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

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and the

North Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for ...

that ran from approximately 250 BC to AD 400.

Theophrastus Theophrastus (; ; c. 371 – c. 287 BC) was an ancient Greek Philosophy, philosopher and Natural history, naturalist. A native of Eresos in Lesbos, he was Aristotle's close colleague and successor as head of the Lyceum (classical), Lyceum, the ...

(371 – c. 287 BC) wrote that

date tree ''Phoenix dactylifera'', commonly known as the date palm, is a flowering-plant species in the palm family Arecaceae, cultivated for its edible sweet fruit called dates. The species is widely cultivated across northern Africa, the Middle East, ...

s could grow in

Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...

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 (, ) is one of the thirteen administrative regions of Greece. It consists of the Cyclades and Dodecanese island groups in the central and southeastern Aegean Sea. Administration The South Aegean region was established in ...

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 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 led his Ancie ...

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

Parthenon The Parthenon (; ; ) is a former Ancient Greek temple, temple on the Acropolis of Athens, Athenian Acropolis, Greece, that was dedicated to the Greek gods, goddess Athena. Its decorative sculptures are considered some of the high points of c ...

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 genera ...

, 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 is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...

'' 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. Mat ...

" 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 about to about . Climate proxy records show peak warmth occu ...

," were regional phenomena, not globally-coherent episodes. That analysis uses the temperature record of the last 2,000 years 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 ( ), also known as Iberia, is a peninsula in south-western Europe. Mostly separated from the rest of the European landmass by the Pyrenees, it includes the territories of peninsular Spain and Continental Portugal, compri ...

Glaciers

A 1986 analysis of Alpine glaciers concluded that the period from AD 100 to 400 was significantly warmer than earlier and later centuries. Artifacts recovered from the retreating Schnidejoch glacier have been taken as evidence for the

Bronze Age The Bronze Age () was a historical period characterised principally by the use of bronze tools and the development of complex urban societies, as well as the adoption of writing in some areas. The Bronze Age is the middle principal period of ...

, 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 a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

experienced a warm period from 230 BC to AD 140.

Citations

General and cited references

* . Corrigendum: . * . * . (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 , bibcode=2017NatSD...470088E __NOTOC__ 1990s neologisms 1995 in science 1995 introductions 1st millennium BC 1st millennium in Europe Climate of Europe History of climate variability and change