Related by context. Frequent words. (Click for all words.) 62 Medieval Warm Period 61 Little Ice Age 52 Pliocene 50 Holocene 49 Cretaceous Period 49 glaciation 49 Late Cretaceous 49 sunspot activity 47 Pleistocene 46 volcanism 46 atmospheric concentrations 46 atmospheric carbon dioxide 46 mass extinctions 45 atmospheric CO2 45 aridity 45 El Ninos 45 glacial melt 45 desiccation 44 diatoms 44 CO2 concentrations 44 greenhouse warming 43 stratospheric ozone 43 #.#C [002] 43 greenhouse gas concentrations 43 temperate zones 43 troposphere 43 Quaternary 43 atmospheric circulation 43 Climatic 43 anthropogenic 43 Carboniferous 42 Fertile Crescent 42 decadal 42 abundances 42 volcanic activity 42 diatom 42 climatic 42 fourteenth century 42 isotopic 42 temperate regions 42 lake sediments 42 ozone depletion 42 megafauna 42 PETM 42 temperatures 42 radioactive decay 41 El Niño 41 #AD [002] 41 Sunspots 41 species extinctions 41 eutrophication 41 Droughts 41 acidification 41 mass extinction 41 nitrogen fixation 41 mid latitudes 40 Mesoamerica 40 Neolithic 40 Han Dynasty 40 ° C 40 Byzantine Empire 40 salinity 40 º C 40 cyanobacteria 40 volcanic eruptions 40 Humid 40 sunspots 40 biogenic 40 arid regions 40 Industrial Revolution 40 Qinghai Tibet Plateau 40 coral bleaching 40 Tibetan Plateau 40 sulfur dioxide SO2 39 degree centigrade 39 sediment cores 39 polar regions 39 ozone concentrations 39 aerosol particles 39 North Atlantic Oscillation 39 degrees Fahrenheit 39 thirteenth century 39 geomagnetic field 39 oxygen depletion 39 Greenland Ice 39 albedo 39 radiocarbon 39 upwelling 38 plate tectonics 38 oscillation 38 epochs 38 Middle Ages 38 Neandertals 38 El Niño phenomenon 38 equatorial Pacific 38 El Nino phenomenon 38 Temperature 38 degrees centigrade 38 dinosaurs roamed 38 colonization 38 hunter gatherers