What is the greenhouse effect?

When greenhouse gases such as carbon dioxide build in the atmosphere, they act like a blanket around the earth. When sunlight (mostly short-wave radiation) hits this blanket, it passes straight through and continues until it reaches the surface of the planet.

The earth then absorbs this sunlight and emits a different type of light, longer-wave infrared radiation, back out to space. As it leaves the atmosphere, the infrared radiation also hits the greenhouse gas blanket. Most of it goes straight through, but some of it is absorbed and goes back down to earth.

This traps the infrared radiation and causes the surface to heat – a process we call the ‘greenhouse effect’.

Why greenhouse effect is important?

It is crucial to understand that the greenhouse effect is critical to life on earth. Without a blanket of greenhouse gases trapping in heat, the temperature would be bitterly cold, and humans would be unable to survive.

If greenhouse effect is important for survival then why it has become problematic?

Actually, by adding extra greenhouse gases into the atmosphere, humans have created an enhanced greenhouse effect.

The greenhouse gas blanket is now thicker and is absorbing more infrared radiation than before.

In other words, the greenhouse effect is stronger and, instead of keeping the earth at a stable temperature, it is causing the planet to heat up.

Give examples of natural greenhouse gases (GHGs).

Carbon dioxide (CO2)

CO2 is released through natural processes, such as volcanic eruptions, plant respiration and animals and humans breathing.

But the atmospheric CO2 concentration has increased by 50% since the Industrial Revolution began in the 1800s, due to human activities like the burning of fossil fuels and large-scale deforestation.

Due to its abundance, CO2 is the main contributor to climate change.

Methane

Methane is produced naturally through decomposition. But again, human activity has displaced the natural balance.

Large amounts of methane are released by cattle farming, landfill waste dumps, rice farming and the traditional production of oil and gas.

Nitrous oxide

Nitrous oxide is produced through the large-scale use of commercial and organic fertilisers, fossil-fuel combustion, nitric-acid production and biomass burning.

Water vapour

Water vapour is the most abundant greenhouse gas. It increases as the earth’s atmosphere warms but unlike CO2, which can remain in the earth’s atmosphere for centuries, water vapour persists for a few days.

The group of gases detailed above are naturally produced, but their increasing atmospheric concentration is man-made.

Give examples of man-made greenhouse gases (GHGs).

The three industrial fluorinated gases – hydrofluorocarbons (HFC), perfluorocarbons (PFC) and sulphur hexafluoride (SF6) – are solely man-made during industrial processes and do not occur in nature.

Though they are present in very small concentrations in the atmosphere, they trap heat very effectively, meaning they are extremely potent.

SF6, which is used in high-voltage electricity equipment, has a ‘Global Warming Potential’ 23,000 times greater than CO2.

What are the sources of greenhouse gases?

The biggest emissions come from electricity and heat production (25%), agriculture, forestry and other land use (24%), industry (21%), and transport (14%) –

One-quarter of human-made greenhouse gas emissions come from burning fossil fuels for electricity and heat production.

Another quarter of human-made greenhouse gas emissions come from Agriculture, Forestry, and Other Land Use (AFOLU).

To feed our livestock and ourselves, people have chopped down large areas of the forest and used the land to grow crops. Forests are very good at removing carbon dioxide from the atmosphere, and so cutting down trees allows carbon dioxide to build up in the atmosphere even more.

Land can also be used to rear livestock, such as cattle for meat and milk. These animals produce additional gases, like methane. They also eat crops that might otherwise have been needed by humans, meaning that even more land is required.

As well as fossil fuels, deforestation and land use, aeroplanes and the production of cement also contribute to emissions of carbon dioxide.

What can be done to reduce greenhouse gases?

Greenhouse gases can be reduced by phasing out fossil fuels, such as coal, oil and gas, and moving to renewable energy, such as solar and wind.

We can all play a part in protecting our planet, from simple daily changes, like reusing and recycling, to bigger lifestyle decisions like switching to electric vehicles.