On the coherence of natural climate cycles of the past 1ka in multiple proxies from central Europe, the Arctic and east Asia.

Abstract:

While the cooling of global temperatures through the Little Ice Age from 1300CE is clearly documented in a large number of proxies, the existence of natural cycles with periods of order 200 years is less clear, other than as local or regional phenomena. We use six proxy temperature records and find evidence for synchronicity of ~200-year cycles in the northern hemisphere. The first two data sets are (1) a reconstruction from an ice core in the Colle Gnifetti (CG) glacier on the Swiss-Italian border (Bohleber et al 2018), and (2) length records of the Great Aletsch glacier (GAG), Switzerland (Holzhauser, 2009). A third is a proxy (3) by Cabedo-Sanz et al (2016) using the biomarker IP25 in sea sediments north of Iceland, which serves as a proxy for drift ice and hence arguably for Arctic ice areal coverage. Further temperature proxies for (4) all-China (Ge et al, 2017), (5) north China and (6) central China (Wang et al, 2018) provide a distribution of coverage over the non-tropical northern hemisphere. These six regional temperature proxy data sets are also compared with the G7 global temperature reconstruction (Ludecke and Weiss, 2017).

Prominent minima in temperature proxy data occur circa 1350CE (all 6 proxies), 1480-1520CE (4 proxies), 1650-1700CE (all 6 proxies) and 1800-1860CE (all 6 proxies). The last three of these are also visible in the G7 global temperature reconstruction. Since 1600CE we note that CG temperatures and IP25 Arctic ice counterintuitively lag GAG glacier length variations by about 50 years; this may reflect precipitation variations in the Alps preceding the temperature drop, or it may be attributable to uncertainties in age dating between the data sets.

The dominant centennial periods in the data sets are in the range 240-180 years and ~470 years which within dating uncertainties may relate to the 208-year de Vries cycle and a possible 510 year cycle previously recognized in solar activity and in terrestrial cosmogenic isotopes.