What are greenhouse gases?
Greenhouse gases are coming from natural and anthropogenic origin (linked to human activity) that absorb and emit part of the sun's rays. This is a thermal phenomenon called the greenhouse effect.
In agriculture, a greenhouse is used to heat the temperature of agricultural crops. On Earth, the atmosphere has the same function as a greenhouse and greenhouse gases contribute to global warming. Without the greenhouse effect, the Earth's temperature would be around -18°C. This is an important and useful phenomenon for life on Earth. However, the atmosphere is fragile and excess greenhouse gases upset the balance by contributing to global warming.
What are they?
According to the IPCC (Intergovernmental Panel on Climate Change), some 40 gases have been identified in the atmosphere. The atmosphere is made up of many gases such as nitrogen (78%), oxygen (21%) and rare gases (1%) such as ozone (O3) and carbon dioxide (CO2).
However, in the atmosphere, greenhouse gases absorb and emit part of the sun's rays. The greenhouse gases that are naturally present in the majority are :
- Water vapour (H2O)
- Carbon dioxide (CO2)
- Methane (CH4)
- Ozone (O3)
- Nitrous oxide (N2O)
Greenhouse gases only related to human activity from industry are also present in our atmosphere, called halocarbons.
Where do they come from?
Despite the natural presence of some of these gases, human activity plays an important role in their concentration in the atmosphere. Indeed, it is constantly increasing and causing an increase in the Earth's global temperature. This is known as global warming.
The concentration of naturally occurring greenhouse gases in the atmosphere is increased by human activity, in particular :
- Carbon dioxide (CO2) is the main greenhouse gas emitted by humans and accounts for 77% of emissions according to the Ministry of Ecological Transition, i.e. an emission of approximately 10 Gt per year. (Global Budget 2020)
This gas comes mainly from the combustion of fossil fuels (transport, industry, food industry, etc.) and has a lifetime in the atmosphere of about 100 years.
- Methane (CH4) comes mainly from the agricultural sector, landfills, coal, oil and gas operations and has a lifetime of about 12 years in the atmosphere. Methane accounts for more than 15% of anthropogenic greenhouse gases. According to the IPCC, the global warming capacity of methane is twice that of CO2. In addition, the chemical reactions of methane produce carbon dioxide (CO2), ozone (O3) and water vapour (H2O).
- Nitrous oxide (N20) accounts for about 5% of emissions. This gas comes mainly from the use of fertilisers in agriculture and from some chemical processes.
Since the industrial era (before 1750), three new anthropogenic gases have contributed to the greenhouse effect:
- Hydrofluorocarbons (HFCs)
- Perfluorocarbons (PFCs)
- Sulphur hexafluoride (SF6)
Halocarbons account for about 10% of the greenhouse effect and come mainly from refrigeration and air conditioning systems and the chemical industry. Moreover, these gases have a very long lifetime in the atmosphere, up to 50,000 years.
Before these gases dissipate into the atmosphere and disappear completely, a huge amount of time passes on a human scale and every gas emission released by human activity still contributes to climate change.
This graph from Our World in Data shows the distribution of greenhouse gases by sector in 2016. The energy sector is the largest emitter of greenhouse gases at 73.2%, followed by agriculture at 18.4%, industry at 5.2% and waste at 3.2%. The IPCC annual report continuously indicates an increase in concentrations, especially of CO2 corresponding to ⅔ of greenhouse gas emissions in the atmosphere.
The build-up of greenhouse gases in the atmosphere has been going on for many years and historically the US has led the way with over 509 Gt of CO2 released since 1850, or around 20% of total emissions according to Carbon Brief analysis. China accounts for 11%, Russia 7%, Brazil 5% and Indonesia 4%. For more information on the countries historically responsible for the increase in greenhouse gases, Carbon Brief offers an explanatory video: https://youtu.be/6zP0L69ielU .
Why and how to reduce greenhouse gases?
It is necessary to reduce greenhouse gases in order to combat climate change. Indeed, the increase of greenhouse gases disturbs the Earth's thermal balance and induces climate change. Climate change has many consequences for humans and the environment.
The direct and indirect consequences on people and the environment will be :
- Rising maximum temperatures, for example from one heatwave to ten every 15 years.
- Rising sea levels caused by melting glaciers.
- The melting of permafrost with the release of viruses that have been dormant for years.
- Loss of terrestrial and marine biodiversity due to climate change
- Economic consequences for the deployment of technologies to reduce greenhouse gases.
- Consequences for society with health risks, food crises and population movement…
Without changes, we will reach a non-return point. That is why it is essential to find solutions to fight against the consequences of climate change.
CO2 is the most emitted greenhouse gas by humans, so there is an option for us to reduce our carbon footprint and help reduce greenhouse gases.
Everyday actions taken by each individual can contribute to a small reduction in carbon footprint. However, as Times For The Planet says, peeing in the shower will not be enough.
More effective and drastic methods are being proposed by scientists who aim to deploy new technologies. For instance, negative emission technologies remove the majority of carbon dioxide (CO2) in the atmosphere. The aim is to capture and store CO2 on land, in the subsoil or in the oceans. However, technologies to remove carbon dioxide are not an alternative to climate change but a necessity.
Companies are taking action to combat climate change and reduce greenhouse gases. For example, Time for the Planet funds various climate projects such as the Leviathan Dynamics project, which presents an air conditioning system that uses water as a cooling fluid and does not emit greenhouse gases. Or Carbon Impact, which proposes to install finely ground olivine (a mineral derived from volcanic rock) at the edge of the ocean in order to use the energy of the waves and currents to accelerate one of the natural phenomena of CO2 capture.
