Greenhouse gas emissions refer to the release of heat-trapping gases into the atmosphere – the so-called ‘greenhouse effect’ – thus causing global warming.
Interesting notes about greenhouse gas emissions
- Too much is too much. These gases are naturally present in the atmosphere and if they weren’t, the average global temperature would be as much as 33°C lower. The problem is the unprecedented accumulation of these emissions produced by human activities, which unbalances the normal functioning of the climate;
- A diverse group. CO2 is undoubtedly the best known greenhouse gas, but there are other gases that have impact the earth’s temperature albeit with different warming capacity and on a different time scales;
- A stock problem. An important note to keep in mind when discussing climate change mitigation and adaptation is that we are facing a stock problem and not a flux problem. Emissions accumulate in the atmosphere over several decades, depending on the specific gas, and this implies the need to think beyond a simple reduction from one year to the next.
The Earth constantly receives energy from the Sun and therefore by the laws of thermodynamics must lose an equal amount of heat to space in the form of long waves. Up to 95% of these waves are absorbed by greenhouse gases in the atmosphere. The trapped radiation is retained within the climate system and redirected towards the surface. This process, called the ‘greenhouse effect’, is essential for the Earth not to be an uninhabitable icebox. Greenhouse gas emissions include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and fluorocarbons. These gases are produced from both natural and human sources. The combustion of fossil fuels (coal, oil and natural gas) for energy production, transport and industry are the main anthropogenic sources of CO2 emissions. According to the Global Carbon Project, in 2020, CO2 emissions from fossil fuel combustion were responsible for about 65% of total greenhouse gas emissions. The destruction of forests and the conversion of natural land into agricultural or urban land also release large amounts of CO2 into the atmosphere as well as influence the carbon cycle. According to the Global Carbon Project, deforestation and land use changes accounted for about 17% of global greenhouse gas emissions in 2020. Methane is often released during organic decomposition processes, such as animal digestion and waste decomposition. Nitrous oxide can result from the use of agricultural fertilisers and industrial processes. According to the Food and Agriculture Organisation of the United Nations (FAO), agriculture is responsible for 14% of global greenhouse gas emissions. The proportions of emissions from these sources may vary from year to year and from region to region, depending on changes in human activities and environmental policies. What does not change is that the current model of production and consumption produces emissions that drive our climate towards uninhabitability and that must be radically rethought.
The problem at the root of the climate crisis is that the natural, and beneficial, concentration of greenhouse gases in the atmosphere has been compounded by increasing emissions related to human activities dependent on fossil fuels and environmental degradation, causing severe imbalances and rising temperatures. This increase in turn sets in motion some processes, such as the melting of icecaps, which reduce the Earth’s ability to reflect heat from the sun causing a vicious warming cycle, or others, such as the melting of permafrost, which threaten to create massive new sources of emissions.