Related by context. Frequent words. (Click for all words.) 67 greenhouse gases 66 greenhouse gas emissions 64 heat trapping gases 63 carbon dioxide emissions 63 carbon emissions 62 greenhouse emissions 62 greenhouse gasses 60 emissions 60 greenhouse gas 58 greenhouse gas emission 57 GHG emissions 56 tailpipe emissions 55 emission reductions 54 CO2 emissions 53 mercury emissions 53 carbon dioxide 53 reduce carbon emissions 52 carbon emission 51 global warming 51 burning fossil fuels 51 GHG 50 emission 50 reducing carbon emissions 49 emission reduction 49 Emissions 49 fossil fuels 48 mercury pollution 48 CO2 48 climate change 47 carbon dioxide CO2 47 air pollution 47 exhaust emissions 46 nitrogen oxides 46 pollutants 45 pollution 44 atmospheric carbon dioxide 44 nitrogen oxide 43 sulfur dioxide 43 polluters 43 carbon footprints 42 fossil fuel 42 renewable fuels 42 alternative fuels 41 CFCs 41 reduce greenhouse gas 41 Montreal Protocol 41 EPA 40 carbon footprint 40 pollutant 40 Environmental Protection Agency 40 emitters 40 biofuels 40 gases 39 carbon 39 EPA Administrator 39 Kyoto Protocol 39 reducing greenhouse gas 39 climate 39 renewable energy 39 particulate matter 38 nuclear arsenals 38 Concerned Scientists 38 ozone 38 polluter 38 renewables 38 cleaner burning 38 NOx 37 Kyoto treaty 37 nonpartisan Congressional Budget 37 zero emission 37 renewable 37 Climate Change 37 Climate Change UNFCCC 37 hybrid electric 37 methane 37 oceans 36 automobiles 36 acid rain 36 Carbon dioxide 36 Congressional Budget Office 36 Global warming 36 ozone layer 36 electric utilities 36 Copenhagen Accord 36 Climate Change IPCC 36 White House 35 President Barack Obama 35 polar regions 35 Clean Air 35 soot 35 carbon credits 35 environmental impacts 35 Global Warming 35 gas guzzling 35 environmental 35 ecological footprint 35 Copenhagen 35 Kyoto protocol 35 mpg 35 carbon neutral 35 Kyoto