What was done
Working on the Swina barrier at the southern end of the Baltic Sea, which consists of two sandy spits or depositional landforms (Wolin and Uznam) that extend outward from the seacoast, Riemann et al. established what they describe as "a detailed and reliable chronology" of these landforms, based on optically stimulated luminescence (OSL) dating of the coastal sediment succession, where the sediment history was derived from the degree of podzolisation, which is based on the much earlier work of Keilhack (1912), who "sub-divided these dunes into three generations (brown, yellow and white) and established a 'classic' dune classification system for the southern Baltic Sea coast." And this sediment history reveals much about the climate history of the region.

What was learned
The five researchers report that following the Roman Warm Period, which they say "is known for a moderate and mild climate in Europe" that produced brown foredunes, there is a hiatus between the brown and yellow dunes from 470 AD to 760 AD that "correlates with a cold and stormy period that is known as the Dark Ages Cold Period," which they say "is well known as a cooling event in the climatic records of the North Atlantic (Bond et al., 1997; McDermott et al., 2001) and in marine sediment cores from Skagerrak (Hass, 1996)," and which is also associated with a phase of increased aeolian activity in northeast England reported by Wilson et al. (2001).

Next, as expected, comes the Medieval Warm Period. And last of all, Riemann et al. write that "the cold and stormy Little Ice Age (Hass, 1996) correlates to the formation of the transgressive white dune I in the sediment successions, which were dated to between 1540 and 1660 AD," adding that "the Little Ice Age is documented in North and West Europe in plenty of coastal dunefields, and resulted in sand mobilisation and development of transgressive dunes (e.g., Clemmensen et al., 2001a,b, 2009; Wilson et al., 2001, 2004; Clarke et al., 2002; Ballarini et al., 2003; Clemmensen and Murray, 2006; Aagaard et al., 2007; Sommerville et al., 2007; Clarke and Rendell, 2009)," due to a colder climate and increased storminess related to periodic shifts of the North Atlantic Oscillation (Dawson et al., 2002).

What it means
Noting that "the systematic accretion of foredunes is accompanied by a moderate climate and a progressive plant cover," the German and Polish scientists go on to say that foredune instability is "related to aeolian sand mobilisation within phases of a decreased plant cover caused by colder and stormier conditions." And thus it is that numerous sets of dune-derived data bear witness to the millennial-scale climate oscillation that has sequentially brought the world the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period, the Little Ice Age and the Current Warm Period naturally, without any need to invoke a similarly oscillating atmospheric CO2 concentration, which further suggests that the Current Warm Period would likely have developed as it has even if the Industrial Revolution and its associated anthropogenic CO2 emissions had never occurred. And on another note, the results of Reimann et al., together with those of the many other researchers they cite, clearly demonstrate that in this particular part of the world warming brings less storminess, in contradiction of the common climate-alarmist claim that it typically does just the opposite.

References
Aagaard, T., Orford, J. and Murray, A.S. 2007. Environmental controls on the coastal dune formation; Skallingen Spit, Denmark. Geomorphology 83: 29-47.

Ballarini, M., Wallinga, J., Murray, A.S., van Heteren, S., Oost, A.P., Bos, A.J.J. and van Eijk, C.W.E. 2003. Optical dating of young coastal dunes on a decadal time scale. Quaternary Science Reviews 22: 1011-1017.

Bond, G., Showers, W., Cheseby, M., Lotti, R., Almasi, P., deMenocal, P., Priore, P., Cullen, H., Hajdas, L. and Bonani, G. 1997. A pervasive millennial-scale cycle in North Atlantic Holocene and Glacial climates. Science 278: 1257-1266.

Clarke, M.L. and Rendell, H.M. 2009. The impact of North Atlantic storminess on western European coasts: a review. Quaternary International 195: 31-41.

Clarke, M., Rendell, H., Tastet, J.-P., Clave, B. and Masse, L. 2002. Late-Holocene sand invasion and North Atlantic storminess along the Aquitaine Coast, southwest France. The Holocene 12: 231-238.

Clemmensen, L.B. and Murray, A. 2006. The termination of the last major phase of aeolian sand movement, coastal dunefields, Denmark. Earth Surface Processes and Landforms 31: 795-808.

Clemmensen, L.B., Pye, K., Murray, A. and Heinemeier, J. 2001a. Sedimentology, stratigraphy, and landscape evolution of a Holocene coastal dune system, Lodbjerg, NW Jutland, Denmark. Sedimentology 48: 3-27.

Clemmensen, L.B., Murray, A., Beck, J.H. and Clausen, A. 2001b. Large-scale aeolian sand movement on the west coast of Jutland, Denmark in late Subboreal to early Subatlantic time -- a record of climate change or cultural impact? Geologiska Foreningens i Stockholm Forhandlingar 123: 193-203.

Clemmensen, L.B., Murray, A., Heinemeier, J. and de Jong, R. 2009. The evolution of Holocene coastal dunefields, Jutland, Denmark: a record of climate change over the past 5000 years. Geomorphology 105: 303-313.

Dawson, A.G., Hickey, K., Holt, T., Elliott, L., Dawson, S., Foster, I.D.L., Wadhams, P., Jonsdottir, I., Wilkinson, J., McKenna, J., Davis, N.R. and Smith, D.E. 2002. Complex North Atlantic Oscillation (NAO) index signal of historic North Atlantic storm-track changes. The Holocene 12: 363-369.

Hass, H.C. 1996. Northern Europe climate variations during late Holocene: evidence from marine Skagerrak. Palaeogeography, Palaeoclimatology, Palaeoecology 123: 121-145.

Keilhack, K. 1912. Die Verlandung der Swinepforte. Jahrbuch der Konigliche-Preussischen Geologischen Landesanstalt XXXII: 209-244.

McDermott, F., Mattey, D.P. and Hawkesworth, C. 2001. Centennial-scale Holocene climate variability revealed by a high-resolution speleothem ¹⁸O record from SW Ireland. Science 294: 1328-1331.

Sommerville, A.A., Hansom, J.D., Housley, R.A. and Sanderson, D.C.W. 2007. Optically stimulated luminescence (OSL) dating of coastal aeolian sand accumulation in Sanday, Orkney Islands, Scotland. The Holocene 17: 627-637.

Wilson, P., Orford, J.D., Knight, J., Braley, S.M. and Wintle, A.G. 2001. Late-Holocene (post-4000 years BP) coastal dune development in Northumberland, northeast England. The Holocene 11: 215-229.

Wilson, P., McGourty, J. and Bateman, M.D. 2004. Mid- to late-Holocene coastal dune event stratigraphy for the north coast of Northern Ireland. The Holocene 14: 406-416.