Greenhouse gases, GHG, are part of the greenhouse effect. The latter is the process that keeps the Earth warm. The most important greenhouse gas is CO2 (carbon dioxide). Other examples are methane, nitrous oxide and water vapour. All these gases can absorb heat.
In other words, greenhouse gases trap heat from the sun, which is a natural part of the greenhouse effect and leads to a warmer climate. However, too many greenhouse gases in the atmosphere lead to higher temperatures than life on Earth is used to. The abundance of GHG is the leading cause of climate change. Human activities, such as industries, agriculture and the global transport system, release large amounts of greenhouse gases.
Global Warming Potential
Some greenhouse gases are better at absorbing the sun’s heat than others. The Global Potential, GWP, is a scale showing this difference. It is based on how well carbon dioxide (CO2) absorbs heat. Then it compares it with other gases. Read more below for an example.
The GWP has three factors. First, how efficiently the gas absorbs the sun’s heat. Second, the amount of time that the gas stays in the atmosphere. For example, about 15-40 % of emitted CO2 stays for more than 1000 years. The third factor is a bit more complicated to understand. It is related to something called the infrared wavelength range. In short, some gases absorb heat where the atmosphere’s ability to capture heat is already high. This factor can lead to a lower GWP because the gas cannot absorb much heat there.
For example, nitrous oxide has a GWP of around 300. This number means that 1 kg of nitrous oxide emissions is just as good as absorbing heat as 300 kg of CO2. In other words, nitrous oxide absorbs much more heat than CO2. Read more on this under the headline “nitrous oxide”.
Greenhouse gas – Carbon Dioxide
Carbon dioxide, CO2, is the primary greenhouse gas emitted by human activities. It also gets released through the breathing of humans, animals and plants. As long as organisms on the Earth live and die, the level of CO2 in the air is balanced. However, this natural balance is disturbed by human activities. For example, the burning of fossil fuels emits enormous amounts of CO2. Driving and flying are also significant sources of CO2 emissions. These emissions all help to trap the sun’s heat in the air, which leads to global warming.
There are many ways to reduce the increase of CO2, such as working to lower the emissions. For example, by stopping the use of fossil fuels. Or attempting to bind CO2 naturally by restoring forests or planting trees. More so, there are technologies that capture and store CO2, known as “Carbon Capture and Storage – CCS”.
Greenhouse gas – Nitrous Oxide
Nitrous Oxide (N2O) is another common greenhouse gas. It is also known as laughing gas. For example, N2O is used in medical and dental procedures as it has soothing qualities and can help patients relax. As mentioned above, nitrous oxide has a GWP factor of around 300 compared to carbon dioxide. This number means that it is 300 times more potent than carbon dioxide. In other words, it is 300 times better at absorbing the sun’s heat and contributing to a warmer climate. Fortunately, nitrous oxide gets emitted in much smaller quantities than carbon dioxide.
Greenhouse gas – Methane
Methane(CH4) has a GWP of 25. Meaning it has a 25 times stronger impact on the climate than the same amount of CO2. However, methane stays in the atmosphere for a shorter amount of time. A large part of the emissions of methane comes from agriculture. It gets emitted through the production of meat and dairy products. More so, methane gets stored in tiny bubbles in glaciers. It gets released with global warming as the ice melts. The process creates a so-called feedback effect; when the melting ice releases methane, it contributes to the even faster melting of the ice.
Other greenhouse gases
Water vapour is also a greenhouse gas. It is responsible for about 2/3 of the natural greenhouse effect in the atmosphere.