Which Greenhouse Gas Is The Worst?

There might be a few main considerations when assessing which greenhouse gas is the worst (in relation to how much they contribute to climate change).

In this guide, we outline what those considerations might be, as well as list other information relevant to the main greenhouse gases.

 

Summary – Which Greenhouse Gas Is The Worst

– Three Main Considerations For Assessing The Worst Greenhouse Gas

1. Which greenhouse gas is emitted the most 

The volumes/quantities of each gas 

 

2. Which greenhouse gas traps the most heat/is the most potent

This is the global warming potential of each gas 

This also helps with CO2e calculations because each gas can be converted into one consolidated number based on their GWPs and quantities

 

3. How long each gas stays in the atmosphere

In terms of how many years

This helps with knowing the time period that each gas can have an impact on warming

 

– Which Greenhouse Gas Is Emitted The Most 

Globally, there is far more carbon dioxide emitted (in tonnes) that any other greenhouse gas

Some data indicates 65% of this CO2 comes from fossil fuels (like coal) and industrial processes

Methane and Nitrous Oxide are the two next most abundantly emitted GHGs

The F Gases make up most of the rest of the emissions

On a country level, different greenhouse gases can be emitted in different %’s compared to each other, and even emissions in States and Provinces within countries can vary significantly

In the two biggest emitting countries in the world, China and the US, CO2 is the most commonly emitted GHG

 

– Which Greenhouse Gas Traps The Most Heat/Is The Most Potent

Global warming potential is a measurement of the relative warming impact of a type of greenhouse gas

There are other gases that have much stronger global warming potential compared to CO2

By far, the greenhouse gas with the highest GWP is SF₆ – sulfur hexafluoride (a ‘F Gas’).

It has 23,500 times the GWP of carbon dioxide

Other greenhouse gases of note are Methane and Nitrous Oxide, which have GWPs of 28 and 265 respectively 

These numbers are relative to CO2, which is the baseline of 1. To illustrate this with an example, Methane is 28 times stronger than CO2 in terms of GWP)

It’s important to note that although Carbon Dioxide has the lowest GWP of the above greenhouse gases, it is emitted in in huge quantities into our atmosphere, and also stays in the atmosphere the longest – which are some of the main reasons it the greenhouse gas that receives a lot of attention

 

– How Long Each Gas Stays In The Atmosphere

CO2 remains in the atmosphere longer than the other major heat-trapping gases emitted as a result of human activities (mainly the combustion of fossil fuels like coal)

After CO2 is emitted into the atmosphere, 40% will remain in the atmosphere for 100 years, 20% for 1000 years, and 10% will take 10,000 years to turn over

Something that might be considered in addition to how much greenhouse gas ends up in the atmosphere, is how much CO2 is absorbed by or stored in the oceans, the soil, forests and trees, and plants and vegetation 

CO2 can be sequestered and stored in soil and trees, just as an example

The ocean also absorbs CO2 from the air

So, these sources act as a form of a carbon sink that can subtract from the total CO2 emitted

 

– So, Overall, Which Greenhouse Gas Is The Worst?

Overall, CO2 is the worst greenhouse gas according to the considerations above

The explanation for this is:

Other greenhouse gases like SF₆, methane and nitrous oxide have a higher global warming potential that carbon dioxide i.e. they trap more heat in the atmosphere per molecule of gas emitted

BUT …

CO2 is emitted in much higher quantities, and it also remains in the atmosphere longer than the other major heat-trapping gases

As a result, carbon dioxide is likely the worst greenhouse gas right now

As a rough summary – CO2 is emitted at more than 4 times the quantity than the next most abundantly emitted GHG (methane), and, it can stay in the atmosphere for up to 10,000 years, compared to a decade for methane, or 100 years for nitrous oxide.

Nitrous oxide and Methane are 265 times and 28 times stronger respectively though compared to CO2 when looking at global warming potential

 

This analysis that carbon dioxide might be the worst gas for climate change seems to be supported by ucsusa.org when discussing RF value:

[greenhouse gases are climate drivers, and each climate driver has a] “radiative forcing” (RF) [value] … in other words, the net increase (or decrease) in the amount of energy reaching Earth’s surface attributable to that climate driver.

Positive RF values represent average surface warming and negative values represent average surface cooling.

In total, CO2 has the highest positive RF of all the human-influenced climate drivers …

Other gases have more potent heat-trapping ability molecule per molecule than CO2 (e.g. methane), but are simply far less abundant in the atmosphere.

 

There’s also an asterisk on water vapor and it’s relationship to carbon dioxide.

This relationship adds even more support to the claim that carbon dioxide is the worst greenhouse gas.

Water vapor only exists in the atmosphere for a matter of days.

But, the more CO2 that is emitted the more water evaporates and increases Earth’s temperature.

An increased temperature leads to a higher capacity to hold more water vapor.

 

What Are The Different Greenhouse Gases?

The main greenhouse gases are:

Carbon Dioxide

Methane

Nitrous Oxide

 

There’s also:

F Gases

 

What Greenhouse Gas Is Emitted The Most By Volume/Quantity Globally?

Globally, carbon dioxide is by far emitted the most of any greenhouse gas in terms of volume/quantity.

