Optimum of Roman times

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The reconstructed global temperature course of the last two thousand years does not give any indications of a simultaneous worldwide Roman warm period lasting several decades

In various periodizations of climatic history, climatic conditions in periods that begin a few decades or centuries before our era and end sometime between the second and fifth centuries of our era are referred to as the optimum of the Roman period (also known as the Roman warm period or climatic optimum of the Roman period ) . Spatially, this usually refers to the climatic conditions of the Mediterranean region and Europe, and occasionally the North Atlantic region or other parts of the world. The name refers to the Roman Empire , whose imperial period (27 BC - 284 AD) largely falls into this period. A connection is often made between the climatic conditions and the conditions in the Roman Empire that were regarded as prosperous at that time.

Concept and delimitation

Development of the snow line of western Norwegian glaciers in the Holocene , according to Liestøl (1960), with a small optimum in “Roman times”; The sketch and name were taken up by Schwarzbach in 1961 and Flohn in 1967 in summaries of Holocene climatic fluctuations

Beginning in the 1960s, in the early days of historical climatology , pioneers in this branch, such as Hubert Lamb or Emmanuel Le Roy Ladurie , proposed periodizations of climate history, which they linked to epochs of traditional European historiography.

The geologists George H. Denton and Vibjörn Karlén made 1973 for the period 450 BC. - 1200 AD. Glacier retreats in the Elias chain ( Alaska ) and in Lapland . They called this phase Roman Empire-Middle Ages warm interval ("warm period between the Roman Empire and the Middle Ages").

In 1979, the climatologist Christian-Dietrich Schönwiese drafted a periodization of the climate history of the Holocene using the work of Hubert Lamb and Hermann Flohn . In it he used the term “optimum of Roman times” - with reference to the climatic conditions in the Alpine region and in North Africa - an epoch from 300 BC. BC to AD 400 as rich in precipitation and similarly warm or warmer than the Medieval Warm Period . He drew parallels to the Roman imperial period from Augustus (31 BC - 14 AD) to the greatest expansion of the Roman Empire (96 AD - 180 AD). Schönwiese expressly pointed out that the term “optimum” should not be misinterpreted in the sense of “globally better climatic conditions” or as “good” in a normative sense. In the periodization, as it can be found in Schönwiese, the optimum of the Roman era is followed by the pessimum of the migration period . This is followed by a medieval warm period with slightly higher average temperatures in the northern hemisphere.

Reid Bryson considered the period 350 BC in a paper in 1988. BC - AD 500 as the Roman optimum.

The term is still used in research in the 21st century. The historian Peregrine Horden describes in a climate-historical summary of Mediterranean antiquity the time 200 BC. BC - 135 AD also as Roman warm period ("Roman warm period").

The American historian Kyle Harper divides the period from the Roman Empire to Late Antiquity into the following epochs: "Roman climatic optimum" (200 BC - 150 AD), Late Roman Transitional Period ("late Roman transition period", 150 AD). AD - 450 AD) and Late Antique Little Ice Age ("Little Ice Age of Late Antiquity", AD 450 - AD 700). Based on this structure, he outlines the development and crises of the Roman Empire and establishes connections between epidemics ( Antonine plague , Cyprian plague , Justinian plague ), climatic fluctuations and historical developments.

Historian John Haldon and others noted in 2018 that such a classification of climate history and its consequences, while rhetorical, does not do justice to the complexity of the material available. Such epochs are gradually being abandoned in research.

Climatic conditions

Global and Northern Hemisphere

About 5000 years ago, especially in the middle and high latitudes of the northern hemisphere, a long-term cooling trend of a little more than 0.1 ° C per millennium began, which continued into the 19th century and was ended by the current anthropogenic global warming . The cause of the cooling trend are changes in the earth's movement relative to the sun ("orbital radiative forcing ", see Milanković cycles ), which have led to reduced solar radiation in the north. Growing snow and ice cover as well as changes in vegetation make the long-term cooling trend visible, especially in the north , through feedback such as ice-albedo feedback . Fluctuations in solar activity and volcanic eruptions, which temporarily cool the climate, as well as internal variability of the climate system superimpose this long-term trend and lead to regionally different climatic fluctuations over a period of years and decades.

Some of the sparsely available global reconstructions suggested rather warm conditions up to the 5th century AD, when low volcanic activity and a comparatively high solar intensity were named as possible causes. More recent reconstructions published in the late 2010s and spanning the past 2000 years incorporate a larger number of climate proxies and gain better global coverage. A global Roman warm period is not recognizable in them. A reconstruction of the temperatures of the last 2000 years north of 30 ° N clearly shows a warmer period from 0–300 AD, which was about 0.1 ° C higher than the mean for the years 1961–1990, but probably lower than 1990– 2010.

