Related by context. Frequent words. (Click for all words.) 66 glaciation 64 Little Ice Age 62 Holocene 61 Pleistocene 60 Pliocene 58 volcanism 58 mass extinctions 57 sunspot activity 56 atmospheric CO2 56 atmospheric carbon dioxide 56 mass extinction 55 PETM 55 mid latitudes 55 Eocene 55 Ordovician 55 polar ice 54 megafauna 54 Homo sapiens 54 Ice Age 53 greenhouse warming 53 decadal 52 atmospheric concentrations 52 Cretaceous 52 glaciers 51 mountain glaciers 51 radiocarbon 51 Neandertals 51 greenhouse gas concentrations 51 plate tectonics 51 Antarctic Ice 51 Greenland ice 51 temperate regions 51 Antarctic ice 50 volcanic activity 50 Precambrian 50 Serreze 50 latitudes 50 equatorial Pacific 49 permafrost 49 diatoms 49 glacial ice 49 fossils 49 atmospheric circulation 49 sunspot 49 polar regions 49 Homo erectus 49 Mesozoic 49 aridity 49 Australopithecus 49 supernova explosion 48 mammoths 48 Neanderthals 48 Antarctic Peninsula 48 Triassic 48 homo sapiens 48 sediments 48 glacial 48 anthropogenic 48 sedimentary rock 48 Tibetan Plateau 48 gigatons 47 hominids 47 geologic 47 troposphere 47 fossil 47 martian 47 monsoon rainfall 47 prehistory 47 isotopic 47 tetrapods 47 abundances 47 albedo 47 dinosaurs 46 earths 46 sediment cores 46 tyrannosaurs 46 hominid 46 geomagnetic field 46 Archaeopteryx 46 extinctions 46 earth crust 46 climatological 46 equatorial 46 northern latitudes 46 ringed planet 46 degree centigrade 46 glacier 46 upwelling 46 Arctic Ocean 45 sunspots 45 Paleozoic 45 seismicity 45 olivine 45 radioactive decay 45 hunter gatherers 45 landforms 45 millennia 45 Martian surface 45 tropics 45 Earth crust 45 volcanic eruptions