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CO2Science's Medieval Warm Period Project
Volume 9, Number 4: 25 January 2006

With this issue of CO2 Science, we launch our Medieval Warm Period Project, wherein each week we describe, analyze, tabulate and plot (on both graphs and maps) the findings of a different peer-reviewed scientific journal article that describes this multi-century period of significant warmth that occurred about a thousand years ago.

Why did we institute the project?
Climate alarmists claim that temperatures over the latter part of the 20th century were higher than those experienced at any other time over the past one to two millennia, based primarily on the work of (Mann et al. (1998, 1999) and Mann and Jones (2003).  Their reason for doing so is to use this claim to support their related claim that anthropogenic CO2 emissions from the burning of fossil fuels have caused dramatic global warming, which if allowed to continue will produce a number of catastrophic consequences.  We intend to disprove the first of these claims, so as to remove support for the second claim, by demonstrating that about 1000 years ago, when there was approximately 25% less CO2 in the atmosphere than there is currently, temperatures throughout the entire world were equally as high as (or even higher than) they were over the latter part of the 20th century.  This real-world data-based fact should conclusively demonstrate that there is nothing unnatural about the planet's current level of warmth, and that it is likely caused by the recurrence of whatever cyclical phenomenon created the equal or even greater warmth of the Medieval Warm Period.

What elements comprise the project?
The first element of our Medieval Warm Period Project is a tabular listing of all Study Descriptions and Results, which are organized under separate subheadings for each of the world's seven continents.  Within each of these subheadings there are (or ultimately will be) three tables: one for Level 1 Studies, one for Level 2 Studies, and one for Level 3 Studies.  The first of these categories is comprised of studies where the scientists who conducted the work (not us) provide quantitative data that enable one to determine the degree by which the peak temperature of the Medieval Warm Period (MWP) differed from the peak temperature of the Current Warm Period (CWP).  The second category is comprised of studies where the scientists who conducted the work provide qualitative data that enable one to determine which of the two periods was warmer, but not by how much.  The third category is comprised of studies where the MWP was evident in the study's data, but where the data did not provide a means by which the warmth of the MWP could be compared with that of the CWP.

The second element of our MWP Project is a graphical representation of the quantitative results of all Level 1 studies, where we present a plot of the frequency distribution of all MWP-CWP Temperature Differentials.  The third element is an Interactive Map and Time Domain Plot of all of the studies' results.  The map, which can be viewed at different degrees of magnification, pinpoints the locations of all studies in the project's database, identifies each study's level of sophistication (1, 2 or 3), and provides a link to each study's particulars in the Study Descriptions and Results part of the project, while just below the map is a graph of the frequency distribution of the time intervals over which the MWP was determined to have occurred.  Last of all, the fourth and fifth elements of the project are simply lists of all of the scientists and research institutions involved with the work of the several studies, which comprise, respectively, our List of Scientists Whose Work We Cite and List of Research Institutions Associated With the Work We Cite.

What will be accomplished by the project?
Our Medieval Warm Period Project will ultimately host a readily-accessible collection of totally independent databases that far exceeds the number of databases employed in the long-term temperature reconstructions that are used by climate alarmists to promote their claim that the latter part of the 20th century was warmer than any other similar period of the past one to two millennia.  And from what we already know, based on information currently in our possession, our Medieval Warm Period Project will clearly demonstrate the invalidity of this claim, as the evidence we present continues to accumulate ... week after week after week.

Sherwood, Keith and Craig Idso

Mann, M.E., Bradley, R.S. and Hughes, M.K.  1998.  Global-scale temperature patterns and climate forcing over the past six centuries.  Nature 392: 779-787.

Mann, M.E., Bradley, R.S. and Hughes, M.K.  1999.  Northern Hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations.  Geophysical Research Letters 26: 759-762.

Mann, M.E. and Jones, P.D.  2003.  Global surface temperatures over the past two millennia.  Geophysical Research Letters 30: 10.1029/2003GL017814.