What are greenhouse gases (GHG)?
Greenhouse gases and the greenhouse effect
We can use the following everyday example to understand what greenhouse gases are about.
Greenhouse gases are a natural phenomenon that works like a garden greenhouse. Solar energy, in the form of light rays, arrives by going through the greenhouse glass. This energy is absorbed by plants, soil and all other objects contained in the greenhouse. A large part of this captured energy is converted into heat, which allows it to warm the greenhouse and maintain a pleasant temperature. The greenhouse glass helps keep the greenhouse warm by retaining heat.
Our planet's atmosphere acts like the glass of a greenhouse. Slightly over a third of solar light enters the atmosphere and the earth's surface (particularly snow and ice) and less than a third (about 20%) is absorbed by the atmosphere. The rest of the solar light is absorbed by Earth and oceans where it is converted into heat to warm the Earth and air.
Certain gases in particular, present in the atmosphere, act like greenhouse glass by preventing heat from escaping, these are greenhouse gases.
These greenhouse gases absorb light and send back a part to the Earth's surface, thereby raising temperatures.
Water vapour is the most important and active element in natural greenhouse gases. Nonetheless, other gases, even though they appear in small quantities, greatly and increasingly contribute to greenhouse gases; these include carbon dioxide, methane and nitrous oxide.
Without this greenhouse effect, the Earth would be colder than now by 33°c, for an average temperature of about -18°c.
The infamous carbon dioxide (CO²)
Carbon dioxide is a colourless, odourless non-inflammable and explosive gas.
We distinguish natural emissions from man-made emissions.
Natural emissions result from the living-cell activity of plants, animals and people. Therefore, CO² is produced by breathing or the decomposition of organic matter. Man-made emissions are those mainly caused by human activities such as industrial production, intensive farming or even the burning of fossil fuels during transportation.
Beyond the natural production of carbon dioxide, that attributable to human activity strongly contributes to global warming. Concentrations of CO² have greatly increased over the last decades, thereby accentuating climate change.