Europe and the Mediterranean

Summer temperature anomalies in Europe, 138 BC Chr. - 2003 AD

In Europe it was probably warm, but not too dry. The temperatures afterwards were similar to those of the 20th century, maybe a little warmer north of the Alps, but not as warm as today (1986–2015). Reconstructions made from tree rings show summer temperatures in Europe in the years AD 21–80 that were significantly higher than those in the years 1971–2000. However, temperature reconstructions for this period are subject to considerable uncertainty.

The reconstruction of the hydrological conditions in the Mediterranean area shows a complex, regionally and chronologically differentiated picture of the first and second centuries. Anatolia and the northwest of the Levant, the northeast of the Iberian Peninsula and northern Italy could have been drier than the average for the first millennium, Palestine more humid, in the west of the Iberian Peninsula and Sicily it could have become more humid, and in the western Zāgros Mountains it could have become drier. There is no clear picture for the Balkans.

In addition to volcanic and solar activity, changes in circulation patterns and anthropogenic influences can also be considered as possible causes for regional climate changes. Land use changes could explain warming in parts of North Africa and the Middle East, while aerosol emissions could explain cooling in Central and Eastern Europe.

consequences

In order to prove a climatic influence on historical events and processes, reconstructions are mostly necessary, which give the temperature, precipitation and other climatic data exactly to individual years. However, these are so far only sparsely available, especially for the region of the Roman Empire. Many researchers see the importance of climate and other environmental factors for the history of the Roman period as being undervalued in archeology and historical studies, but at the same time warn against an overestimation (→ climate determinism ).

Edward Gibbon saw in his influential but obsolete historical work The History of the Decline and Fall of the Roman Empire , published from 1776–1789, the Roman history section from the death of Domitian (96 AD) to the sole rule of Commodus (180 AD). ) as the "happiest and most prosperous" time of mankind. The climatic conditions of the region at that time were repeatedly brought into connection with the Roman Empire (27 BC – 284 AD) and especially this historical section.

Agriculture was the most important Roman economic sector . There was a booming trade in agricultural goods in the Mediterranean. Decisive for productivity was u. a. in North Africa and the Levant the availability of water, in Central and Northwest Europe and other regions it was the summer temperatures. The predominantly warm and humid conditions were favorable in large parts of the empire. The supply of the growing population was largely successful.

The retreat of the Alpine glaciers improved the passability of the Alpine passes and made it easier to conquer and integrate Gaul , Germania inferior , Germania superior , Raetia and Noricum into the Roman Empire. From 280 AD, wine was grown in Germania and Britain .

The population also increased in Northern Europe. Increasingly changeable climatic conditions from the end of the second and middle of the third century are associated with military campaigns and migration movements of the time. Warrior and ethnic groups known as Goths , Gepids and Vandals began to advance south in the 2nd and 3rd centuries, opening up new domains and settlements, initially in the Carpathian Mountains and today's southern Russia.

