To know which greenhouse gas is the worst, there’s probably three factors that need to be looked at:
- Quantities that each greenhouse gas is emitted in – so you know total volumes of each gas
- Global warming potential/warming impact of the different gases – so you know the potential of each gas to trap heat in the atmosphere, and which ones are most potent
- How long the gas stays in the atmosphere – so you know how long it’s a problem for
In this guide, we look at each of these factors for each gas.
Summary – Which Greenhouse Gas Is The Worst
Overall, CO2 is the the worst greenhouse gas according to different factors.
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
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
*A variable that should be considered in addition to these things is the sequestration or absorption of CO2 from the atmosphere, into the ocean, vegetation and forests, and soil.
Consider this feedback about RF values from ucsusa.org on the impact of CO2:
- Greenhouse gases are climate drivers
- By measuring the abundance of heat-trapping gases in ice cores, the atmosphere, and other climate drivers along with models, the IPCC calculated the “radiative forcing” (RF) of each climate driver—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 compared by the IPCC
- 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.
Global Quantities Of Greenhouse Gas Emissions By Gas Type
Globally, the gas emissions 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
*Note: the quantities of GHG’s emitted by different countries, and even with states and provinces within countries can vary significantly.
Global Warming Potential/Warming Impact Of Each Greenhouse Gas
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
How Long Each Greenhouse 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.
- 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.
- This literally means that the heat-trapping emissions we release today from our cars and power plants are setting the climate our children and grandchildren will inherit.
A Note On Water Vapor As A Greenhouse Gas
- Water vapor is the most abundant heat-trapping gas, but rarely discussed when considering human-induced climate change.
- The principal reason is that 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.