Theneoglaciation ("renewedglaciation") describes the documented cooling trend in theEarth's climate during theHolocene, following the retreat of theWisconsin glaciation, themost recent glacial period. Neoglaciation has followed the Hypsithermal orHolocene Climatic Optimum, the warmest point in the Earth's climate during the currentinterglacial stage, excluding theglobal warming-induced temperature increase starting in the 20th century. The neoglaciation has no well-marked universal beginning: local conditions andecological inertia affected the onset of detectably cooler (and wetter) conditions.

Driven inexorably by theMilankovitch cycle, cooler summers in higher latitudes of North America, which would cease to melt the annual snowfall completely, were masked at first by the presence of the slowly disappearing continental ice sheets, which persisted long after the astronomically calculatedmoment of maximum summer warmth: "the neoglaciation can be said to have begun when the cooling caught up with the warming", remarkedE. C. Pielou.^[1] With the close of the "Little Ice Age" (mid-14th to late 19th centuries), neoglaciation appears to have been reversed in the late 20th century, evidently caused byanthropogenicglobal warming. Neoglaciation had been marked by a retreat from the warm conditions of theClimatic Optimum and the advance or reformation ofglaciers that had not existed since the lastice age. In the mountains of western North America, montane glaciers that had melted entirely reformed shortly before 5000BP.^[2] The most severe part of the best documented neoglacial period, especially in Europe and the North Atlantic, is termed the "Little Ice Age".

In North America, neoglaciation had ecological effects in the spread ofmuskeg on flat, poorly drained land, such as the bed of recently drainedLake Agassiz and in theHudson Bay lowlands, in the retreat of grassland before an advancing forest border in theGreat Plains, and in shifting ranges of forest trees anddiagnostic plant species (identified throughpalynology).

InEast Asia, the start of neoglaciation coincided with a major weakening of the East Asian Summer Monsoon (EASM).^[6]

• Neopluvial
• Holocene
• Subboreal