While a wide range of natural phenomena can radically affect the climate, global warming and resultant climate effects that we’re witnessing are the result of human activity.
Life on Earth is dependent on an atmospheric “greenhouse” – a layer of gasses, primarily water vapour, in the lower atmosphere that trap heat from the sun as it’s reflected back from the Earth, radiating it back and keeping our planet at a temperature capable of supporting life.
Human activity is currently generating and excess of long-lived greenhouse gasses that – unlike water vapour – don’t dissipate in response to temperature increases, resulting in a continuing build up of heat.
Key greenhouse gasses include carbon dioxide, methane and nitrous oxide. Carbon dioxide is the best-known, with natural sources including decomposition and animal respiration. The main source of excess carbon dioxide emissions is the burning of fossil fuels, while deforestation has reduced the amount of plant life available to turn CO2 into oxygen.
Methane, a more potent but less abundant greenhouse gas, enters the atmosphere from farming – both from animals such as cattle and arable farming methods including traditional rice paddies – and from fossil fuel exploration and abandoned oil and gas wells.
Chlorofluorocarbons and hydroflurocarbons– once widely used in industrial applications and home appliances such as refrigerators – were key greenhouse gasses released during the 20th century, but are now heavily regulated due to their severe impact on the atmosphere, which includes ozone depletion, as well as trapping heat in the lower atmosphere.
Our warming climate is also creating a feedback loop as greenhouse gasses trapped in Arctic permafrost are released.