 

Globally, the gases by type, in thousands of tonnes of carbon dioxide equivalent, are:

Carbon Dioxide – 35.46 million, thousand tonnes of carbon dioxide equivalents (kt CO₂e), in 2012

Methane – 8.01 million, thousand tonnes of carbon dioxide equivalents (kt CO₂e), in 2012

Nitrous Oxide – 3.15 million, thousand tonnes of carbon dioxide equivalents (kt CO₂e), in 2012

HFC Gases – 834,435.57 thousand tonnes of carbon dioxide equivalents (kt CO₂e), in 2010

SF Gases – 174,905.39 thousand tonnes of carbon dioxide equivalents (kt CO₂e), in 2010

PFC Gases – 78,622.31 thousand tonnes of carbon dioxide equivalents (kt CO₂e), in 2010

– ourworldindata.org

 

What Greenhouse Gas Is Emitted The Most By % Share Globally?

Globally, carbon dioxide is by far emitted the most of any greenhouse gas in terms of % share compared to other greenhouse gases, and most of it comes from fossil fuels and industrial processes.

 

In 2014:

Carbon Dioxide – 76% (65% from fossil fuels and industrial processes, and 11% from forestry and other land use)

Methane – 16%

Nitrous Oxide  – 6%

F Gases – 2%

– epa.gov

 

Which Greenhouse Gas Is Emitted The Most In The United States

In the US, carbon dioxide is by far emitted the most of any greenhouse gas in terms of % share compared to other greenhouse gases.

 

In 2016:

Carbon Dioxide – 81%

Methane – 10%

Nitrous Oxide – 6%

Fluorinated Gases – 3%

– epa.gov

 

Which Type Of Greenhouse Gas Is Emitted The Most In China

In China, carbon dioxide is by far emitted the most of any greenhouse gas in terms of volume/quantity and % share compared to other greenhouse gases.

 

In 2016, China emitted 10.2 Giga tonnes of CO2 (one gigatonne is equal to one billion tonnes)

Methane (CH4), nitrous oxide (N2O), and fluorinated gases collectively account for nearly 20 percent of the country’s total emissions

– chinapower.csis.org

 

Global Warming Potential Of Each Greenhouse Gas

Carbon dioxide has the lowest GWP, and the F gases have the higher GWP.

 

GWP measures the relative warming impact of one unit mass of a greenhouse gas relative to carbon dioxide.

A GWP₁₀₀ value of 28 therefore means one tonne of methane has 28 times the warming impact of one tonne of carbon dioxide over a 100-year timescale.

The GWP’s of different Greenhouse Gases are:

SF₆ – 23,500 [Sulfur Hexafluoride]

PFC-14 – 6,630 [Tetrafluoromethane, also known as carbon tetrafluoride]

Nitrous oxide (N₂O) – 265

HFC-152a – 138 [1,1-Difluoroethane, or DFE]

Methane (CH₄) – 28

Carbon dioxide (CO₂) – 1

– ourworldindata.org

 

How Do We Use SF₆ /Sulfur Hexafluoride?

It has specialty uses, and has been banned in some capacity in some parts of Europe.

 

[we use it] mainly as a test gas in respiratory physiology

Other uses include its injection in vitreoretinal surgery to restore the vitreous chamber and as a tracer in monitoring the dispersion and deposition of air pollutants.

– pubchem.ncbi.nlm.nih.gov

 

… it is used as a gaseous dielectric medium in the electrical industry. 

Other main uses include an inert gas for the casting of magnesium, and as an inert filling for insulated glazing windows.

In Europe, SF6 falls under the F-Gas directive which ban or control its use for several applications

– wikipedia.org

 

How Long Each Greenhouse Gas Stays In The Atmosphere

CO2 stays in the atmosphere far longer than the other major greenhouse gases.

CO2 stays in the atmosphere for hundreds to thousands of years, compared to methane and nitrous oxide at 10 years, and 100 years, respectively.

 

CO2 remains in the atmosphere longer than the other major heat-trapping gases emitted as a result of human activities. 

It takes about a decade for methane (CH4) emissions to leave the atmosphere (it converts into CO2) and about a century for nitrous oxide (N2O).

After a pulse of CO2 is emitted into the atmosphere, 40% will remain in the atmosphere for 100 years and 20% will reside for 1000 years, while the final 10% will take 10,000 years to turn over. 

– ucsusa.org

 

A Note On Water Vapor As A Greenhouse Gas

Water vapor only exists in the atmosphere for a matter of days.

But, the more CO2 that is emitted the more water evaporates and increases Earth’s temperature.

An increased temperature leads to a higher capacity to hold more water vapor.

 

Water vapor is the most abundant heat-trapping gas …

… water vapor has a short cycle in the atmosphere (10 days on average) before it is incorporated into weather events and falls to Earth, so it cannot build up in the atmosphere in the same way as carbon dioxide does.

However, a vicious cycle exists with water vapor, in which as more CO2 is emitted into the atmosphere and the Earth’s temperature rises, more water evaporates into the Earth’s atmosphere, which increases the temperature of the planet.

The higher temperature atmosphere can then hold more water vapor than before.

– ucsusa.org

 

Sources

1. https://www.ucsusa.org/global-warming/science-and-impacts/science/CO2-and-global-warming-faq.html#.W855shMzbR1

2. https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions

3. https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data

4. https://chinapower.csis.org/china-greenhouse-gas-emissions/

5. https://www.ucsusa.org/global-warming/science-and-impacts/science/CO2-and-global-warming-faq.html#.W855shMzbR1 

6. https://pubchem.ncbi.nlm.nih.gov/compound/Sulfur-hexafluoride

7. https://en.wikipedia.org/wiki/Sulfur_hexafluoride

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