Great u. s. skepticism of anthropogenic caused climate change among 20 countries, global average about 80% agrees in u. s. while majority agrees, far lower majority compared to other countries. 80s, environmental issues fall on partisan spectrum. Number of climate change skeptics increasing worldwide. 86% of all articles come from u. s. and great britain. What is climate change? greenhouse effect: gases absorb heat. Co2: other than water vapor, most in our atmosphere. N2o: ~265x more effective per ton of co2 emissions. Global warming potential: measure of amount of heat absorbed by 1 ton of gas over a given time period relative to. 1 ton of carbon dioxide product of radiative efficiency and atmospheric residency. Greenhouse gas concentrations and climate positively correlated increases dramatically beginning 1800s technological revolution growing ghg concentrations. May 2013, passed 400 ppm seasonal variation; alters amount of co2 absorbed (hemisphere) evidence for ghg relationship to climate change. Measuring ice cores radio carbon date the layers.