Greenhouse gases and the greenhouse effect
Greenhouses gases and the 'greenhouse effect' are an essential part of the balance which creates the Earth's unique atmosphere within our solar system.
While other planets such as Venus have scorching temperatures, or freeze - like Neptune - Earth's temperatures are largely temperate. This is due to our atmosphere, the thin layer of gases cloaking our planet, and the distance of the Earth's orbit from the sun.
This balance, which warms Earth but prevents it from becoming too warm, is often referred to as the 'greenhouse effect'1 - because it works much like a greenhouse.
Solar radiation from the sun constantly strikes the Earth's atmosphere, mostly in the form of visible, ultraviolet and infrared light. About 30 per cent of this is reflected immediately back out to space while the rest is absorbed by oceans, land and atmosphere then released as infrared thermal radiation (or heat), passing out of the atmosphere and into space.
Carbon dioxide 2 (CO2) has always been part of this delicate balance, trapping heat in the atmosphere. For hundreds of thousands of years, the concentrations stayed between 200 and 300 parts per million. However, since the industrial revolution 3, humans have burned huge amounts of fossil fuels - such as coal, oil and petrol. These contain carbon, and when they are burnt this combines with oxygen to form CO2.
This, alongside other human activities, from farming to deforestation, has greatly increased concentrations of greenhouse gases, particularly CO2, disrupting that atmospheric balance. There is estimated to be at least 30 per cent more CO2 in our atmosphere than 150 years ago.
These greenhouse gaseous compounds absorb infrared radiation - trapping and holding heat in the atmosphere, ultimately leading to global warming.
As well as fossil fuels, other activities contribute to increased greenhouse gases.
The United States Environmental Protection Agency (USEPA 4), cites the key greenhouse gases emitted by human activities, as:
- CO2 - from fossil fuels such as coal and from deforestation
- Methane - through agricultural activities, waste management, energy use and burning of biomass - like wood
- Fluorinated gases - industrial processes, refrigeration, and use of a variety of consumer products contribute to emissions of F-gases, which include hydrofluorocarbons, perfluorocarbons, and sulphur hexafluoride (SF6)
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It's almost universally acknowledged that if greenhouse gas emissions continue unchecked, it will cause climate change, rising sea levels and extreme weather events. In response, there is an international movement via the UN to try to mitigate impacts through policies that reduce the atmospheric concentrations of greenhouse gases.