What Went On When it Got Warm?

Examining the

Roman Warm Period

300 BCE-300 CE

Carole L. CrumleyStockholm Resilience Centre

Goals of IHOPE: Map the record of biophysical and human history

• Query correlations: question methods, use multiple lines of evidence• Expect multiple causation• Facilitate interdisciplinary cooperation

Understand the dynamics of linked human/Earth history• Calculate rates of change in system variables• Calibrate models against historic data• What are the emergent properties?

Examine options for the future of humanity• What “lessons” emerge? Examples:

• Path dependence, initial conditions, the multiple roles of diversity • Paleoengineering: enduring solutions to enduring problems

IHOPEIntegrated History and Future of People on Earth

IHOPE Case Studies

• Culture and Economy of SW USA Native American polities and the Drought of the 1300s CE

• Environment And Society in the Maya region of Central America 1000 BCE to 1000 CE

• Environment and Society in Europe from 1000 BCE to 1000 CE

Bracketing the Roman Warm Period When and Where?

• Temporal extent: The Roman Warm Period occurred between ca. 300 BCE and 300 CE; the 1000BCE – 1000CE time frame captures colder, wetter periods on either side

• Spatial extent: E-W From the Ural mountains to the Atlantic Ocean, N-S from Scandinavia to North Africa

• We have only begun to investigate its global extent; we plan to study teleconnections to adjacent regions and around the globe

Study Area

How is the Roman Warm Period Defined?Greenland Ice Core

Estimated Temperature

• A warm, stable period lasting ca. 600 years, roughly paralleling Roman hegemony

• Camp Century shows the clearest signal, but record complicated by changes in ice sheet elevation

• More recent Greenland temperature reconstructions also show high temperatures during Roman period

• Rapid decline begins after 100 AD, falling to the Vandal Minimum, which coincides with the Migration Period (“the Dark Ages”)

Alley QSR 2000

Climate History the Northern Hemisphere and Europe

Land Use and Emission History

• The Bronze Age began 3300BC in the Middle East, thence to India, Europe, China, and Korea

• The Iron Age began in the Near East 1300BC, thence to India and Europe, China, Japan; sub-Saharan Africans independently invented iron technology

• Roman period industrial production was widespread (ceramics, metals, glass, etc)

• On three continents, deforestation for metallurgy, agriculture and wood products began before the Iron Age and accelerated in the Roman period

Estimated Position of the Temperate-Subtropical Ecotone

900-500 BCE 300 BCE-300 CE 500 CE-900 CERoman Warm Period Vandal Minimum

Crumley EA 3:3, 1993

• Hallstatt (ca. 1000-480 BCE) which offers evidence of great wealth in an elite society with long-distance contacts and influence

• La Tène (ca. 480-15 BCE) which ushers in a revolution (regime shift?) in social and political organization and settlement, with an emblematic decorative style

The European Iron Age

At its greatest extent, the Roman Empire

• controlled the Mediterranean Sea and contiguous lands

• covered nearly six million square kilometers

• had an estimated population of sixty-five million people

• a quarter of the planet’s population was under the sway of Rome

The Power of Rome

Roman Imperial Managementand Climate Change

• mono-cropping: many regions were forced to produce grain to feed cities

• erosion, loss of fertility: result of practices to increase short-term yields • deforestation: the need for agricultural land and for ships’ timber • erratic climate devastated harvests after ca. AD 270 • subtropical species: vulnerable in temperate regions• farmland abandoned due to high taxes, low yields and without maintenance reverted to scrub and forest

The Migration Period

300-500 CE: Germanic peoples

500-700 CE: Slavic and Arabic peoples

700-900 CE: Magyar, Turkic, and Viking peoples

“The Vandal Event” “The Dark Ages” “Barbarian Invasions”climatologists Petrarch (14th c.) J. J. Bury

Isotopic RecordLake Holzmaar, Western Germany

High human impact through Iron Age and Roman period disappears with transition into Migration period. Isotopic record suggests that this is a response to colder and/or wetter climatic conditions causing a retreat of people from the catchment area.

Lucke et al 2003

Fluvial GeomorphologyLahn River, West-Central Germany

Peaks in tree trunk deposition coincide with and increased fluvial activity, climate ‘deterioration’ in the Migration period.

Urz, 2002

Questions for Study

• What is the chronology of the Roman Warm Period in Europe? • What are the drivers of the RWP?

NAO? Other?Are there anthropogenic drivers?

• Is the RWP confined to the Mediterranean and temperate Europe? What characterizes the period on other continents? (Gulf of Mexico/Yucatan Peninsula, Eurasian steppe)

• What is the nature of transitional periods that preceded and followed the RWP?

• It appears that the beginning of the Roman Warm Period may haveoccurred in a couple human generations (Dansgaard-Oeschger?)• An inquest on collapse: κ to Ω to α in a coupled CAS

The Roman Warm Period and Global Change Studies

• plentiful data from both qualitative and quantitative disciplines

• a period about which relatively little environmental data are available, despite abundant political, economic, and cultural data

• possibilities for scale-up to N hemisphere or global

• potential for modeling future ecological and cultural refugia in a warming world

• an enthusiastic scholarly community, representing social sciences, humanities, and biophysical sciences

• popular appeal, offering didactic opportunities