Below, we identify the main types of greenhouse gases.
We also look at these greenhouse gases across several indicators/metrics to get an idea of which one might be ‘the worst’, and why.
Summary – The Different Greenhouse Gases, & Which One Might Be The Worst
Firstly, Why Do Greenhouse Gas Emissions Matter?
A key reason that greenhouse gas emissions are considered important is because of the potential impact they may have on a changing climate
What Are The Different Greenhouse Gases?
Carbon dioxide might be considered the main greenhouse gas, along with methane and also nitrous oxide
We list other greenhouse gases such as the ‘F Gases’ below
How Have We Assessed Which Greenhouse Gas Might Be The Worst?
We’ve considered three main indicators for assessing which greenhouse gas might be worst.
Those indicators are:
1. Which greenhouse gas is emitted the most
This is the quantity of each gas, usually in tonnes
2. Which greenhouse gas traps the most heat
This refers to the ‘global warming potential’ of the different gases
GWP, along with emission quantities, both relate to 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
Mainly, the number of years each gas stays in the atmosphere before it leaves
This may impact how long each gas can impact the climate for
Which Greenhouse Gas Is Emitted The Most – Global, By Quantity
Carbon dioxide is the greenhouse gas that is emitted the most globally, when measuring quantity/volume of CO2e
Which Greenhouse Gas Is Emitted The Most – Global, By % Share
Globally, carbon dioxide is the greenhouse gas that is emitted the most by a significant margin, when measuring as a % share of total greenhouse gas emissions
Which Greenhouse Gas Is Emitted The Most – In The United States, By % Share
In the US, carbon dioxide is the greenhouse gas that is emitted the most by a significant margin, when measuring as a % share of total greenhouse gas emissions
Which Greenhouse Gas Is Emitted The Most – In China, By Quantity
In China, carbon dioxide is the greenhouse gas that is emitted the most by a significant margin, when measuring quantity of CO2
Which Greenhouse Gas Traps The Most Heat/Is Most Potent? – Global Warming Potential
Below, we explain what GWP is, and list the GWP of each greenhouse gas
Sulfur Hexafluoride (SF₆) has the highest GWP of all greenhouse gases by a significant margin
What Do We Use SF₆ /Sulfur Hexafluoride For?
With SF6 being the greenhouse gas with the highest GWP value, we’ve outlined some of it’s current uses below
Which Greenhouse Gas Stays In The Atmosphere The Longest
CO2 stays in the atmosphere far longer than the other main greenhouse gases
How Long Each Greenhouse Gas Stays In The Atmosphere
We identify how long it takes for each of the major greenhouse gases to leave the atmosphere below
CO2 In Places On Earth Other Than The Atmosphere
CO2 doesn’t just exist in the atmosphere once it’s emitted
Below, we discuss where else CO2 cycles to on Earth
Overall, Which Greenhouse Gas Might Be The Worst?
Carbon dioxide might be the ‘worst’ for several reasons
We discuss a potential answer to this question in more detail below
Water Vapor As A Greenhouse Gas
Water vapor is also greenhouse gas, and is abundant on Earth
But, we discuss it’s unique role and impact compared to other greenhouse gases, and also how it interacts with, and may create a cycle and amplification effect with CO2
What Are The Different Greenhouse Gases?
Main Greenhouse Gases
The main greenhouse gases are:
Carbon dioxide (CO2)
Methane (CH4)
Nitrous oxide (N2O)
Other Greenhouse Gases
But, other greenhouse gases also include
Hydrofluorocarbons (HFCs)
Perfluorocarbons (PFCs)
Sulphur hexafluoride (SF6).
These gases can be referred to as ‘F Gases’, or ‘Fluorinated Gases’
Additionally, although they aren’t greenhouse gases, ‘aerosols’ are reported to have a warming effect like GHGs do.
Which Greenhouse Gas Is Emitted The Most? – Global, By Quantity
Globally, carbon dioxide is the greenhouse gas that is emitted the most by a significant margin, when measuring quantity of CO2e
Methane is clearly in second, and nitrous oxide is clearly in third
From ourworldindata.org:
[Globally, the gases that were emitted the most, in thousands of tonnes of carbon dioxide equivalent, were:]
[Carbon Dioxide is first at 35.46 million thousand tonnes of carbon dioxide equivalents (kt CO₂e) – in 2012]
[Methane was second at 8.01 million – in 2012]
[Nitrous Oxide was third at 3.15 million – in 2012]
[Followed by HFC Gases at 834,435.57 in 2010, SF Gases at 174,905.39 in 2010, and PFC Gases at 78,622.31 in 2010]
Which Greenhouse Gas Is Emitted The Most? – Global, By % Share
Globally, carbon dioxide is the greenhouse gas that is emitted the most by a significant margin, when measuring as a % share of total greenhouse gas emissions
Most of this carbon dioxide might come from fossil fuels – specifically used for industrial processes
Methane is second most emitted gas by % share
From epa.gov, in 2014:
Carbon Dioxide – 76% [65% of these emissions comes from fossil fuels and industrial processes, and 11% from forestry and other land use]
Methane – 16%
[This is followed by Nitrous Oxide at 6%, and the F Gases at 2%]
Which Greenhouse Gas Is Emitted The Most – In The United States, By % Share
In the US, carbon dioxide is the greenhouse gas that is emitted the most by a significant margin, when measuring as a % share of total greenhouse gas emissions
Methane is in second
From epa.gov, in 2016:
Carbon Dioxide – 81%
Methane – 10%
Nitrous Oxide – 6%
Fluorinated Gases – 3%
Which Type Of Greenhouse Gas Is Emitted The Most – In China, By Quantity
In China, carbon dioxide is the greenhouse gas that is emitted the most by a significant margin, when measuring quantity of CO2
Methane, nitrous oxide, and fluorinated gases make up the rest
From chinapower.csis.org, in 2016:
… China emitted 10.2 Giga tonnes of CO2
[One gigatonne might be 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
Which Greenhouse Gas Traps The Most Heat/Is Most Potent? – Global Warming Potential
What Is GWP?
