abrupt climate change agriculture antarctic cold reversal apocalyptic and post-apocalyptic fiction argon asia atlantic ocean beetle before present blytt-sernander cariaco basin carrying capacity cereal climate dendrochronology desert digital object identifier dryas octopetala fifty degrees below forest greenland holocene ice ice core isotope kim stanley robinson lake agassiz levant little ice age loess medieval warm period natufian culture neolithic revolution nitrogen north america norway oak older dryas oldest dryas periglacial pine pleistocene samuel youd scandinavia snow solifluction south america stadial the coming global superstorm the day after tomorrow thermohaline circulation timeline of environmental events timeline of glaciation tundra venezuela younger dryas impact event