The Roman Warm Period, or Roman Climatic Optimum, was a period of unusually-warm weather in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

and the

North Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe and ...

that ran from approximately 250 BC to AD 400.

Theophrastus Theophrastus (; grc-gre, Θεόφραστος ; c. 371c. 287 BC), a Greek philosopher and the successor to Aristotle in the Peripatetic school. He was a native of Eresos in Lesbos.Gavin Hardy and Laurence Totelin, ''Ancient Botany'', Routledge ...

(371 – c. 287 BC) wrote that date trees could grow in

Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders with ...

if they were planted but that they could not set fruit there. That is still the case today, which implies that

South Aegean The South Aegean ( el, Περιφέρεια Νοτίου Αιγαίου, translit=Periféria Notíou Eyéou, ) is one of the thirteen administrative regions of Greece. It consists of the Cyclades and Dodecanese island groups in the central and ...

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 Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...

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 Hannibal's crossing of the Alps in 218 BC was one of the major events of the Second Punic War, and one of the most celebrated achievements of any military force in ancient warfare.Lancel, Serge, ''Hannibal'', p71/ref> Hannibal managed to l ...

with imported elephants in 218 BC. Dendrochronological evidence from wood found at the

Parthenon The Parthenon (; grc, Παρθενών, , ; ell, Παρθενώνας, , ) is a former temple on the Athenian Acropolis, Greece, that was dedicated to the goddess Athena during the fifth century BC. Its decorative sculptures are considere ...

shows variability of climate in the 5th century BC, which resembles the modern pattern of variation. Cooling at the end of the period is noted in

Southwest Florida Southwest Florida is the region along the southwest Gulf coast of the U.S. state of Florida. The area is known for its beaches, subtropical landscape, and winter resort economy. Definitions of the region vary, though its boundaries are generally ...

, which may have been caused by a reduction in solar radiation reaching the Earth. That may have triggered a change in atmospheric circulation patterns. The phrase "Roman Warm Period" first appears in a 1995 doctoral thesis. It was popularized by an article published in ''

Nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...

'' in 1999. 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 The Little Ice Age (LIA) was a period of regional cooling, particularly pronounced in the North Atlantic region. It was not a true ice age of global extent. The term was introduced into scientific literature by François E. Matthes in 1939. Ma ...

" and "

Medieval Warm Period The Medieval Warm Period (MWP), also known as the Medieval Climate Optimum or the Medieval Climatic Anomaly, was a time of warm climate in the North Atlantic region that lasted from to . Proxy (climate), Climate proxy records show peak warmth oc ...

," were regional phenomena, not globally-coherent episodes. That analysis uses the

temperature record of the last 2,000 years The temperature record of the last 2,000 years is reconstructed using data from climate proxy records in conjunction with the modern instrumental temperature record which only covers the last 170 years at a global scale. Large-scale reconstruct ...

dataset compiled by the .

Proxies

Pollen

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 The Iberian Peninsula (), ** * Aragonese and Occitan: ''Peninsula Iberica'' ** ** * french: Péninsule Ibérique * mwl, Península Eibérica * eu, Iberiar penintsula also known as Iberia, is a peninsula in southwestern Europe, defi ...

Glaciers

A 1986 analysis of

Alpine Alpine may refer to any mountainous region. It may also refer to: Places Europe * Alps, a European mountain range ** Alpine states, which overlap with the European range Australia * Alpine, New South Wales, a Northern Village * Alpine National Pa ...

glaciers concluded that the period from AD 100 to 400 was significantly warmer than earlier and later centuries. Artifacts recovered from the retreating

Schnidejoch The ''Schnidejoch'' is a mountain pass in the Bernese Alps, at above sea level, cutting across the ridge connecting the Schnidehorn and the Wildhorn. Archaeological artifacts, their dates spread over six millennia (from the Neolithic to the ...

glacier have been taken as evidence for the

Bronze Age The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second pri ...

, Roman, and Medieval Warm Periods.

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.

Mollusk shells

An analysis of oxygen isotopes found in mollusk shells in an Icelandic inlet concluded in 2010 that

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...

experienced a warm period from 230 BC to AD 140.

Notes

References

*. Corrigendum: . *. *, in . * (pb: ). *. *. * *. *. *. *. *. *. * * {{cite journal , author=PAGES 2k Consortium, title=A global multiproxy database for temperature reconstructions of the Common Era - Scientific Data , journal=Scientific Data , date=11 July 2017 , volume=4 , issue=1 , page=170088 , doi=10.1038/sdata.2017.88 , pmid=28696409 , pmc=5505119 , ref={{sfnref , PAGES 2k Consortium , 2017 __NOTOC__ 1990s neologisms 1995 introductions 1995 in science History of climate variability and change 1st millennium BC 1st millennium in Europe Climate of Europe