The Medieval Warm Period In Germany: Inconvenient And very Real

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Hans-Joachim Dammschneider has written a book about the climate history of the southern Harz region. In the historical weather data, he discovered climatic fluctuations that, according to the Intergovernmental Panel on Climate Change (IPCC), should not exist.

Long before industrial CO2 accumulated in the atmosphere, there were already alternating warm and cold phases.

Here is the book description:

The so-called Medieval Warm Period (MWP) has been the subject of scientific debate for years. It is not so much a question of whether this warm period actually took place in Europe, but rather how it took place. Was it a local phenomenon that was limited in time and predominantly restricted to Europe, or was it a period of intense climatic change that also had a global impact?

One thing is certain: from around 950 AD, there was a rise in temperature in Germany lasting at least 300 years, which resulted in a marked warm phase favorable to agriculture and life. However, from the beginning of the 14th century at the latest, this period was replaced by a relatively rapid drop in temperature and climatic turbulence in the direction of the so-called Little Ice Age.

In the early reports, the IPCC (1990, AR1) still devoted relatively much attention to the MWP. Over the years, however, this focus diminished, and in the most recent assessment (2021, AR6) little space was given to the Medieval Warm Period. Studies often even question whether it was a global phenomenon. However, a mapping of the available scientific publications (as of 2022) initiated by S. Lüning shows that the Warm Period certainly left evidence across continents.

From the perspective of natural and cultural history, many accounts show that Germany was in a phase of intense cultural and economic growth from around 1000 AD. This period is characterized by the founding of numerous towns, the expansion of agricultural land and strong population growth. Forests were cleared, building methods influenced, and rising temperatures and the resulting positive agricultural economy contributed to prosperity.

Of course, there were no scientific methods for recording the weather, but modern climate research uses so-called “proxies” to derive the climate parameters of the time. For example, the cultivation of figs north of Cologne, successful wine production as far as Schleswig-Holstein and (overall) the PFISTER index resulting from numerous features indicate a longer phase of mild temperatures and favorable climatic conditions. Climate-numerical backward simulations basically confirm this ‘warm period’.

Historically, such periods were often periods in which life flourished – an idea that plays a rather ambivalent role in the climate debate for the 21st century.

The example of Walkenried Monastery and the southern Harz monastery landscape shows the solid consequences of the MWP: the reclamation of swampy areas, the development of the Upper Harz water management system, the promotion of mining and the intensive use of wood for construction and energy purposes are just a few examples.

However, this phase of monastic prosperity between 1130 and 1300 AD was apparently brought to an end by a rapid drop in temperature. The onset of the ‘Little Ice Age’ brought very uncomfortable weather conditions that lasted until the end of the 18th century. As early as the beginning of the 14th century, the country was hit by destructive rainfall and floods (“Schluchtenreisen” / Magdalenenflut), failed harvests followed intense droughts (Dante anomaly) and devastating plagues with millions of deaths in epidemics partly destroyed social structures. These instabilities and hardships, which were not least determined/induced by the climate, certainly had devastating effects on the livelihoods of the monasteries in the southern Harz region. They led to considerable internal crises (including the loss of converts and lay brothers) and ultimately the end of the Walkenried monastic ‘group’ (with the abandonment of large areas of the Harz ore mining industry) in the 15th century.

If this was the case, what overarching climatic processes contributed to this? It can be assumed that, in addition to temperatures, other factors such as the duration of sunshine also played an important role in the living conditions: The sun indeed seems to have been ‘the’ factor of the MWP, whereas CO2 is that of modern times … .

Recent analyses and the AMO (Atlantic Multidecadal Oscillation) index, which can be traced back to 900 AD, indicate that cyclical SST (Sea Surface Temperature) energy influences from the Atlantic could have significantly influenced cloud cover and thus sunshine duration and temperatures in Europe. These interactions were also important for the southern Harz and Walkenried. Can evaluations of current climatic processes indirectly allow conclusions to be drawn about past physical and social changes with associated phases of ascent and descent between 1000 and 1400 AD?

The present study examines these questions and attempts to draw conclusions for the interactions of the medieval climate from large-scale processes of potential ‘teleconnections’ and oceanic cycles. The book is intended, among other things, as a sequence of steps that helps to better understand the complex interrelationships of medieval climate change. It shows which ‘natural’ parameters could have contributed to the rise and fall of Walkenried Monastery.”

Hans-J. Dammschneider (2025)
Klimageschichte der Südharzer Klosterlandschaft – Kloster Walkenried
ISBN 9783759779878, 106 pages, Hamburg/Norderstedt 2025
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