So what exactly are greenhouse gases?

WE flippantly and so glibly use the word ‘climate change’ to explain why our climate is getting forever warmer or if we have a prolonged period of rain of an unseasonal character.

What we tend to forget is the very reason for a rise in the world’s average temperature. Simply the cause of climate change and global warming mainly lies in the dramatic increase of GHGs in our atmosphere.

GHGs are greenhouse gases, composed of any gaseous compounds, in the air we breathe and higher in the atmosphere, that are capable of absorbing infrared radiation from the sun, thus trapping and holding heat in the atmosphere. This greenhouse effect is the result of an increase in heat in the lower atmosphere, which leads to global warming.

This not a relatively new discovery as we are often led to believe. It was first recorded by the Swedish Nobel-Prize winning physical chemist Svante Arrhenius in the London published ‘Philosophical Magazine and Journal of Science’ in 1896. He highlighted the contribution of carbon dioxide (CO2) to the greenhouse effect. This was once known as the Arrhenius effect.

Arrhenius referred to carbon dioxide as carbonic acid. Interestingly in the 1960s, acid rain (dilute carbonic acid) was cited as the cause of death of many species of pine trees in Scandinavia.

The countries blamed then for the death of these trees were Germany and the United Kingdom, the then industrial power houses of European manufacturing industries.

Approximately 30 per cent of solar radiation approaching the Earth is reflected back into space by clouds, ice and other reflective surfaces such as sand deserts and beaches. The remaining 70 per cent is absorbed by the atmosphere, land surface and the ocean.

The difference between the percentage of incoming and outgoing radiation maintains the overall average temperature of our planet at approximately 15 degrees centigrade.

Which gases are classified as GHGs?

The major GHGs are water vapour (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Oxygen, however, does not absorb infrared radiation. The Industrial Revolution (starting around 1750 AD) and subsequent industrial developments have had a major part to play in the amount of atmospheric carbon dioxide we experience today.

During the Ice Ages, calculated through deep ice-cap core drillings, the amount of CO2 in our atmosphere fluctuated between 180 parts per million (ppm) and 220 ppm.

Ice is a natural absorber of CO2, so during the great melt of the continental glaciers and ice caps at the end of the Ice Ages (11,000 years ago), huge quantities of stored CO2 were released back into the atmosphere. With global warming and the gradual but increasing melt of the Arctic Ocean and the thinning of the Greenland and Antarctic ice-caps, more CO2 is given back into the atmosphere.

Despite this natural release of CO2, it has been calculated that since the Industrial Revolution the amount of CO2 has rapidly increased to 100 times faster than when the last Ice Age finished.

Viewed on a more recent time scale, human activities such as the combustion of fossil fuels, deforestation (trees are massive carbon stores) soil erosion, and animal rearing – all referred to as anthropogenic carbon dioxide emissions – have increased since 1750 at 280 ppm to 406 ppm this year.

Other GHGs

Ozone (O3) is yet another absorber of heat as are fluorinated gases and chlorofluorocarbons (CFCs). The former, containing the element fluorine, is created by industrial processes.

Whilst present in small concentrations, these gases are very effective at trapping heat resulting in high global warming potential (GWP) gases. CFCs were once used as refrigerants and aerosol propellants but, recently, have been phased out by international agreements.

Methane – the deep coal miners’ scourge – in the form of inflammable ‘coal gas’ is also emitted from peat bogs and from the thawing permafrost of today’s tundra-lands.

It is also derived from flatulence amongst cattle herds and produced in the complex digestive system as cattle chew the cud, together with a particular bacterium living in their stomachs. Cattle manure collection and slurry creation to feed onto farmers’ fields, including paddy fields, also add vast quantities to the atmosphere.

With a shorter life span of 12 years compared to CO2 (30 to 95 years), nitrous oxide (114 years) and CFCs (100 years), methane does however have a 72 times stronger absorption of heat than carbon dioxide.

GHG sinks

CO2 is naturally removed from the atmosphere, not only by increased glaciation, as in the Ice Ages, and in permafrost areas but also in its absorption into our oceans as well, through the process of photosynthesis in our forests, our plants and our soils.

Deforestation removes this collection sink but replanting helps restore the lost sink. It is calculated that more than 50 per cent of all CO2 emitted is removed from the atmosphere within a century. However, 20 per cent remains in the atmosphere for thousands of years.

Earth’s surface temperatures

If GHG emissions continue at the present rate, our annual mean surface temperatures could well continue to exceed historical values. This will have disastrous effects on our ecosystems, biodiversity, and the livelihoods of people worldwide.

We have already witnessed obvious temperature rises in our oceans as seen in coral bleaching in Sabah and Sarawak, and the lowering of fish stocks near such coral reefs.

The United Nations International Panel on Climate Change (IPCC) has brought all nations, apart from a very few, to account for and tried to reduce gaseous emissions.

Interestingly, the UK recently declared that for the first time ever its electricity generation was provided without coal-fired power stations. As it is summertime in the UK, when domestic demands for electricity fall, let’s wait until next winter to see if this is maintained.

There is no doubt that all countries must reduce their current anthropogenic gaseous emissions by 2036 to avoid passing the danger limit of 2 degrees centigrade global warming.

Last year was the warmest year on record, with 11 of the hottest years since 1998. Unless we reduce our gaseous emissions, changes will occur in rainfall distributions with more frequent droughts and, indeed, flooding as recently seen in Quebec, Canada. Flooding in some parts of the globe will no longer be seen as a hundred-year disaster but every other year.

Extreme weather, rising sea levels, the extinction of flora and fauna, acidification of our oceans, and increases yet of more human migrants may see the Reverend Thomas Robert Malthus’s proclamation, in his 1798 work entitled ‘An Essay on the Principle of Population’, essentially outlining natural population controls become a distinct reality.

This is a very frightening thought and gives us all much to eschew.