What is the greenhouse effect?
“Greenhouse gases” are essential to maintaining the right temperature on our planet for life. Without the natural greenhouse effect, the heat that the Earth emits would simply escape through its surface and into space, resulting in an average temperature of -20 °C.
Natural greenhouse gases are a component of our atmosphere. Since of this, Earth is sometimes referred to as the “Goldilocks” planet because its climate is just suitable for life to thrive, including humankind. The Earth’s built-in greenhouse effect, which typically keeps the globe at a comfortable 15 °C (59 °F), contributes to why it is so hospitable.
However, for the past century or two, people have been affecting the energy balance of the planet, primarily by burning fossil fuels, which increases the amount of carbon dioxide in the atmosphere. For decades, the amount of carbon dioxide in the Earth’s atmosphere has been steadily increasing, which traps more heat close to the surface and raises temperatures.
The reason a gas is called a greenhouse is because it absorbs heat from the sun’s infrared radiation, which is then circulated throughout the atmosphere before being lost to space. Although it has a considerably smaller impact on global temperatures, greenhouse gases also speed up the atmosphere’s ability to absorb solar short-wave radiation.
More heat from the sun is being trapped in our atmosphere thanks to the accumulation of CO2 produced when fossil fuels are burned. The term “anthropogenic” refers to human-made behaviours, and the release of CO2 is one such action that contributes to the current enhanced greenhouse effect.
Which gases cause the greenhouse effect?
A greenhouse gas’s contribution to the greenhouse effect is determined by how much heat it absorbs, how much it radiates back, and how much of it is present in the atmosphere.
The gases that contribute most to the greenhouse effect on Earth are, in descending order:
- liquid vapour (H2O)
- Oxygenated air (CO2
- Noxious gas (N2O)
- methane (CH4)
- ozone (O3)
CH4 is 23 times more effective than CO2 in terms of the amount of heat it can absorb and reradiate (also referred to as its global warming potential, or GWP). N2O is 296 times more effective than CO2. The atmosphere of the Earth contains significantly more CO2 than CH4 or N2O, though.
Not all of the greenhouse gases we release into the atmosphere linger there permanently.
This is because air and water mix efficiently at the sea surface, for instance, the amount of CO2 in the atmosphere and the amount of CO2 dissolved in the surface waters remain in balance. The amount of CO2 that dissolves into the oceans increases as we increase the amount of CO2 in the atmosphere.
Related: How do Trees impact our Environment?
Greenhouse gases that are Anthropogenic
Human-caused activities have significantly raised greenhouse gas concentrations in the atmosphere since the Industrial Revolution began in the middle of the 18th century. Since pre-industrial levels were far lower, observed atmospheric CO2 amounts are now significantly greater.
Overview of global anthropogenic greenhouse gas emissions in 2017; figures here are expressed in CO2-equivalents. Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2015 (EPA, 2017).
The main sources of anthropogenic greenhouse gases
Fossil fuels are burned
Since the previous 750,000 years, carbon dioxide levels have increased significantly. Fossil fuel combustion has caused CO2 levels to increase from a pre-industrial atmospheric concentration of about 280 parts per million (ppm) to above 400 ppm in 2018. Since the beginning of the Industrial Revolution, this has increased by 40%.
By the end of the twenty-first century, CO2 levels are anticipated to exceed 900 ppm and are rising at a pace of roughly 2-3 ppm/year.
By 2100, the average global surface temperature may have risen up to 4.8°C over pre-industrial levels if this trend persists along with rising emissions of CH4 and other greenhouse gases.
Forestry, agriculture, and other land uses
One-fourth of net human greenhouse gas emissions are caused by changes in land use, including agriculture, deforestation, and other activities. A United Nations research estimates that 14.5 percent of this is caused by animals.
The principal emitting factors are:
1. Production and processing of feed (45 per cent)
2. Greenhouse gas emissions from cows’ digesting (39 per cent)
3. Decomposition of manure (10%)
The transportation and processing of animal products are responsible for the remaining costs.
Agriculture is estimated to be the main driver for around 80 per cent of deforestation worldwide. Source: Pixabay.
Production of Cement
When calcium carbonate is heated, lime and CO2 are produced, which is a byproduct of cement production.
It is generally agreed that the cement industry contributes between five and eight percent of the world’s anthropogenic CO2 emissions, of which fifty percent are due to the chemical process itself and forty percent are attributable to the use of fuel to power that process. Every time 1000 kg of cement are produced, the cement industry emits more than 900 kg of CO2.
A cement works in Clitheroe. The cement industry produces around five per cent of global anthropogenic CO2 emissions. © Alan Murray-Rust.
When humans burn fossil fuels, tiny particles that are floating in the atmosphere can become aerosols. Chlorofluorocarbons (CFCs) used in refrigeration systems, CFCs and halons used in fire suppression systems, and pollution from factories and autos are some other anthropogenic sources of aerosols.
A variety of natural activities, such as forest fires, volcanic eruptions, and the release of isoprene from plants, can also result in the production of aerosols. Although it is well known that greenhouse gases warm the surface of the Earth, aerosol pollution in the air can have the opposite effect. For instance, sulphate aerosols produced by the burning of fossil fuels chill the planet by limiting the quantity of sunlight that reaches the planet.
The scattering of radiation causes atmospheric cooling, whereas absorption can cause atmospheric warming. Source: © Taro Tayler.
The Earth would be roughly – 17 degrees without “greenhouse gases,” which are actually essential to keeping our planet at a temperature that is habitable. An increased or new greenhouse effect is being caused by anthropogenic, or human-induced, carbon dioxide emissions.
It is demonstrated that all IR radiation inside each of their individual spectral bands originates at the surface and is reflected back to it by the greenhouse gases carbon dioxide and water vapour. The thickness of this layer, which contains this reflection, is just 12 cm at the surface.