1. What is the greenhouse effect?
In a greenhouse, sunlight enters, and heat is retained. The greenhouse effect describes a similar occurrence on a planetary extent but, instead of the glass of a greenhouse, certain gases are increasingly raising global temperatures.
The surface of the Earth absorbs just under half of the sun’s energy, while the air absorbs 23 per cent, and the rest is reflected back into space. Natural processes ensure that the amount of incoming and outgoing energy is equal, keeping the planet’s temperature stable.
However, human activity is resulting in the increased emission of so-called greenhouse gases (GHGs) which, unlike other atmospheric gases such as oxygen and nitrogen, becomes retained in the air, unable to escape the planet. This energy returns to the surface, where it is reabsorbed.
Because more energy enters than exits the planet, surface temperatures increase until a new balance is achieved.
2. Why does the warming matter?
This temperature increase has long-term, negative effects on the climate, and affects a myriad of natural systems. Effects include increases in the frequency and intensity of extreme weather events – including flooding, droughts, wildfires and hurricanes – that affect millions of people and cause trillions in economic losses.
“Human-caused greenhouse gas emissions endanger human and environmental health,” says Mark Radka, Chief of the UN ecosystem Programme’s (UNEP) Energy and Climate Branch. “And the impacts will become more extensive and harsh without strong climate action.”
GHG emissions are basic to understanding and addressing the climate crisis: despite an initial dip due to COVID-19, the latest UNEP Emissions Gap Report shows a rebound, and forecasts a disastrous global temperature rise of at the minimum 2.7 degrees this century, unless countries make much greater efforts to reduce emissions.
The report found that GHG emissions need to be halved by 2030, if we are to limit global warming to 1.5°C compared to pre-industrial levels by the end of the century.
3. What are the major greenhouse gases?
Water vapour is the biggest overall contributor to the greenhouse effect. However, almost all the water vapour in the air comes from natural processes.
Carbon dioxide (CO2), methane and nitrous oxide are the major GHGs to worry about. CO2 stays in the air for up to 1,000 years, methane for around a decade, and nitrous oxide for approximately 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 is human activity producing these greenhouse gases?
Coal, oil, and natural gas continue to strength many parts of the world. Carbon is the main component in these fuels and, when they’re burned to generate electricity, strength transportation, or provide heat, they produce CO2.
Oil and gas extraction, coal mining, and waste landfills explain 55 per cent of human-caused methane emissions. Approximately 32 per cent of human-caused methane emissions are attributable to cows, sheep and other ruminants that ferment food in their stomachs. Manure decomposition is another agricultural source of the gas, as is rice cultivation.
Human-caused nitrous oxide emissions largely arise from agriculture practices. Bacteria in soil and water naturally transform nitrogen into nitrous oxide, but fertilizer use and run-off add to this course of action by putting more nitrogen into the ecosystem.
Fluorinated gases – such as hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride – are GHGs that do not occur naturally. Hydrofluorocarbons are refrigerants used as alternatives to chlorofluorocarbons (CFCs), which, having depleted the ozone inner,were phased out thanks to the Montreal Protocol. The others have industrial and commercial uses.
While fluorinated gases are far less common than other GHGs and do not deplete the ozone inner like CFCs, they are nevertheless very powerful. Over a 20-year period, the global warming possible of some fluorinated gases is up to 16,300 times greater than that of CO2.
5. What can we do to reduce GHG emissions?
Shifting to replaceable energy, putting a price on carbon, and phasing out coal are all important elements in reducing GHG emissions. Ultimately, stronger emission-reduction targets are necessary for the preservation of long-term human and environmental health.
“We need to implement strong policies that back the raised ambitions,” says Mr. Radka. “We cannot continue down the same path and expect better results. Action is needed now.”
During COP26, the European Union and the United States launched the Global Methane potential, which will see over 100 countries aim to reduce 30 per cent of methane emissions in the fuel, agriculture and waste sectors by 2030.
Despite the challenges, there is reason to be positive. From 2010 to 2021, policies were put in place to lower annual emissions by 11 gigatons by 2030 compared to what would have otherwise happened. Individuals can also join the UN’s #ActNow campaign for ideas to take climate-positive actions.
By making choices that have less unhealthy effects on the ecosystem, everyone can be a part of the solution and influence change. Speaking up is one way to multiply impact and create change on a much bigger extent.
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