In the United States, the majority of human-caused (anthropogenic) greenhouse gas (GHG) emissions come from burning fossil fuels such as coal, natural gas, and oil for energy. The global emissions estimates outlined in the Fifth Assessment Report of the Intergovernmental Panel (IPCC) on Climate Change are slightly different than those found on the Sources of Greenhouse Gas Emissions page. For example, the IPCC energy supply sector for global emissions includes burning fossil fuels for heat and energy in all sectors, while the Sources of Greenhouse Gas Emissions page attributes on-site heat and energy emissions to their respective sectors. The production of electricity and heat is the largest contributor to global emissions, followed by transportation, manufacturing and construction, and agriculture.
It is essential for countries to understand where emission reductions could have the greatest impact by analyzing the breakdown of greenhouse gases by sector. Energy consumption is responsible for 75.6% (37.6 GtCO2e) of human-caused greenhouse gas emissions worldwide. Other sectors have seen an increase in emissions since 1990, including agriculture (12% increase), industrial emissions (180% increase), and waste (16% increase). Transport-related greenhouse gas emissions come mainly from passenger cars and light trucks, including SUVs, vans, and minivans.
Electricity-related emissions have decreased by 21% since 1990 due to a shift in generation to lower-emission sources and an increase in end-use energy efficiency. Other sources of energy-related emissions include energy production from other fuels, on-site heat sources, combined heat and power (CHP), nuclear industry, and pumped hydroelectric storage. Globally, the main sources of greenhouse gas emissions are electricity and heat (31%), agriculture (11%), transport (15%), forestry (6%), and manufacturing (12%). China is one of the largest importers of oil, contributing to large CO2 emissions through motor vehicles in the country.