Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (CO2), from burning fossil fuels such as coal, oil, and natural gas, is the main cause of climate change. The largest annual emissions are from China followed by the United States. The United States has higher emissions per capita. The main producers fueling the emissions globally are large oil and gas companies. Emissions from human activities have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but have been consistent among all greenhouse gases. Emissions in the 2010s averaged 56 billion tons a year, higher than any decade before. Total cumulative emissions from 1870 to 2022 were 703 GtC (2575 GtCO2), of which 484±20 GtC (1773±73 GtCO2) from fossil fuels and industry, and 219±60 GtC (802±220 GtCO2) from land use change. Land-use change, such as deforestation, caused about 31% of cumulative emissions over 1870–2022, coal 32%, oil 24%, and gas 10%.
Carbon dioxide is the main greenhouse gas resulting from human activities. It accounts for more than half of warming. Methane (CH4) emissions have almost the same short-term impact. Nitrous oxide (N2O) and fluorinated gases (F-gases) play a lesser role in comparison. Emissions of carbon dioxide, methane and nitrous oxide in 2023 were all higher than ever before.
