Holocene climatic optimum

Holocene climatic optimum, A global warm period around 9,000–5,000 years ago.

Holocene climatic optimum image

Global warm period around 9,000–5,000 years ago

The Holocene Climate Optimum (HCO) was a warm period during roughly the interval 9,000 to 5,000 years BP, with a thermal maximum around 8000 years BP. It has also been known by many other names, such as Altithermal, Climatic Optimum, Holocene Megathermal, Holocene Optimum, Holocene Thermal Maximum, Hypsithermal, and Mid-Holocene Warm Period.

This warm period was followed by a gradual decline until about two millennia ago.

Contents

Global effects

Temperature variations during the Holocene from a collection of different reconstructions and their average. The most recent period is on the right, but the recent warming is only seen in the inset.

The Holocene Climate Optimum warm event consisted of increases of up to 4:°C near the North Pole (in one study, winter warming of 3 to 9:°C and summer of 2 to 6:°C in northern central Siberia). Northwestern Europe experienced warming, but there was cooling in Southern Europe. The average temperature change appears to have declined rapidly with latitude and so essentially no change in mean temperature is reported at low and middle latitudes. Tropical reefs tend to show temperature increases of less than 1:°C; the tropical ocean surface at the Great Barrier Reef about 5350 years ago was 1:°C warmer and enriched in 18O by 0.5 per mil relative to modern seawater. In terms of the global average, temperatures were probably warmer than now (depending on estimates of latitude dependence and seasonality in response patterns). While temperatures in the Northern Hemisphere were warmer than average during the summers, the Tropics and parts of the Southern Hemisphere were colder than average.

Out of 140 sites across the western Arctic, there is clear evidence for conditions warmer than now at 120 sites. At 16 sites, where quantitative estimates have been obtained, local HTM temperatures were on average 1.6±0.8:°C higher than now. Northwestern North America had peak warmth first, from 11,000 to 9,000 years ago, while the Laurentide Ice Sheet still chilled eastern Canada. Northeastern North America experienced peak warming 4,000 years later. Along the ...read more

Holocene
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Holocene ... Northern Hemisphere until the later date.[citation needed] The Holocene climatic optimum (HCO) was a period of warming in which the global climate became...

Medieval Warm Period
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Interglacial
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Interglacial ... higher than at present. Holocene (12,000 years ago to the present). During the present interglacial, the Holocene, the climatic optimum occurred during the...

8.2-kiloyear event
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8.2-kiloyear event ... cooling was a significant exception to general trends of the Holocene climatic optimum. During the event, atmospheric methane concentration decreased...

Eocene
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Eocene ... temporary reversal of the cooling conditions was the Middle Eocene Climatic Optimum. At around 41.5 million years ago, stable isotopic analysis of samples...

Early human migrations
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Early human migrations ... hypothesis. The Holocene is taken to begin 12,000 years ago, after the end of the Last Glacial Maximum. During the Holocene climatic optimum, beginning about...

Atlantic (period)
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Atlantic (period) ... warmest period of the Holocene, the Atlantic is often referenced more directly as the Holocene climatic optimum, or just climatic optimum. The Atlantic is...

Hans Tausen Ice Cap
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Hans Tausen Ice Cap ... cores show it is around 3500–4000 years old. It formed since the Holocene climatic optimum of 6000-8000 BP. The ice cap is located south of the De Long Fjord...

Climate variability and change
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Climate variability and change ... the Earth is emerging from the latest ice age, cooling from the Holocene climatic optimum and warming from the "Little Ice Age", which means that climate...

Roman Warm Period
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Global temperature record
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Mediterranean Basin
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Early Holocene sea level rise
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African humid period
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Pre-modern human migration
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HCO
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