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Dust Deposits at the Bottom of the Aral Sea
Huang, X., Oberhansli, H., von Suchodoletz, H. and Sorrel, P. 2011. Dust deposition in the Aral Sea: implications for changes in atmospheric circulation in central Asia during the past 2000 years. Quaternary Science Reviews 30: 3661-3674.

What was done
Working with an 11.12-meter sediment core they obtained from Asia's Aral Sea, the authors calculated bulk sediment fluxes and analyzed grain-size distributions of detrital sediments over the past two millennia at high time-resolution (which was provided by radiocarbon dating and archeological evidence), after which they compared their results with the temperature history of the Northern Hemisphere produced by Mann and Jones (2003), with an emphasis "placed on the variations at the transition from the Medieval Warm Period (MWP) to Little Ice Age (LIA) since this period is the most pronounced climatic transformation during the last millennium, citing in this regard the studies of Yang et al. (2002), Trouet et al. (2009) and Chen et al. (2010).

What was learned
According to Huang et al., they found "a remarkably low deposition [of dust] during AD 1-350," which would have been part of the Roman Warm Period, "a moderately high value from AD 350-720," which corresponds to the Dark Ages Cold Period, "a return to a relatively low level between AD 720 and AD 1400," which includes the Medieval Warm Period, "an exceptionally high deposition from AD 1400 to the 1940s," which includes the Little Ice Age, and what they refer to as "an abnormally low value since the 1940s," when the Current Warm Period may be considered to have begun.

What it means
As the four researchers explain it, the temporal variations in the dust deposition are consistent with the changes in the "mean atmospheric temperature of the northern hemisphere during the past 2000 years, with low/high annual temperature anomalies corresponding to high/low dust supplies in the Aral Sea sediments, respectively," which finding reinforces the reality of a non-CO2-induced millennial-scale cycling of earth's surface air temperature, and thus provides no need whatsoever for any greenhouse-gas-induced phenomenon to explain the planet's current level of warmth or when it began.

Chen, F.H., Chen, J.H., Holmes, J., Boomer, I., Austin, P., Gates, J.B., Wang, N.L., Brooks, S.J. and Zhang, J.W. 2010. Moisture changes over the last millennium in arid central Asia: a review, synthesis and comparison with monsoon region. Quaternary Science Reviews 29: 1055-1068.

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

Trouet, V., Esper, J., Graham, N.E., Baker, A., Scourse, J.D. and Frank, D.C. 2009. Persistent positive north Atlantic oscillation mode dominated the medieval climate anomaly. Science 324: 78-80.

Yang, B., Brauning, A., Johnson, K.R. and Shi, Y.F. 2002. General characteristics of temperature variation in China during the last two millennia. Geophysical Research Letters 29: 10.1029/2001GL014485.

Reviewed 9 May 2012