July 28, 2009

Global Warming...has it happened before????

Text ColorAccording to about half the hack scientists out there man made global warming is going to wipe out civilization in the next 50 years if we don't start living like cavemen. Now I am not questioning that in the last 150 years until 1998, the planet got warmer. But the question I am presenting is has this warming happened before, why, and what did it lead to? I will try my best to avoid the technobabble that only scientists understand. The question, has global warming happened before? Archaeology and ancient historical records seem to indicate that global warming did happen from 800 to between 1200-1300A.D. For a while, I thought the Roman Catholic church which basically controlled Europe at that time had far too many S.U.V.s but archaeology doesn't bare that out. Here is a wikipedia explanation of this time of Global Warming. I am using wiki because the more scientific sites are generally loaded with technobabble:

The Medieval Warm Period was a time of warm weather around AD 800-1300 during the European Medieval period. Initial research on the MWP and the followingLittle Ice Age (LIA) was largely done in Europe, where the phenomenon was most obvious and clearly documented. It was initially believed that the temperature changes were global.[2] However, this view has been questioned; the 2001 IPCC report summarises this research, saying "…current evidence does not support globally synchronous periods of anomalous cold or warmth over this time frame, and the conventional terms of 'Little Ice Age' and 'Medieval Warm Period' appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries".[3] Global temperature records taken from ice cores, tree rings, and lake deposits, have shown that, taken globally, the Earth may have been slightly cooler (by 0.03 degrees Celsius) during the 'Medieval Warm Period' than in the early- and mid-20th century.[4] Crowley and Lowery (2000) [5] note that "there is insufficient documentation as to its existence in the Southern hemisphere."

Palaeoclimatologists developing region-specific climate reconstructions of past centuries conventionally label their coldest interval as "LIA" and their warmest interval as the "MWP".[4][6] Others follow the convention and when a significant climate event is found in the "LIA" or "MWP" time frames, associate their events to the period. Some "MWP" events are thus wet events or cold events rather than strictly warm events, particularly in central Antarctica where climate patterns opposite to the North Atlantic area have been noticed.

[edit]By world region

[edit]North Atlantic

The last written records of theNorse Greenlanders are from a 1408 marriage in the church ofHvalsey — today the best-preserved of the Norse ruins.

A radiocarbon-dated box core in the Sargasso Sea shows that the sea surface temperature was approximately 1 °C (1.8 °F) cooler than today approximately 400 years ago (the Little Ice Age) and 1700 years ago, and approximately 1 °C warmer than today 1000 years ago (the Medieval Warm Period).[7]

During the MWP wine grapes were grown in Europe as far north as southern Britain.[8][9][10][11] For comparison: today vine is grown in northern Britain, and as far north as Gotland, a Swedish island in the Baltic Sea[12].

[edit]North America

The Vikings took advantage of ice-free seas to colonize Greenland and other outlying lands of the far north.[13] Around 1000AD the climate was sufficiently warm for the north of Newfoundland to support a Viking colony and lead to the descriptor "Vinland". The MWP was followed by the Little Ice Age, a period of cooling that lasted until the 19th century, and the Viking settlements eventually died out. In the Chesapeake Bay, researchers found large temperature excursions during the Medieval Warm Period (about 800–1300) and the Little Ice Age (about 1400–1850), possibly related to changes in the strength of North Atlantic thermohaline circulation.[14] Sediments in Piermont Marsh of the lower Hudson Valley show a dry Medieval Warm period from AD 800–1300.[15]

Prolonged droughts affected many parts of the western United States and especially eastern California and the western Great Basin.[4][16] Alaska experienced three time intervals of comparable warmth: A.D. 1–300, 850–1200, and post-1800.[17] Knowledge of the North American Medieval Warm Period has been useful in dating occupancy periods of certain Native American habitation sites, especially in arid parts of the western U.S.[18] Review of more recent archaeological research shows that as the search for signs of unusual cultural changes during the MCA has broadened, some of these early patterns (e.g. violence and health problems) have been found to be more complicated and regionally varied than previously thought while others (e.g., settlement disruption, deterioration of long distance trade, and population movements) have been further corroborated.[19]

So we have evidence that Global warming is not a new phenomenon and it was not caused by medieval monks driving Chevy Suburbans. Now what did this warming event lead to, what happened when the Previous Warming ended as our current warming period has ended 11 years ago. Could this tell us what the future holds? That will be answered in the following post.

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