What are the Greenhouse Gases?

Almost every day, we hear about climate change and its impact on our environment caused by greenhouse gases. But what are greenhouse gases and are all greenhouse gases the same.

Let’s look at the most well-known greenhouse gas

Carbon Dioxide
The most abundant greenhouse gas is Carbon Dioxide (or sometimes call CO2 after its chemical structure of one Carbon atom and two Oxygen atoms).

Carbon Dioxide is formed when a carbon-based material, such as petrol, natural gas, coal and wood, is burnt.

The CO2 gas travels into our atmosphere and acts as a barrier to any heat escaping our planet. This is a positive natural mechanism as, without this barrier, the Earth would rapidly lose its heat and the planet would be much colder. However, too much CO2 will trap too much heat causing climate change and other impacts on our environment.

Concentrations of the Carbon Dioxide in our atmosphere have risen by around 40% since the Industrial Revolution. This means that atmospheric mixing ratios for CO2 are now over 400 parts per million (ppm) compared to pre‐industrial levels of 280 ppm.

So, CO2 is the main greenhouse gas and the benchmark for climate change impact with all other Greenhouse Gases benchmarked against CO2 as we will see later.

Methane gas (CH4) comes from both, natural and anthropogenic source. There are certain microbes that produce methane, as well as through geological processes. However, human factors include:

The burning of fossil fuels

Raising livestock, particularly cattle

Landfills and waste

Rice cultivation

The burning of biomass and biofuels

With reference to the Global Warming Potential, which is a measure of the interaction of a gas with the atmosphere, Methane has a Global Warming Potential relative to CO2, Methane is 25. That means 1 tonne of Methane is equivalent to 25 tonnes of CO2.

Concentrations of the Methane in our atmosphere have after a decline in the 1980s to 2000 and a period of a constant concentration between 2000 to 2006 started to increase to around 1,900 parts per billion. Indeed, methane concentrations are about 2.5 times as much as was in the atmosphere in the 1850s.

Nitrous oxide
Nitrous oxide (N2O) occurs naturally in the soil under vegetation and is produced when microbes break down nitrogen. Similarly, the oceans produce a significant amount of natural N2O during various processes. Human activities also result in nitrous oxide as a greenhouse gas:

The production and use of synthetic fertilisers, which increased the production of N2O in the soil

Agricultural runoff, where fertilisers and soil leach into water systems

The burning of fossil fuels and biomass

With reference to the Global Warming Potential of Nitrous oxide relative to CO2, Nitrous oxide is 298. That means 1 tonne of Nitrous oxide is equivalent to 298 tonnes of CO2.

Concentrations of the Nitrous oxide in our atmosphere have had a steady rise since the 1970s and, now, stands at nearly 335 parts per billion.

After the main Greenhouse Gases of Carbon dioxide, Methane and Nitrous oxide, there are four other less abundant but equally important Greenhouse gases.

Hydrofluorocarbons (or HFCs) are a family of man-made organic compounds that contain fluorine and hydrogen atoms with nineteen HFCs identified as Greenhouse Gases. These gases are frequently used in air conditioning and as refrigerants with R-134a, being one of the most commonly used HFC refrigerants.

Perfluorocarbons (PFCs) are man-made compounds containing just fluorine and carbon. Nine Perfluorocarbons are identified as Greenhouse gases. They are used in specialist applications, such as fluoropolymers, refrigerants, solvents, and anaesthetics.

Sulphur hexafluoride
Sulphur hexafluoride (SF6) is molecule consisting of six fluorine atoms attached to a central sulphur atom, and primarily used as an electrical insulator and arc suppressant.

Nitrogen trifluoride
Nitrogen trifluoride (NF3) is used to remove silicon and silicon-compounds and is increasingly within the manufacturing of flat-panel displays, photovoltaics, LEDs and other microelectronics.

NOAA Annual Greenhouse Gas Index
A neat way of summarising all the effects of the combined Greenhouse Gases that we have seen during this episode has been prepared by the United States National Oceanic and Atmosphere Administration (NOAA) in the form of an Annual Greenhouse Gas Index (or AGGI).

Taking all the current Greenhouse Gases into account within the NOAA Annual Greenhouse Gas Index (AGGI) & with the index set at 1 for the year 1990, as shown on the right axis provides clear evidence of the rise of the Greenhouse Gases over the past 30 years especially the rise of Carbon Dioxide in our atmosphere.

So, to summarise:

There are thirty-three Greenhouse Gases recognised by the United Nations Framework Convention on Climate Change (UNFCCC).

Some are man-made only & others are both, naturally occurring and man-made.

They vary in abundance from Carbon Dioxide to specialist chemicals used in manufacturing.

They vary in their greenhouse gas effect by the Global Warming Index.

All of them are increasing in our atmosphere and should be a cause for concern over their impact on climate change, now and into the future.

If hope that this article has helped to advance your understanding on Greenhouse Gases and how each gas can have a significant impact on climate change through their concentration in the atmosphere and their Global Warming Potentials, If this article has helped you or if you want to ask any questions about Greenhouse Gases, please leave a comment in the box below,

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