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]
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]
Glaciers
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
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
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]
^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.
^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.
^Röthlisberger, F. (1986), 10,000 Jahre Gletschergeschichte der Erde, Sauerländer,
ISBN978-3794127979
Huang S, Pollack HN, Shen PY (4 July 2008), "A late Quaternary climate reconstruction based on borehole heat flux data, borehole temperature data, and the instrumental record", Geophysical Research Letters, 35 (13), L13703,
Bibcode:
2008GeoRL..3513703H,
doi:10.1029/2008GL034187,
hdl:2027.42/95180,
S2CID11399172.
Mann, Michael E.; Zhang, Zhihua; Hughes, Malcolm K.; Bradley, Raymond S.; Miller, Sonya K.; Rutherford, Scott; Ni, Fenbiao (9 September 2008), "Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia", Proceedings of the National Academy of Sciences of the United States of America, 105 (36): 13252–13257,
Bibcode:
2008PNAS..10513252M,
doi:10.1073/pnas.0805721105,
PMC2527990,
PMID18765811.
Mann, Michael E.; Zhang, Zhihua; Rutherford, Scott; Bradley, Raymond S.; Hughes, Malcolm K.; Shindell, Ddrew; Ammann, Caspar M.; Faluvegi, Greg; Ni, Fenbiao (27 November 2009), "Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly", Science, 326 (5957): 1256–1260,
Bibcode:
2009Sci...326.1256M,
doi:
10.1126/science.1177303,
PMID19965474,
S2CID18655276.
Ljungqvist, F. C.; Krusic, P. J.; Brattström, G.; Sundqvist, H. S. (2012), "Northern Hemisphere temperature patterns in the last 12 centuries", Climate of the Past, 8 (1): 227–249,
Bibcode:
2012CliPa...8..227L,
doi:10.5194/cp-8-227-2012.