What’s causing global warming?

World average temperature 1880-2014
Credit: NASA/Bloomberg

Scientists agree that the world is warming, & that human activity is substantially the cause.^1,2,3,4

1.4 °F (0.8 °C) since 1880.⁵

Climate change deniers have claimed a number of other possible causes:
● changes in the Earth's orbit
● changes in the output of the Sun
● volcanic emissions
● land use
● ozone pollution
● aerosols

Researchers at NASA have looked at the impact of all of these, separately & together, to reveal the combined outcome.

https://www.bloomberg.com/graphics/2015-whats-warming-the-world/
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¹ “Scientific consensus: Earth's climate is warming”, http://climate.nasa.gov/scientific-consensus/

² “The 97% consensus on global warming”, https://www.skepticalscience.com/global-warming-scientific-consensus.htm

³ “How to Determine the Scientific Consensus on Global Warming”, http://www.scientificamerican.com/article/how-to-determine-the-scientific-consensus-on-global-warming/

⁴ “Survey finds 97% of climate science papers agree warming is man-made“, http://www.theguardian.com/environment/climate-consensus-97-per-cent/2013/may/16/climate-change-scienceofclimatechange

⁵ “Graphic: Global warming from 1880 to 2013”, http://climate.nasa.gov/climate_resources/28/ / NASA model researchers study Earth climate create models test assumptions theory hypothesis causes trajectory global warming research written 61 climate models different approach elements climate system ice oceans atmospheric chemistry computer model generated results graphic ModelE2 created NASA's Goddard Institute for Space Studies GISS climate projections ModelE2 500,000 lines of code run on a supercomputer NASA Center for Climate Simulation Greenbelt Maryland global research project GISS results international climate-science research initiative climate science Coupled Model Intercomparison Project Phase Five Phase-5 designed models replicate known climate history projections world’s temperature results Intergovernmental Panel on Climate Change experiments Phase-5 research tests Earth’s temperature atmospheric carbon dioxide world’s climate burning fossil fuels current rate experiments research groups reproduce climate from 1850-2005 climate factors forcings contribute contribution temperatures graphic GISS observed temperature data Phase-5 historical experiment temperatures climate scientists report climate results temperatures annual temperature departs from an average baseline departures anomalies temperature anomalies more consistent absolute temperatures absolute temperature several degrees absolute temperature differences averages temperature fewer monitoring stations measurement simulation results aligned observations 1880-1910 average temperatures trends shape trajectory line single year’s temperature observed line GISS global land ocean temperature record temperature lines modeled modelled modelling modeling estimates climate factor contributes overall temperature simulated different initial conditions average GISS researchers historical simulations modeled years Phase-5 historical experiment observed data confidence ranges researchers models reproduce weather events El Niño phases models whole system behaves El Niño equatorial Pacific Ocean warms simulation El Niño temperature lines average model’s estimates uncertainty bands outer range reasonable estimates temperature lines modeled results observations 95% simulations forcing data raw observational model data /