Holocene climatic optimum
[6] The 2021 IPCC report expressed medium confidence that temperatures in the last decade are higher than they were in the Mid-Holocene Warm Period.
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.
Northwestern North America reached peak warmth first, from 11,000 to 9,000 years ago, but the Laurentide Ice Sheet still chilled eastern Canada.
[15] In the southwestern Iberian Peninsula, forest cover reached its peak between 9,760 and 7,360 years BP as a result of high moisture availability and warm temperatures during the HCO.
[19] The onset of the HCO in the southern Ural Mountains was simultaneous with that in Northern Europe, while its termination occurred between 6,300 and 5,100 BP.
[30] Pollen records from Lake Tai in Jiangsu, China shed light on increased summer precipitation and a warmer and wetter overall climate in the region.
That was caused by a strengthening of the African monsoon by changes in summer radiation, which resulted from long-term variations in the Earth's orbit around the Sun.
[40] It is hypothesized that humans played a role in altering the vegetation structure of North Africa at some point after 8,000 years ago by introducing domesticated animals, which contributed to the rapid transition to the arid conditions that are now found in many locations in the Sahara.
[41] Further south, in Central Africa, the savannas that make up the coastal lowlands of the Congo River drainage basin in the present were entirely absent.
[44] In the far Southern Hemisphere (New Zealand and Antarctica), the warmest period during the Holocene appears to have been roughly 10,500 to 8,000 years ago, immediately after the end of the last ice age.
[50] A comparison of the delta profiles at Byrd Station, West Antarctica (2164 m ice core recovered, 1968), and Camp Century, Northwest Greenland, shows the post-glacial climatic optimum.
[51] The Renland ice core from East Greenland apparently covers a full glacial cycle from the Holocene into the previous Eemian interglacial.
The calculated Milankovitch Forcing would have provided 0.2% more solar radiation (+40 W/m2) to the Northern Hemisphere in summer, which tended to cause more heating.
[citation needed] However, orbital forcing would predict maximum climate response several thousand years earlier than those observed in the Northern Hemisphere.
The delay may be a result of the continuing changes in climate, as the Earth emerged from the last glacial period and related to ice–albedo feedback.
