Oil and Gas Lawyer Blog
MIT’s Casey Crownhart publishes a newsletter called The Spark. Here is his list of greenhouse gasses and their potency:
Carbon dioxide: The leading actor
I couldn’t in good conscience put together a list of greenhouse gases and not at least mention the big one. Human activities released 37.4 billion tons of carbon dioxide into the atmosphere in 2023. It’s the most abundant greenhouse gas we emit, and the most significant one driving climate change.
It’s difficult to nail down exactly how long CO2 stays in the atmosphere, since the gas participates in a global carbon cycle—some will immediately be soaked up by oceans, forests, or other ecosystems, while the rest lingers in the atmosphere for centuries.
Carbon dioxide comes from nearly every corner of our economy—the largest source is power plants, followed by transportation and then industrial activities.
Methane: The flash in the pan
Methane is also a powerful contributor to climate change, making up about 30% of the warming we’ve experienced to date, even though carbon dioxide is roughly 200 times more abundant in the atmosphere.
What’s most different about methane is that the gas is very short-lived, having a lifetime of somewhere around a decade in the atmosphere before it breaks down. But in that time, methane can cause about 86 times more warming than an equivalent amount of carbon dioxide. (Quick side note: Comparisons of greenhouse gases are usually made over a specific period of time, since gases all have different lifetimes and there’s no one number that can represent the complexity of atmospheric chemistry and physics.)
Methane’s largest sources are the fossil-fuel industry, agriculture, and waste. Cutting down leaks from the process of extracting oil and gas is one of the most straightforward and currently available ways to slim down methane emissions. There’s a growing movement to track methane more accurately—with satellites, among other techniques—and hold accountable the oil and gas companies that are releasing the most.
Nitrous oxide: No laughing matter
You may have come across nitrous oxide at the dentist, where it might be called “laughing gas.” But its effects on climate change are serious, as the gas makes up about 6% of warming to date.
Nitrous oxide emissions come almost entirely from agriculture. Applying certain nitrogen-based fertilizers can release the gas as bacteria break those chemicals down. Emissions can also come from burning certain agricultural wastes.
Nitrous oxide emissions grew roughly 40% from 1980 to 2020. The gas lasts in the atmosphere for roughly a century, and over that time it can trap over 200 times more heat than carbon dioxide does in the same period.
Cutting down on these emissions will largely require careful adjustment of soil management practices in agriculture. Decreasing use of synthetic fertilizers, applying the fertilizer we do use more efficiently, and choosing products that eliminate as many emissions as possible will be the main levers we can pull.
Fluorinated gases: The quiet giants
Last but certainly not least, fluorinated gases are some of the most powerful greenhouse gases that we emit. A variety of them fall under this umbrella, including hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and SF6. They last for centuries (or even millennia) in the atmosphere and have some eye-popping effects, with each having at least 10,000 times more global warming potential than carbon dioxide.
HFCs are refrigerants, used in air conditioners, refrigerators, and similar appliances. One major area of research in heat pumps seeks alternative refrigerants that don’t have the same potential to warm the planet. The chemicals are also used in aerosol cans (think hair spray), as well as in fire retardants and solvents.
SF6 is used in high-voltage power equipment, and it’s the single worst greenhouse gas that’s been covered by the International Panel on Climate change, clocking in at 23,500 times more powerful than carbon dioxide over the course of a century. Scientists are trying to find alternatives, but it’s turning out to be a difficult switch—as you’ll see if you read my latest story.
The good news is that we know change is possible when it comes to fluorinated gases. We’ve already moved away from one category, chlorofluorocarbons (CFCs). These were generally used in the same industries that use HFCs today, but they had the nasty habit of tearing a hole in the ozone layer. The 1987 Montreal Protocol successfully spurred a phaseout of CFCs, and we would be on track for significantly more warming without the change.