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In page Atlantic (period):

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The Atlantic in palaeoclimatology was the warmest and moistest Blytt–Sernander period, pollen zone and chronozone of Holocene northern Europe. The climate was generally warmer than today[citation needed]. It was preceded by the Boreal, with a climate similar to today's, and was followed by the Subboreal, a transition to the modern. Because it was the warmest period of the Holocene, the Atlantic is often referenced more directly as the Holocene climatic optimum, or just climatic optimum.