Global Warming Potential

Every year, we pump over 35 billion tonnes of greenhouse gases into the air. These gases trap heat and raise the planet’s temperature.¹ But, these gases are not all the same.

Some, such as methane, do far more damage to the environment and raise temperatures faster than CO2, for example.² But, how can we easily measure this and show the impact of these gases? This is where the Global Warming Potential (GWP) measure acts as a useful guide.

What is the Global Warming Potential (GWP)?

The Global Warming Potential of a gas is how much damage it causes, comparable to one unit of CO2, over one hundred years.

Imagine a factory that emits 100 tons of CO2 and 100 tons of methane into the air every year. Since methane is far worse for climate change than CO2, scientists convert it and other greenhouse gases into their CO2 equivalent. This unit of measurement for each gas is called its Global Warming Potential.

As methane is regarded as roughly 28 times worse than CO2 over a one hundred period, we can say that the factory emits 100 tons of CO2 and 2,800 tons of CO2 equivalent gases. Alternatively, it is equal to a total of 2,900 tons of carbon dioxide equivalent (CO2e) in emissions.

GWP makes it easier for the public to understand this and for scientists to have a simple measure.³

What does the GWP of a gas depend on?

The GWP of a gas depends on two factors. Firstly, how well the gas traps heat in the atmosphere, and secondly, how long it takes to break down. Put simply, it is the amount of heat absorbed by a greenhouse gas in the atmosphere, compared to the same mass of carbon dioxide.

What does the GWP measure offer?

The GWP measure offers us a standard scale for measuring the climate effects of different gases. CO2 has a GWP value of 1, as it is the baseline, and it stays in the atmosphere for thousands of years. Methane has a GWP value of 28 to 36 over one hundred years. While it is far worse for trapping heat in the atmosphere, it also breaks down within a decade.⁴

Which greenhouse gas has the highest Global Warming Potential (GWP)?

A gas will have a higher Global Warming Potential (GWP) figure depending on how much more heat it can trap than CO2 and how long it stays in the atmosphere. A gas such as nitrous oxide (N2O) has a GWP 265 to 298 times that of carbon dioxide over one hundred years. It remains in the atmosphere for more than one hundred years on average.⁵

Other gases and their Global Warming Potential (GWP)

Some gases, such as chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs) and perfluorocarbons (PFCs), which can be used in household products, can have GWPs in tens of thousands.⁶ By using the GWP method of calculation, scientists can differentiate between gases that are toxic for different periods of time. For example, the Global Warming Potential for methane would be higher if it lasted longer in the atmosphere.

GWP changes

The GWP measure of a gas can also change over time, as scientists better understand its impact or its impact is adjusted depending on other gases. The GWP is also presented as ranges rather than specific numbers as there are multiple ways to calculate the measure.⁷

Can carbon capture eliminate global warming?

Carbon capture and storage (CCS) technology is frequently misunderstood as a saviour for global warming. The aim of CCS technology is to capture carbon dioxide from large sources of emissions, such as power plants or factories, before they are released into the air. This makes CCS technology a potentially valuable tool to slow down climate change and prevent global warming. But, critics say the technology is too small-scale.⁸

How much CO2 can we reduce with CCS?

Even if all CCS projects were all fully operational worldwide, they would capture only around 130 million tonnes of CO2 every year. But the world emits approximately 35 billion tonnes of carbon dioxide. So far, it’s impact has been a drop in the ocean.⁹ 

Nevertheless, CCUS technology is expected to play a part in the future, especially for industries that cannot decarbonise quickly. For example, steel and cement companies say decarbonisation would cost hundreds of billions of dollars and, so far, they are unwilling to spend the money to decarbonise.¹⁰

Carbon capture is not carbon removal

It is important to note that carbon capture is different from carbon removal. The latter removes carbon dioxide from the air, whereas the former captures some of it at the source. Carbon capture does not remove CO2 from the air, it merely slows down emissions. So, even if CCS technology had widespread use, it would not reduce carbon emissions already in the atmosphere.¹¹

^{Why is the GWP measure important?}

The Global Warming Potential measure gives us a better understanding and measure of harmful greenhouse gases emitted into the atmosphere. But, now we need to do the hard part – cutting emissions and removing CO2 from the air.

1. Ritchie, H. and Roser, M. (2020). CO2 and other Greenhouse Gas Emissions. [online] Our World in Data. Available at: https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions.
2. Environment. (2019). Methane facts and information. [online] Available at: https://www.nationalgeographic.com/environment/article/methane.
3. US EPA,OA (2019). Understanding Global Warming Potentials | US EPA. [online] US EPA. Available at: https://www.epa.gov/ghgemissions/understanding-global-warming-potentials.
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6. US EPA,OA (2019). Understanding Global Warming Potentials | US EPA. [online] US EPA. Available at: https://www.epa.gov/ghgemissions/understanding-global-warming-potentials.
7. US EPA,OA (2019). Understanding Global Warming Potentials | US EPA. [online] US EPA. Available at: https://www.epa.gov/ghgemissions/understanding-global-warming-potentials.
8. Aronoff, K. (2020). Carbon Capture Is Not a Climate Savior. [online] The New Republic. Available at: https://newrepublic.com/article/160754/carbon-capture-not-climate-savior [Accessed 12 Mar. 2021].
9. IEA. (n.d.). Carbon capture, utilisation and storage – Fuels & Technologies. [online] Available at: https://www.iea.org/fuels-and-technologies/carbon-capture-utilisation-and-storage.
10. “Green steel”: the race to clean up one of the world’s dirtiest industries. (2021). The Financial Times. [online] 15 Feb. Available at: https://www.ft.com/content/46d4727c-761d-43ee-8084-ee46edba491a.
11. American University. (n.d.). Explaining Carbon Removal. [online] Available at: https://www.american.edu/sis/centers/carbon-removal/explaining-carbon-removal.cfm.