Related by context. Frequent words. (Click for all words.) 55 gaseous emissions 53 atmospheric methane 52 methane 51 methanogens 51 CO -2 51 plankton blooms 50 clathrates 50 biogenic 50 phytoplankton blooms 49 nitrous oxide emissions 49 terrestrial ecosystems 49 Co2 48 nitrification 48 bioaccumulation 48 Snowball Earth 48 Ocean acidification 48 abiotic 48 carbon dioxide 48 meteorite impacts 48 prolonged droughts 48 CO2 48 atmospheric CO 48 Earth ozone layer 47 co2 47 atmospheric carbon dioxide 47 hydrological cycle 47 isotope ratios 47 gases emitted 47 atmospheric nitrogen 47 Carbon sequestration 47 species extinctions 47 Ultraviolet radiation 47 Cyanobacteria 47 endocrine disruption 46 nutrient runoff 46 greenhouse gasses 46 atmospheric CO2 46 sulphates 46 greenhouse warming 46 Soil erosion 46 Microorganisms 46 naturally occurring 46 radioactive decay 46 acidify 46 biosphere 46 stratospheric ozone layer 46 hydroxyl radicals 46 Carbon Dioxide 46 carbon dioxide CO2 45 aerosol particles 45 planetesimals 45 N2O 45 mass extinctions 45 ocean acidity 45 acidifying 45 diatoms 45 Photosynthesis 45 planktonic 45 upwellings 45 microbes 45 H#O# 45 isotopic composition 45 naturally occuring 45 CO ² 45 bioenergy crops 45 emmissions 45 microfossils 45 lifeforms 44 manmade 44 biogeochemical 44 carbon sequestration 44 ultra violet radiation 44 anthropogenic 44 Nitrogen oxides 44 Evaporation 44 isoprene 44 permafrost 44 crop residues 44 vertebrate animals 44 temperate zones 44 greenhouse gases 44 megafauna 44 nitrogen fixation 44 Younger Dryas 44 microbiota 44 sequestering carbon 44 volcanism 44 Greenhouse Gases 44 combustion gases 44 melting permafrost 44 polar icecaps 44 Sulfur dioxide 44 saber toothed tigers 44 glaciations 44 nonrenewable resources 44 Mitloehner 44 microorganism 44 desiccation 44 lichen 44 gastropods 43 polycyclic aromatic hydrocarbons PAHs