Greenhouse gas emissions
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 one of the most important factors in causing climate change. The largest emitters are 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.[2] Total cumulative emissions from 1870 to 2017 were 425±20 GtC (1558 GtCO2) from fossil fuels and industry, and 180±60 GtC (660 GtCO2) from land use change. Land-use change, such as deforestation, caused about 31% of cumulative emissions over 1870–2017, coal 32%, oil 25%, and gas 10%.[3]
Carbon dioxide (CO2) 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.[4] 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.[5]
Electricity generation, heat and transport are major emitters; overall energy is responsible for around 73% of emissions.[6] Deforestation and other changes in land use also emit carbon dioxide and methane. The largest source of anthropogenic methane emissions is agriculture, closely followed by gas venting and fugitive emissions from the fossil-fuel industry. The largest agricultural methane source is livestock. Agricultural soils emit nitrous oxide partly due to fertilizers. Similarly, fluorinated gases from refrigerants play an outsized role in total human emissions.
The current CO2-equivalent emission rates averaging 6.6 tonnes per person per year,[7] are well over twice the estimated rate 2.3 tons[8][9] required to stay within the 2030 Paris Agreement increase of 1.5 °C (2.7 °F) over pre-industrial levels.[10] Annual per capita emissions in the industrialized countries are typically as much as ten times the average in developing countries.[11]
The carbon footprint (or greenhouse gas footprint) serves as an indicator to compare the amount of greenhouse gases emitted over the entire life cycle from the production of a good or service along the supply chain to its final consumption.[12][13] Carbon accounting (or greenhouse gas accounting) is a framework of methods to measure and track how much greenhouse gas an organization emits.[14]
Global Energy-Related CO2 Emissions Report[edit]
In March 2024, the International Energy Agency (IEA) reported that in 2023, global CO2 emissions from energy sources increased by 1.1%, rising by 410 million tonnes to a record 37.4 billion tonnes, primarily due to coal. Drought-related decreases in hydropower contributed to a 170 million tonne rise in emissions, which would have otherwise led to a decrease in the electricity sector's emissions. The implementation of clean energy technologies like solar, wind, nuclear, heat pumps, and electric vehicles since 2019 has significantly tempered emissions growth, which would have been threefold without these technologies. The past decade has seen the slowest average annual growth in emissions since the Great Depression, at just over 0.5%. Advanced economies' emissions fell by 4.5% in 2023, despite a 1.7% GDP growth, reaching levels last seen fifty years ago. China experienced the largest increase in emissions at approximately 565 million tonnes, exacerbated by a historic decrease in hydropower, pushing its per capita emissions 15% higher than those in advanced economies. In India, emissions increased by 190 million tonnes due to strong GDP growth and reduced hydroelectricity production following a weak monsoon, with its per capita emissions remaining significantly below the global average.[251]