Learn how plants respond to higher atmospheric CO2 concentrations

How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic


The Roman and Medieval Warm Periods at Paradise Lake, Northwestern Himalaya
Reference
Bhattacharyya, A., Sharma, J., Shah, S.K. and Chaudhary, V. 2007. Climatic changes during the last 1800 yrs BP from Paradise Lake, Sela Pass, Arunachal Pradesh, Northeast Himalaya. Current Science 93: 983-987.

What was done
The authors developed a relative history of atmospheric warmth and moisture covering the last 1800 years for the region surrounding Paradise Lake -- which is located in the Northeastern Himalaya at approximately 2730.324'N, 9206.269'E -- based on pollen and carbon isotopic (δ13C) analyses of a one-meter-long sediment profile they obtained from a pit "dug along the dry bed of the lakeshore."

What was learned
Bhattacharyya et al. report that their climatic reconstruction revealed a "warm and moist climate, similar to the prevailing present-day conditions," around AD 240 -- which would represent the last part of the Roman Warm Period -- as well as another such period that turned out to be "more warmer [our italics] 1100 yrs BP (around AD 985) corresponding to the Medieval Warm Period."

What it means
The existence of these two periods -- the former of which was at least as warm as the present, and the latter of which was actually warmer than the present -- occurring at times when the atmosphere's CO2 concentration was more than 100 ppm less than it is today, clearly suggests that today's warmth could well be due to a repeat performance of whatever it was that produced the equally high and higher temperatures, respectively, of these two earlier warm periods. And this study is but one of many distributed throughout the world that suggest the very same thing, as illustrated by the data we have archived in our Medieval Warm Period Project. Therefore, with each passing week, literally (because we post a new such study in each week's new issue of CO2 Science), it becomes ever more difficult for climate alarmists to claim that our current warmth is unprecedented over the past two millennia or more, and that it must thus be due to anthropogenic CO2 emissions.

Reviewed 23 January 2008