Carbon Dioxide and Earth's Future Pursuing the ... - Magazooms

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The distribution of studies that allow one to determine whether peak Medieval Warm Period
temperatures were warmer than (red), equivalent to (green), or cooler than (blue), peak
Current Warm Period temperatures. These studies do not include those of the preceding
figure, the blue ones of which should be added to the blue ones of this figure, and the red
ones of which should be added to the red ones of this figure, if true totals of these two result
categories are desired.
The story told by the two figures above seems pretty clear: the peak warmth of the MWP was
typically, but not universally, greater than the peak warmth of the CWP has been to date. And
that earlier period of greater warmth occurred at a time when the atmosphere’s CO2
concentration was fully 100 ppm less than it is today, indicative of the fact that the earth has
experienced equivalent or warmer temperatures than those of the present when there was
much less CO2 in the air, which suggests that whatever was responsible for the greater warmth
of the MWP could easily be responsible for the lesser warmth of the CWP.
In discussing one final large-scale study that did not mix apples and oranges between its early
and later stages, Ljungqvist (2010) developed a 2000-year temperature history of the extratropical
portion of the Northern Hemisphere (i.e., that part covering the latitudinal range 30-
90°N) based on 30 temperature-sensitive proxy records with annual to multi-decadal
resolution, including two historical documentary records, three marine sediment records, five
lake sediment records, three speleothem δ 18 O records, two ice-core δ 18 O records, four varved
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