Friday, June 28, 2013

Analysis finds the Medieval Warming Period was global and unrelated to CO2

A new paper from SPPI & CO2 Science:

[Illustrations, footnotes and references available in PDF version]
The Medieval Warm Period (MWP) was a global climatic anomaly that encompassed a few centuries on either side of AD 1000, when temperatures in many parts of the world were even warmer than they are currently. The degree of warmth and associated changes in precipitation, however, varied from region to region and from time to time; and, therefore, the MWP was manifest differently in different parts of the world. How it behaved in Russia is the subject of this Summary.
In contradiction of another of Mann et al.'s contentions, Krenke and Chernavskaya went on to unequivocally state - on the basis of the results of their comprehensive study of the relevant scientific literature - that “the Medieval Warm Period and the Little Ice Age existed globally.”
The fact that the warming that brought the world the Current Warm Period began around 1750 AD, or nearly 100 years before the modern rise in atmospheric CO2 concentration, should be evidence enough to argue that the planet's current warmth is the result of nothing more than the most recent and expected upward swing of this natural climatic oscillation.
From approximately AD 1200 to 1410, they concluded that temperatures in the region of their study were “probably higher than today,” providing yet another example of times and places when and where low-CO2 Medieval Warm Period temperatures were likely higher than high-CO2 Current Warm Period temperatures.

In conclusion, and considering the full spectrum of studies included in this Summary, it would appear that a goodly portion of the Medieval Warm Period throughout Russia was somewhat warmer than what has so far been experienced there during the Current Warm Period. And since the MWP held sway when the atmosphere's CO2 concentration was something on the order of 285 ppm, as compared to the 400 ppm of today, it would appear that the air's CO2 content has had essentially nothing to do with earth's near-surface air temperature throughout the entire Holocene, when the air's CO2 concentration at times dropped as low as 250 ppm. Other factors have clearly totally dominated.


  1. I cannot find any evidence in the entire paleoclimate record that CO2 has any effect on climate. The results of this paper are not a bit surprising. There are sufficient negative feedbacks to the addition of CO2 so as to negate any effect that CO2 has on climate. These negative feedbacks are provided by good old H2O that dominates the greenhouse effect.

  2. Paleozoic had the greatest diversity and quantity of life. Also the greatest capture of carbon out of the air. Followed by snowball earth during Neoproterozoic. It was not till the escape of carbon during the continental brake up did life return to earth. The reality is the world has warmed sence the last ice age and that has been a great improvement for all life on earth. The reduction of diversity has more to do with people population than climate. And nothing to do with carbon. Increased CO2 means increased plant growth and increased food supply. Warmer does not drier. It means wetter.
    Medieval Warm Period was climate wise much better growing season.
    The return of Paleozoic epoch would be much better than even a small ice age. The problem is CO2 has little to do with it.

  3. We can only conclude one thing: CO2 is good for the earth, considering fotosynthesis and the fact that CO2 has no measurable influence on the temperatures on earth.

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