its original page: 
http://www.ngdc.noaa.gov/paleo/globalwarming/medieval.html

· I believe they're so valuable that I've got personal copies at:
http://davd.tripod.com/NOAApaleo-end.html#top
http://davd.tripod.com/nhemmill.gif
http://davd.tripod.com/NOAApaleo-medieval.html#top

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_X_

At 16:59 2/9/2000 -0700 (actually sent at 11:24 3/9/2000 +1200),
 I (David Mac) sent to Pos Fut, with Subject: 
"The warmth is global and cannot be explained by natural forcing mechanisms":

>  The new drought website is the second in NOAA's NGDC 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 (via "The Data") to:
>
http://www.ngdc.noaa.gov/paleo/globalwarming/paleobefore.html
>  which has:
>
>- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>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 from 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.
>- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

David.
(David MacClement) davd@ihug.co.nz 
http://www.emucities.com.au/member/davd/index.html#top
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