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Greenhouse gases

We hear about greenhouse gases all the time, but CO2 is not the only one.

Earth

Credit: Wikimedia

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What is it?

Greenhouse gases (GHG) are the gaseous parts of our atmosphere that contribute to the greenhouse effect - a phenomenon that causes the Earth's atmosphere to heat up.

There are seven main gases. Water vapour is actually the most common GHG; others include the well-reported carbon dioxide (CO2), methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride.

Some of these occur naturally as part of our ecosystem, some are manmade and some are naturally occurring but increased by human behaviour (like CO2).

The main job of greenhouse gases is to maintain the Earth's temperature, which is a good thing. They help to trap some energy from the sun and keep it in our atmosphere. Without greenhouse gases humans would freeze.

So why are GHG's bad?

As the sun's rays pass through our atmosphere on the way in, the solar radiation warms the Earth. After it hits the Earth's surface, some of it is reflected back towards the atmosphere as infrared energy.

It's there that greenhouse gas come into action by acting as a blanket, keeping some of the infrared within the atmosphere (but still allowing some to escape). This process is known as the greenhouse effect.

The problem arises when we have an abundance of greenhouse gas and too much infrared is retained and not enough is allowed to escape. There's an imbalance in the greenhouse effect, which causes global warming.

Which ones are the worst?
  • Carbon dioxide
    CO2 is produced by plants and animals but human activities, such as burning fossil fuels for electricity and transportation and clearing land for agriculture, increase CO2 levels beyond the natural capabilities of the atmosphere. CO2 is a greenhouse that is produced in large quantities by humans, which is why we're encouraged to concentrate more on reducing our carbon emissions more than other greenhouse gases.
  • Methane
    Methane is much more potent greenhouse gas than CO2 (25 times more) but is present and produced, in far smaller quantities. It is produced by waste in landfill (because it breaks down without the presence of oxygen) and digestive functions of animals.
  • Nitrous oxide
    Known as NO, it occurs both naturally and from human-related sources. It's mostly emitted when chemical fertilisers or manure is used in agriculture, though is also released in the combustion of fossil fuels.
How can we reduce GHG's?

By reducing our reliance on fossil fuels, reducing waste, reusing and recycling we can reduce our emissions of major greenhouse gases.