Related by context. Frequent words. (Click for all words.) 65 Pliocene 64 glaciation 62 Pleistocene 62 Holocene 61 Little Ice Age 58 Eocene 56 Cretaceous 56 Precambrian 54 Ordovician 54 atmospheric CO2 54 Homo sapiens 53 atmospheric carbon dioxide 53 radiocarbon 53 glacial 52 Paleozoic 52 volcanism 52 mass extinctions 52 decadal 52 atmospheric concentrations 52 Ice Age 51 mass extinction 51 Triassic 51 Australopithecus 51 PETM 50 abundances 49 Mesozoic 49 temperate regions 49 greenhouse gas concentrations 49 diatoms 49 equatorial Pacific 49 mid latitudes 49 sediments 48 greenhouse warming 48 hominids 48 epochs 48 geologic 48 megafauna 48 Homo erectus 48 geomagnetic field 48 ENSO 47 permafrost 47 Proterozoic 47 fossils 47 isotopic 46 northern latitudes 46 Neanderthals 46 glaciers 46 sedimentary rock 46 sedimentary rocks 46 Jurassic 46 hominid 46 latitudes 46 volcanic activity 46 sunspot 46 Serreze 45 tetrapods 45 taxa 45 troposphere 45 Miocene 45 sunspots 45 Arctic Ocean 45 geologically 45 Paleolithic 44 single celled organisms 44 plate tectonics 44 Greenland ice 44 #.#C [002] 44 mammoths 44 cyanobacteria 44 seismicity 44 hunter gatherers 44 atmospheric circulation 44 archaea 44 Antarctic Peninsula 44 magmatic 44 olivine 43 extinctions 43 fossil 43 Archaeopteryx 43 Ellesmere Island 43 Antarctic Ice 43 Devonian 43 mountain glaciers 43 glacial ice 43 geomagnetic 43 supernova explosion 43 subduction zones 43 common ancestor 43 speciation 43 Antarctic ice 43 Landsea 43 eukaryotes 43 gigatons 42 influenza pandemics 42 eruptive 42 radioactive decay 42 oscillation 42 upwelling 42 Earth crust 42 El Niño 42 Martian atmosphere