Roman Warm Period

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The Roman Warm Period was a period of unusually warm weather that ran from approximately 250 BC to 400 AD.[1] Temperatures were approximately 1 degree Celsius warmer than today, according to a study of tree ring data.[2] There was a particularly warm period extending from 21 to 50 AD.[2]

Various proxies have been proposed as evidence for the Roman Warm Period, such as the Roman introduction of vineyards into Britain. Olive presses have been found in the Roman city of Sagalassos in Anatolia, although as of 2000 it was too cold to grow olives in this area of southwestern Turkey.[3]

Writing at the beginning of the Roman Warm Period, Theophrastus (371 – c. 287 BC) wrote that date trees could grow in Greece if planted, but could not set fruit there. This is the same situation as today. It suggests that southern Aegean mean summer temperatures in the fourth and fifth centuries BC were within a degree of modern temperatures. This and other literary fragments from the time confirm that the climate of Greece prior to the Roman Warm Period was basically the same as it was around 2000 AD. Dendrochronological evidence from wood found at the Parthenon shows variability of climate in the fifth century BC resembling the modern pattern of variation.[4] Tree rings from Italy in the late third century BC indicate a period of mild conditions in the area at the time that Hannibal crossed the Alps with elephants.[5]

The phrase "Roman Warm Period" appears in a 1995 doctoral thesis.[6] It was popularized by an article published in Nature in 1999.[7]


  • Pollen: A high resolution pollen analysis of a core from Galicia concluded in 2003 that the Roman Warm Period lasted from 250 BC-450 AD.[1]
  • Glaciers: A 1986 analysis of Alpine glaciers concluded that the 100 AD to 400 AD period was significantly warmer than the immediately preceding and following periods.[8]
  • Deep ocean sediment: A 1999 reconstruction of ocean current patterns based on the granularity of deep ocean sediment concluded there was a Roman Warm Period that peaked around 150 AD.[7]
  • Mollusk shells: An analysis of oxygen isotopes found in mollusk shells in an Icelandic inlet concluded in 2010 that Iceland experienced an exceptionally warm period from 230 BC to 40 AD.[9]

See also


  1. 1.0 1.1 Desprat, S., Goñi, M.F.S. and Loutre, M.-F. 2003. "Revealing climatic variability of the last three millennia in northwestern Iberia using pollen influx data". Earth and Planetary Science Letters 213: 63-78.
  2. 2.0 2.1 "No wonder the Romans could go out in togas during winter", Daily Mail (London), July 12, 2012
    Jan Esper, David C. Frank, Mauri Timonen, Eduardo Zorita, Rob J. S. Wilson, Jürg Luterbacher, Steffen Holzkämper, Nils Fischer, Sebastian Wagner, Daniel Nievergelt, Anne Verstege & Ulf Büntgen, "Orbital forcing of tree-ring data", Nature Climate Change 2, 862–866 (2012)
  3. Scheidel, Morris Saller (2007), p. 19
  4. Scheidel, Morris & Saller 2007, p. 17
  5. Scheidel, Morris Saller (2007), p. 18.
  6. William Paul, "Stable isotopic record of climatic and environmental change in continental settings", 1995, University of Michigan. "The Roman warm period though it has been suggested was responsible in part for advances in civilization, also had a dangerous side."
  7. 7.0 7.1 Bianchi GG, McCave IN, "Holocene periodicity in North Atlantic climate and deep-ocean flow south of Iceland", Nature 397 (6719) 515–7, February 1999.
  8. Röthlisberger, F. (1986). 10,000 Jahre Gletschergeschichte der Erde. Sauerländer. ISBN 3794127978. 
  9. Patterson WP, Dietrich KA, Holmden C, Andrews JT (March 2010). "Two millennia of North Atlantic seasonality and implications for Norse colonies". Proc. Natl. Acad. Sci. U.S.A. 107 (12): 5306–10.