literature

References and comments

  1. ↑ a b PAGES 2k Consortium: Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era . In: Nature Geoscience . July 24, 2019, doi : 10.1038 / s41561-019-0400-0 .
  2. ↑ a b Raphael Neukom, Nathan Steiger, Juan José Gómez-Navarro, Jianghao Wang, Johannes P. Werner: No evidence for globally coherent warm and cold periods over the preindustrial Common Era . In: Nature . July 24, 2019, doi : 10.1038 / s41586-019-1401-2 .
  3. ↑ According to Figure 100 in Olav Liestøl: Glaciers of the present day . In: Olaf Holtedahl (Ed.): Geology of Norway (=  Norges Geologiske Undersökelse . No. 208 ). Oslo 1960.
  4. ↑ Martin Schwarzbach: The climate of prehistoric times: an introduction to paleoclimatology . F. Enke, 1961, Figure 115 (The reference to Liestøl (1960) has been lost in the bibliography of later editions, the graphic continues to be included.).
  5. ↑ Flohn gives as source Schwarzbach (1961): Hermann Flohn: Klimaschwenken in historical time . In: Hans von Rudloff (Hrsg.): The fluctuations and oscillations of the climate in Europe since the beginning of the regular instrument observations . Vieweg, Braunschweig 1967, ISBN 3-540-09635-3 , pp. 85 .
  6. ↑ a b c John Haldon, Hugh Elton, Sabine R. Huebner, Adam Izdebski, Lee Mordechai, Timothy P. Newfield: Plagues, climate change, and the end of an empire: A response to Kyle Harper's The Fate of Rome (1) : Climate . In: History Compass . November 2018, doi : 10.1111 / hic3.12508 .
  7. ↑ George H.Denton and Wibjörn Karlén: Holocene climatic variations - Their pattern and possible cause . In: Quaternary Research . August 1973, doi : 10.1016 / 0033-5894 (73) 90040-9 .
  8. ↑ a b After: Joel D. Gunn: Introduction: A Perspective from the Humanities-Science Boundary . In: Human Ecology . March 1994, doi : 10.1007 / BF02168760 .
  9. ↑ a b c Christian-Dietrich Schönwiese: Climate fluctuations (=  Understandable Science . Volume 115 ). Springer, Berlin, Heidelberg, New York 1979, pp. 75-84 .
  10. ^ A b Christian-Dietrich Schönwiese: Climate changes: data, analyzes, forecasts . Springer, Berlin, Heidelberg, New York 1995, ISBN 3-540-59096-X , pp. 79-92 .
  11. ↑ a b c d e Peregrine Hordes: Mediterranean Antiquity . In: Sam White, Christian Pfister , Franz Mauelshagen (Eds.): The Palgrave Handbook of Climate History . palgrave macmillan, 2018, ISBN 978-1-137-43019-9 , doi : 10.1057 / 978-1-137-43020-5 .
  12. ↑ for the first time so designated by him, see Holdren u. a. (2018)
  13. ↑ Harper uses the term from Büntgen u. a. (2016), but lets the period begin a good 80 years earlier and last 40 years longer, Ulf Büntgen u. a .: Cooling and societal change during the Late Antique Little Ice Age from 536 to around 660 AD . In: Nature Geoscience . March 2016, p. 231-236 , doi : 10.1038 / ngeo2652 .
  14. ^ A b c d e Kyle Harper: Climate, Disease and the Fate of Rome . Princeton University Press, 2017, ISBN 978-0-691-16683-4 .
  15. ↑ Information from Paleoclimate Archives: Observed Recent Climate Change in the Context of Interglacial Climate Variability and Regional Changes During the Holocene - Temperature - Northern Hemisphere Mid-to-High Latitudes . In: Intergovernmental Panel on Climate Change [IPCC] (Ed.): Fifth assessment report (AR5) . 2013, 5, Executive Summary, and 5.5.1.1.
  16. ↑ Shaun A. Marcott: A Reconstruction of Regional and Global Temperature for the Past 11,300 Years . In: Science . tape 339 , March 8, 2013, doi : 10.1126 / science.1228026 .
  17. ↑ Heinz Wanner , L. Mercolli, M. Grosjean and SP Ritz: Holocene climate variability and change; a data-based review . In: Journal of the Geological Society . 2014, doi : 10.1144 / jgs2013-101 .
  18. ↑ Robert Tardif, Gregory J. Hakim, Walter A. Perkins, Kaleb A. Horlick, Michael P. Erb, Julien Emile-Geay, David M. Anderson, Eric J. Steig, David Noone: Last Millennium Reanalysis with an expanded proxy database and seasonal proxy modeling . In: Climate of the Past . July 2019, doi : 10.5194 / cp-15-1251-2019 .
  19. ↑ Fredrik Charpentier Ljungqvist: A new reconstruction of temperature variability in the extra-tropical northern hemisphere during the last two millennia . In: Geografiska Annaler: Series A, Physical Geography . No. 3 , 2010, doi : 10.1111 / j.1468-0459.2010.00399.x .
  20. ↑ a b J Luterbacher u. a .: European summer temperatures since Roman times . In: Environmental Research Letters . 2016, doi : 10.1088 / 1748-9326 / 11/2/024001 ( HTML ).
  21. ↑ PAGES 2k Network: Continental-scale temperature variability during the past two millennia . In: Nature Geoscience . tape 6 , no. 5 , February 2013, p. 339-346 , doi : 10.1038 / ngeo1797 ( nature.com ).
  22. ↑ Anina Gilgen, Stiig Wilkenskjeld, Jed O. Kaplan, Thomas Kühn, Ulrike Lohmann: Effects of land use and anthropogenic aerosol emissions in the Roman Empire . In: Climate of the Past . October 2019, doi : 10.5194 / cp-15-1885-2019 .
  23. ^ A b c Henry Diaz, Valerie Trouet: Some Perspectives on Societal Impacts of Past Climatic Changes . In: History Compass . 2014, doi : 10.1111 / hic3.12140 .
  24. ↑ John Haldon, Hugh Elton, Sabine R. Huebner, Adam Izdebski, Lee Mordechai, Timothy P. Newfield: Plagues, climate change, and the end of an empire: A response to Kyle Harper's The Fate of Rome (2): Plagues and a crisis of empire . In: History Compass . November 2018, doi : 10.1111 / hic3.12506 .
  25. ^ Ellsworth Huntington: Climatic Change and Agricultural Exhaustion as Elements in the Fall of Rome . In: The Quarterly Journal of Economics . February 1917, doi : 10.2307 / 1883908 .