Roman Warm Period

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Roman Warm Period
Topographic map of the area affected by the Roman Warm Period, specifically Europe and the NE North Atlantic Ocean
The Roman Warm Period affected Europe and the North Atlantic Ocean.
Duration250 BC – AD 400
LocationEurope and the North Atlantic

The Roman Warm Period, or Roman Climatic Optimum, was a period of unusually-warm weather in Europe and the North Atlantic that ran from approximately 250 BC to AD 400.[1] Theophrastus (371 – c. 287 BC) wrote that date trees could grow in Greece if they were planted but that they could not set fruit there. That is still the case today, which implies that South Aegean mean summer temperatures in the 4th and the 5th centuries BC were within a degree of modern ones. That and other literary fragments from the time confirm that the Greek climate was basically the same then as around 2000. Tree rings from the Italian Peninsula in the late 3rd century BC indicate a time of mild conditions there around the time of Hannibal's crossing of the Alps with imported elephants in 218 BC.[2]

Dendrochronological evidence from wood found at the Parthenon shows variability of climate in the 5th century BC, which resembles the modern pattern of variation.[3]

Cooling at the end of the period is noted in Southwest Florida, which may have been caused by a reduction in solar radiation reaching the Earth. That may have triggered a change in atmospheric circulation patterns.[4]

The phrase "Roman Warm Period" first appears in a 1995 doctoral thesis.[5] It was popularized by an article published in Nature in 1999.[6]

More recent research, including a 2019 analysis based on a much larger dataset of climate proxies, has found that the putative period, along with other warmer or colder pre-industrial periods such as the "Little Ice Age" and "Medieval Warm Period," were regional phenomena, not globally-coherent episodes.[7] That analysis uses the temperature record of the last 2,000 years dataset compiled by the PAGES 2k Consortium 2017.[7]



A high-resolution pollen analysis of a core from Galicia concluded in 2003 that the Roman Warm Period lasted from 250 BC to AD 450 in northwestern Iberia.[8]


A 1986 analysis of Alpine glaciers concluded that the period from AD 100 to 400 was significantly warmer than earlier and later centuries.[9] Artifacts recovered from the retreating Schnidejoch glacier have been taken as evidence for the Bronze Age, Roman, and Medieval Warm Periods.[10]

Deep ocean sediment[edit]

A 1999 reconstruction of ocean current patterns, based on the granularity of deep ocean sediment, concluded that there was a Roman Warm Period, which peaked around AD 150.[6]

Mollusk shells[edit]

An analysis of oxygen isotopes found in mollusk shells in an Icelandic inlet concluded in 2010 that Iceland experienced a warm period from 230 BC to AD 140.[11]

See also[edit]


  1. ^ Cambell, Ian D; Campbell, Celina; Apps, Michael J; Rutter, Nathaniel W; Bush, Andrew BG (1998). "Late Holocene similar to 1500yr climatic periodicities and their implications". Geology. 26: 471–473. doi:10.1130/0091-7613(1998)026<0471:LHYCPA>2.3.CO;2.
  2. ^ Sallares 2007, p. 18.
  3. ^ Sallares 2007, p. 17.
  4. ^ Wang, Ting; Surge, Donna; Walker, Karen Jo (2013). "Seasonal climate change across the Roman Warm Period/Vandal Minimum transition using isotope sclerochronology in archaeological shells and otoliths, southwest Florida, USA". Quaternary International. 308–309: 230–241. Bibcode:2013QuInt.308..230W. doi:10.1016/j.quaint.2012.11.013.
  5. ^ Patterson, William Paul (1995). Stable isotopic record of climatic and environmental change in continental settings (PhD thesis). Ann Arbor: University of Michigan. hdl:2027.42/104848. OCLC 712737306. The Roman warm period though it has been suggested was responsible in part for advances in civilization, also had a dangerous side.
  6. ^ a b Bianchi GG, McCave IN; McCave (February 1999), "Holocene periodicity in North Atlantic climate and deep-ocean flow south of Iceland", Nature, 397 (6719): 515–7, Bibcode:1999Natur.397..515B, doi:10.1038/17362, S2CID 4304638
  7. ^ a b Werner, Johannes P.; Wang, Jianghao; Gómez-Navarro, Juan José; Steiger, Nathan; Neukom, Raphael (July 2019). "No evidence for globally coherent warm and cold periods over the preindustrial Common Era" (PDF). Nature. 571 (7766): 550–554. Bibcode:2019Natur.571..550N. doi:10.1038/s41586-019-1401-2. ISSN 1476-4687. PMID 31341300. S2CID 198494930.
  8. ^ Desprat, S.; Goñi, M.F.S.; 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 (1–2): 63–78. Bibcode:2003E&PSL.213...63D. doi:10.1016/S0012-821X(03)00292-9.
  9. ^ Röthlisberger, F. (1986), 10,000 Jahre Gletschergeschichte der Erde, Sauerländer, ISBN 978-3794127979
  10. ^ Imogen Foulkes, Alpine melt reveals ancient life, BBC News, 24 August 2008.
  11. ^ 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, Bibcode:2010PNAS..107.5306P, doi:10.1073/pnas.0902522107, PMC 2851789, PMID 20212157