Updated: Mar 31
If you have completed Unit 1 of the Carbon Voice Curriculum (CVC), you know that greenhouse gases (GHG) naturally occur in the atmosphere. But human activities produce excessive GHGs in the atmosphere, leading to global warming and climate change. In this article, we will dive a little deeper into each GHGs, where they come from, and what can be done to stop too much of them from entering the atmosphere.
What is GHG?
The term greenhouse gas (GHG) is defined as "a gaseous compound with the ability to trap heat or longwave radiation in the Earth’s atmosphere." Some occur naturally in the Earth’s atmosphere; these include carbon dioxide (CO2), methane (CH4), water vapor (H2O), and nitrous oxide (N2O). However, human activities are increasing the presence of some of these gases through the burning of fossil fuels, industrial processes, land-use changes, as well as the introduction of harmful synthetic compounds into the atmosphere. The Kyoto Protocol has further classified three categories of these man-induced greenhouse gases, which include: Chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF6).
GHGs trap heat from the Sun, acting as a blanket that keeps our Earth at just the right temperature for life as we know it. Without this greenhouse effect, Earth would have a temperature of -18 degrees Celsius. However, human activity is increasing the amount of greenhouse gases in the atmosphere, which means excess heat is absorbed, leading to global warming.
The most abundant greenhouse gas
So which gases are the main offenders when it comes to climate change? As you might expect, they are the ones with natural processes but are currently exacerbated by human activities: carbon dioxide, methane, and nitrous oxide.
Carbon Dioxide (CO2)
This is one of the most widely known greenhouse gases and a global priority in terms of reducing emissions. To date, the concentration of CO2 has risen by about 40% since the industrial revolution. Fossil fuel burning was the biggest culprit of CO2 release into the atmosphere - accounting for about 87% of all human-produced gas, followed by deforestation ( 9%) and industrial processes (4%).
On the bright side, the International Energy Agency (IEA) noted an exponential increase in global renewable electricity generation. By the end of 2021, an additional 290 gigawatts (GW) had been installed. This action is a sign that a new global energy economy is emerging. By 2026, global renewable electricity is forecasted to increase up to 60%.
Methane comes from two main sources: biological and geological, both of which can include human factors. Human factors commonly include raising livestock, cultivating rice, and burning biomass and biofuels. Every kilogram of methane emitted into the atmosphere has the equivalent impact of 30 times that of CO2 over 100 years on Earth’s climate. Data released by the US National Oceanic Atmospheric Administration (NOAA) showed that methane levels have been growing exponentially since 2007.
Although the methane trends on the graph proved somewhat unpredictable, Xin Lan, an atmospheric scientist at NOAA, suggests that anthropogenic (human) sources such as livestock, agricultural waste, landfill, and fossil-fuel extraction accounted for at least 62% of total methane emissions since 2007. Since there is only one main global methane sink, and its process occurs deep in the troposphere (the lowest layer of the Earth’s atmosphere), the Global Methane Pledge was enacted to encourage countries to cut emissions by 30% by 2030 from 2020 levels. Despite concerns about NOAA’s trends, over 100 countries have pledged to move towards a more sustainable future.
Nitrous Oxide (N20)
This is another potent greenhouse gas in the atmosphere. One kilogram of N20 released into the atmosphere has a global warming effect equivalent to 298 kg of carbon dioxide over a 100-year period. Since the industrial revolution, the concentration of N20 has increased by roughly 15%. According to the IPCC, the largest human source of nitrous oxide emissions is agriculture (67%), which creates both direct and indirect emissions. Direct emissions come from fertilized agricultural soils and livestock manure (42%), while indirect emissions come from runoff and leaching-off fertilizers (25%). Data from the IPCC 5th assessment report noted that the agriculture sector emits about 4.5 million tonnes of nitrous oxide per year, suggesting that the agriculture sector has worsened over the years.
International organizations like the WWF acknowledge the adverse impacts associated with agricultural operations. Thus, WWF continues to implement better management practices for agriculture by creating financial incentives, improving agricultural policies, and convening multi-stakeholder roundtables that define and reduce the impacts of priority commodities.
What does the future hold?
The detrimental effects of greenhouse gas emissions are evident. To tackle climate change and its negative impacts, world leaders at the UN climate change conference (COP21) published a legally-binding international treaty called The Paris Agreement. One of the long-term goals stated in the agreement is to substantially reduce global GHG emissions to limit the global temperature increase to 2°C while pursuing efforts to limit the increase even further to 1.5 degrees.
However, data from Climate Tracker 2021 shows that if we continue with current trajectories, average global temperatures are expected to be around 2.9°C higher than pre-industrial levels. Even the optimistic scenarios show that keeping this change under 1.5°C seems incredibly challenging.
“Action on climate change is urgent. The more we delay, the more we will pay in lives and money,” said Ban Ki-Moon, former secretary general of the United Nations, warning nation leaders during the UN general assembly.
To enable climate action in our daily life, understanding the fundamentals of GHG emissions due to human activities in combination with other climate knowledge (such as carbon offsetting and blue carbon ecosystem) is essential.
Writer: Callista Daniella
Editor: Howen Jayawi
Cornwall, W. (2022, February 20). Humans are a bigger source of climate-altering methane, new studies suggest. Science.org. https://www.science.org/content/article/only-humans-can-create-climate-altering-methane-burns-new-studies-suggest
(2021, December 1). Renewable electricity growth is accelerating faster than ever worldwide, supporting the emergence of the New Global Energy Economy - News. IEA. Retrieved July 28, 2022, from https://www.iea.org/news/renewable-electricity-growth-is-accelerating-faster-than-ever-worldwide-supporting-the-emergence-of-the-new-global-energy-economy
Main sources of nitrous oxide emissions. What's Your Impact. (2017, July 8). Retrieved July 26, 2022, from https://whatsyourimpact.org/greenhouse-gases/nitrous-oxide-emissions
Temperatures. Climate Action Tracker. (n.d.). Retrieved July 26, 2022, from https://climateactiontracker.org/global/temperatures/
Tollefson, J. (2022, February 8). Scientists raise alarm over 'dangerously fast' growth in atmospheric methane. Nature News. Retrieved July 26, 2022, from https://www.nature.com/articles/d41586-022-00312-2