The Sources and Recent Trends of Greenhouse Gases

The sources and recent trends of these gases are detailed below:

Carbon dioxide (CO₂) is the primary greenhouse gas that is contributing to recent climate change. It is released through natural processes such as respiration and volcanic eruptions and through human activities such as deforestation, land use changes and burning fossil fuel. The United States Geological Survey reports that human activities now emit more 135 times as much CO₂ as volcanoes each year. Human activities currently release over 30 billion tons of CO₂ into the atmosphere every year.

Fossil fuel is a general term for buried combustible geologic deposit of organic materials, formed from decayed plants and animals that have been converted to crude oil, coal, natural gas or heavy oils by exposure to heat and pressure. In the earth crust over hundreds of millions of years.

Methane (CH₄) is a hydrocarbon gas produced both through natural sources and human activities, including the decomposition of waste in landfills, agriculture especially rice cultivation, as well as ruminant digestion and manure management associated with domestic livestock. For molecule basis, methane is far more active greenhouse gas than carbon dioxide but also one which is much less abundant.

Nitrous Oxide (N₂O) is a powerful greenhouse produced by soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production and biomass burning. Concentrations of N₂O have risen approximately 20% since the start of the industrial revolution with a relatively rapid increase towards the end of the 20th Century.

Water vapour is the most abundant greenhouse gas and also the most important in terms of its contribution to the natural greenhouse effect despite having a short atmospheric lifetime. It causes 36%-70% of the greenhouse effect. Some human activities can influence local water vapour levels.

However, on a global scale the concentration of water vapour is controlled by temperature which influences overall rate of evaporation and precipitation. Therefore the global concentration of water vapour is not substantially affected by direct human emissions.

Chlorofluorocarbons (CFCs), Hydro chlorofluorocarbons (HCFCs), Hydro fluorocarbons (HFCs), Per fluorocarbons (PFCs) and Sulfur hexaflouride (SF₆), together called F-gases are often used in coolants, foaming agents, fire extinguishers, solvents, pesticides and aerosol propellant. Unlike water vapour these F-gases have a long atmospheric lifetime and some of these emissions will affect the climate for many decades or centuries.