Greenhouse gas emissions

Greenhouse gas is a natural part of the atmosphere. It absorbs solar radiation and keeps the earth warm enough to support life. Human activities including burning fossil fuels for energy, land clearing and agriculture have increased the amount of greenhouse gas in the atmosphere.

This section explains greenhouse gas emissions and looks at where Victoria's greenhouse gases come from.

Greenhouse gases

Apart from water vapour, which is the most common greenhouse gas, there are six main greenhouse gases:

  • carbon dioxide
  • methane
  • nitrous oxide
  • hydrofluorocarbons
  • perfluorocarbons
  • sulphur hexafluoride.

The first three occur naturally in the atmosphere, while the last three are synthetic, and are either used in industry or created as a by-product of industrial processes.

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Carbon dioxide (CO2)

Increases of the main greenhouse gas - carbon dioxide (CO2) - stem from burning petrol, coal, oil and natural gas, and from some activities, such as clearing trees and other vegetation and ploughing the soil. 

CO2 is the main contributor to climate change, and accounts for about two thirds of greenhouse gases produced by human activities.

As part of the natural carbon cycle, plants remove CO2 from the atmosphere as part of photosynthesis while humans and other animals release carbon dioxide into the atmosphere by animals as they breathe. However, activities like burning fossil fuels and intensive ag

riculture, are increasing atmospheric concentrations beyond natural and historical limits.

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Methane (CH4)

Methane is not as abundant as CO2, but is 21 times more effective at trapping heat making it a very potent greenhouse gas. It is released when vegetation decomposes in oxygen-free environments (such as a fire or landfill), as well as from animals in digesting their food. 
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Nitrous oxide (N2O)

Nitrous oxide also occurs naturally in the environment, but human activities increase its atmospheric concentrations. Sources of nitrogen include fertiliser, legumes, organic matter in soil and manure. These emissions are greatest when soils are warm and waterlogged, and in those with high carbon and nitrate contents. One unit of nitrous oxide is equivalent to 310 units of carbon dioxide.

To make measuring and accounting of greenhouse gases easier , all greenhouse gases are converted to a common unit, called CO2 equivalent or CO2-e.

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New for 2013

Climate change impacts on snow in Victoria: A Centre for Australian Weather and Climate Research report