climate change climate science global climate climate models climate scientists climate system climate talks global climate change climate sensitivity climate scientist global warming global temperature global temperatures global cooling global economy anthropogenic global warming global mean global economic renewable energy clean energy energy efficiency energy conservation solar energy energy sources energy policy green energy energy use wind energy carbon dioxide carbon emissions carbon tax carbon dioxide emissions carbon footprint carbon trading carbon credits carbon capture low carbon greenhouse gas emissions CO2 emissions carbon dioxide emissions emissions trading emissions trading scheme emissions reductions greenhouse gas natural gas gas prices shale gas gas production gas industry surface temperature global temperature temperature data average temperature temperature record temperature trends temperature rise temperature increase temperature records temperature change sea level sea ice sea levels sea level rise sea surface rising sea levels global sea sea surface temperature sea surface temperatures sea ice extent ocean currents ocean heat ocean acidification ocean temperatures ocean heat content ocean circulation ocean surface ocean temperature deep ocean upper ocean