GWP stands for ‘Global Warming Potential’
The GWP value allows for a comparison of the warming impact of different types of greenhouse gases
ourworldindata.org indicates that:
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.
Which Greenhouse Gas Traps The Most Heat? – GWP’s Of The Different Greenhouse Gases
Sulfur Hexafluoride (SF₆) has the highest GWP of all greenhouse gases by a significant margin
Tetrafluoromethane (PFC-14), also known as carbon tetrafluoride, is in second
Carbon dioxide is at a GWP of zero
From ourworldindata.org, the GWP of the different greenhouse gases are:
SF₆ – 23,500 [Sulfur Hexafluoride]
PFC-14 – 6,630 [Tetrafluoromethane, also known as carbon tetrafluoride]
[They are followed by Nitrous oxide (N₂O) at 265, HFC-152a at 138 (1,1-Difluoroethane, or DFE), and Methane (CH₄) at 28[
[Carbon dioxide (CO₂) has the lowest GWP at 1]
What Do We Use SF₆ /Sulfur Hexafluoride For?
With SF6 being the greenhouse gas with the highest GWP value, it may be worth looking at what it’s used for
From the reports below, it appears as though it has several specialty uses
It’s use appears to have been banned or restricted some parts of Europe.
Current Uses
From pubchem.ncbi.nlm.nih.gov:
[We use sulfur hexafluoride] 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.
From wikipedia.org:
… [sulfur hexafluoride] 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.
Banning, & Control Of Use
In Europe, SF6 falls under the F-Gas directive which ban or control its use for several applications (wikipedia.org)
Which Greenhouse Gas That Stays In The Atmosphere The Longest
CO2 stays in the atmosphere far longer than the other main greenhouse gases – see the section below for data and comparisons
CO2 remains in the atmosphere longer than the other major heat-trapping gases … (ucsusa.org)
How Long Each Greenhouse Gas Stays In The Atmosphere
CO2 emissions stay in the atmosphere far longer than the other major greenhouse gases – some leaves after 100 years, but some doesn’t leave the atmosphere until up to 10,000 years.
Nitrous oxide takes the second longest to leave, whilst methane takes the shortest time, but, it does convert to CO2
According to ucsusa.org, it takes the following lengths of time for emissions of these greenhouse gases to leave the atmosphere:
[It takes about a decade for] … methane (CH4) emissions … [at which point] it converts into CO2 …
[It takes about …] a century for nitrous oxide (N2O)
… 40% [of a pulse of CO2 emissions] will remain in the atmosphere for 100 years [,] 20% will reside for 1000 years [, and] the final 10% will take 10,000 years to turn over.
CO2 In Places Other Than The Atmosphere
In addition to the CO2 that is in the atmosphere, CO2 can be absorbed by, sequestered by, or stored in several places, including but not limited to:
The ocean
The soil
Forests and trees
Other plants and vegetation
These sources act as a form of a carbon sink
Overall, Which Greenhouse Gas Might Be The Worst?
Overall, based on the indicators and metrics above, CO2 might be the worst greenhouse gas
A summarised explanation for this might be:
Other greenhouse gases like SF₆, methane and nitrous oxide have a much 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 in the atmosphere, and it also remains in the atmosphere longer than the other major heat-trapping gases
As a result, carbon dioxide might be the most damaging greenhouse gas in terms of the impact it might have on a changing or warming climate
As a brief 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.
Beyond the above things, CO2’s relationship with water vapor, and the impact they may have on Earth’s temperature, may be an additional reason CO2 emissions can an issue.
We discuss water vapor as a greenhouse gas in the section below.
ucsusa.org uses the ‘RF value’ of carbon dioxide to illustrate it’s potential impact:
[Greenhouse gases are climate drivers, and each climate driver has a] “radiative forcing” (RF) [value] … [which is] 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.
A Note On Water Vapor As A Greenhouse Gas
Water vapor is an abundant greenhouse gas, but it doesn’t stay in the atmosphere for anywhere near the length that CO2 does
It may however create a cycle with CO2 that amplifies the temperature and heating of the atmosphere and Earth
The more CO2 that is emitted, the more water that evaporates and increases Earth’s temperature.
An increased temperature on Earth leads to a higher capacity to hold more water vapor.
This cycle can repeat over and over.
Abundance Of Water Vapor
Water vapor is Earth’s most abundant greenhouse gas (climate.nasa.gov)
How Long Water Vapor Stays In The Atmosphere, & How It Differs To CO2
… 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 (ucsusa.org)
Potential Role & Impact Of Water Vapor
[Water vapor is] responsible for about half of Earth’s greenhouse effect … (climate.nasa.gov)
From ucsusa.org:
[Water vapor might be considered an amplifier of the greenhouse effects, where] 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.
[As the temperature of the atmosphere increases, the more] water vapor [it might be able to hold]
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://pubchem.ncbi.nlm.nih.gov/compound/Sulfur-hexafluoride
6. https://en.wikipedia.org/wiki/Sulfur_hexafluoride
7. https://climate.nasa.gov/ask-nasa-climate/3143/steamy-relationships-how-atmospheric-water-vapor-amplifies-earths-greenhouse-effect/
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