Some key sources of extra greenhouse gases entering the atmosphere include:
- Burning fossil fuels such as coal, oil, and natural gas for electricity production, transportation, and industry. This is the largest contributor, responsible for a significant portion of carbon dioxide (CO2) emissions
- Deforestation and land use changes , which release CO2 stored in trees and soil, accounting for about a quarter of total anthropogenic greenhouse gas emissions
- Agriculture , including livestock (especially cattle) which produce methane (CH4) during digestion, rice paddies that emit methane through anaerobic decomposition, and agricultural soils that emit nitrous oxide (N2O) due to fertilizer application
- Waste management , such as landfills and wastewater treatment, which generate methane as organic waste decomposes anaerobically
- Industrial processes , including cement production and certain chemical reactions, which emit CO2 and other greenhouse gases
- Fossil fuel extraction and processing , which cause methane leaks and venting from coal mining, oil and gas production, and pipelines
- Use of synthetic greenhouse gases like chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) in refrigeration, fire suppression, and manufacturing
Natural sources such as respiration, decomposition, and ocean release also emit greenhouse gases, but the recent rapid increase is primarily due to human activities
. In summary, extra greenhouse gases primarily come from fossil fuel combustion, deforestation, agriculture (especially livestock and rice farming), waste decomposition, industrial processes, and synthetic gases used in various technologies. These human-driven sources have significantly increased atmospheric greenhouse gas concentrations since the industrial era
