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Five things to know about the greenhouse gases that warm the planet
1. What is the greenhouse effect?
In a greenhouse, where sunlight enters and heat is retained. The greenhouse effect describes a similar phenomenon, but on a planetary scale, with the atmosphere instead of the glass of a greenhouse, certain gases increasingly increase global temperatures.
The Earth's surface absorbs just under half of the sun's energy, while the atmosphere absorbs 23%, with the rest being returned to space. Natural processes ensure that the amount of incoming and outgoing energy is equal, which keeps the temperature of the planet stable.
However, human activity is causing an increase in greenhouse gas (GHG) emissions which, unlike other atmospheric gases such as oxygen and nitrogen, are trapped in the atmosphere and cannot escape. escape from the planet. This energy returns to the surface, where it is reabsorbed.
As there is more energy flowing in than energy flowing out of the planet, surface temperatures rise until a new equilibrium is reached.
2. Why is global warmingimportant ?
This increase in temperature has long-term adverse effects on the climate and affects a multitude of natural systems. The effects include increased frequency and intensity of extreme weather events - including floods, droughts, wildfires and hurricanes - which affect millions of people and cause economic losses amounting to several trillions of dollars.
“Human-made greenhouse gas emissions endanger human and environmental health,” says the head of the United Nations Environment Program (UNEP) energy and climate branch, Mark Radka, adding that “Impacts will become more widespread and severe without strong climate action.”
GHG emissions are key to understanding and solving the climate crisis: despite an initial drop due to Covid-19, UNEP's latest emissions gap report shows a rebound, and projects a disastrous increase in the global temperature by at least 2.7 degrees Celsius this century, unless countries make much greater efforts to reduce emissions.
According to the report, GHG emissions must be halved by 2030 if we are to limit global warming to 1.5°C above pre-industrial levels by the end of the century.
3. What are the main greenhouse gases?
Water vapor is the gas that contributes the most to the greenhouse effect. However, almost all of the water vapor in the atmosphere comes from natural processes.
Carbon dioxide (CO2), methane and nitrous oxide are the main GHGs to be concerned about. CO2 stays in the atmosphere for up to 1,000 years, methane for about a decade and nitrous oxide for about 120 years.
Measured over a 20-year period, methane is 80 times more potent than CO2 in causing global warming, while nitrous oxide is 280 times more potent.
4. How human activity pproduce these greenhouse gases?
Coal, oil and natural gas continue to power many parts of the world. Carbon is the main element of these fuels which, when burned to generate electricity, power transport or provide heat, produce CO2.
Oil and gas extraction, coal mining and waste dumps account for 55% of man-made methane emissions. About 32% of man-made methane emissions are attributable to cows, sheep and other ruminants that ferment food in their stomachs. Manure decomposition is another agricultural source of this gas, as is rice cultivation.
Man-made nitrous oxide emissions come largely from agricultural practices. Bacteria in soil and water naturally convert nitrogen to nitrous oxide, but fertilizer use and runoff enhance this process by releasing more nitrogen into the environment.
Fluorinated gases - such as hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride - are GHGs that do not occur naturally. Hydrofluorocarbons are refrigerants used to replace chlorofluorocarbons (CFCs), which, after depleting the ozone layer, have been phased out thanks to the Montreal Protocol. The others have industrial and commercial uses.
Although fluorinated gases are much less prevalent than other GHGs and do not deplete the ozone layer like CFCs, they are still very potent. Over a 20-year period, the global warming potential of some fluorinated gases is up to 16,300 times greater than that of CO2.
5. What can we do to reduce GHG emissions?
Switching to renewables, pricing carbon and phasing out coal are all important elements to reduce GHG emissions. Ultimately, tougher emission reduction targets are needed to safeguard long-term human and environmental health.
According to Mr. Radka, “we need to implement strong policies that support high ambitions” and “we cannot continue on the same path and expect better results”. "We must act now," he said.
During the United Nations Climate Conference in Glasgow (COP26), the European Union and the United States launched the Global Methane Commitment, which will see more than 100 countries aim to reduce emissions by 30% methane emissions in the fuel, agriculture and waste sectors by 2030.
Despite the challenges, there are reasons to be positive. Between 2010 and 2021, policies were put in place to reduce annual emissions by 11 gigatonnes by 2030 compared to what would have happened otherwise.
By making choices that have less harmful effects on the environment, everyone can be part of the solution and influence change. Speaking out is a way to multiply impact and create change on a much larger scale.
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