Climate Protection: What are “fossil fuels’? What are ‘greenhouse gases’?

A car’s tailpipe, from which exhaust is released. (Photo by Nick Maxwell)

I recently spoke at a meeting about burning fossil fuels and how they release greenhouse gases that overheat the planet. When we got to audience questions, the last question turned out to be something that probably should have gone first: “What is a ‘fossil fuel’? And what are ‘greenhouse gases’?”

Sensible questions. The short answers are the fossil fuels are oil, natural gas, and coal, and the greenhouse gases are carbon dioxide, methane, nitrous oxide and fluorinated compounds. Well, there’s a mouthful. So what are they?

Fossil fuels


Oil is the largest source of U.S.-caused global overheating. Gasoline and diesel are refined from oil. When you fill up at a gas station, you are pumping a fossil fuel into your gas tank.

Your car runs by burning gasoline in your engine. When you burn gasoline, the burning creates water molecules and carbon dioxide.

If you drive a diesel truck, the same thing happens. Diesel burns into water and carbon dioxide that is released into the air.

That carbon dioxide is the stuff that got us into our global warming mess. Carbon dioxide is the biggest problem in greenhouse gases. For thousands of years, there were about two trillion tons of carbon dioxide in the air around the world. Since 1900, we added another trillion tons, increasing global carbon dioxide by 50%.

Jet fuel is refined from oil. Jet fuel contains the same kinds of molecules that burn into water and carbon dioxide; a flight to Hawaii releases carbon dioxide.

Propane is one of the chemicals that refineries get out of oil. When you light your camp stove, the propane burns into water and carbon dioxide. Propane stoves release the same carbon dioxide that is causing higher temperatures around the world.

Natural gas

Natural gas is the fossil fuel making the second-largest contribution to U.S. global heating. Natural gas molecules are very similar to petroleum oil molecules. Like oil molecules, they are made from carbon atoms and hydrogen atoms.

Most of the gas pumped into homes is methane. Methane burns like oil. Like oil, methane is made of carbon atoms and hydrogen atoms. As with gasoline, the hydrogens combine with oxygen to make water and the carbons combine with oxygen to make carbon dioxide.

Depending on the local gas utility, the gas pumped into your neighbors’ homes is between 67% and 97% methane. The rest of the pumped gas is mostly other gases (like propane) that burn into water and carbon dioxide.

When you light a gas stove, the flame starts releasing water vapor and carbon dioxide. (Natural gas also releases a variety of other pollutants. You need to have good ventilation for a gas stove.)

You may have seen advertising suggesting that natural gas “is the green energy,” and implying that natural gas doesn’t create greenhouse gases. Nope. The way ads can get away with saying that is, for a given amount of generated heat, natural gas releases less carbon dioxide. Not no carbon dioxide; just less.

For no carbon dioxide, you need existing solar panels, windmills, hydroelectric dams or nuclear power plants. Those are the “green energy” sources (although you might question whether radioactive waste from nuclear plants counts as “green”).


Coal used to be a bigger deal for global warming, but U.S. coal burning has dropped by more than half since 2007 as the U.S. switched from coal power plants to natural gas power plants. That’s a good thing. For a given amount of electricity, coal creates more global overheating pollution than gas.

Coal is mostly the same stuff as oil and gas. It is made of carbon atoms and hydrogen atoms. When a power plant burns coal, it makes carbon dioxide and water.

Coal also has a bunch of other stuff in it, so a power plant releases a bunch of other pollutants when it burns coal. As far as global warming is concerned, the big deal is that coal releases carbon dioxide.

Currently, in the U.S., coal burning creates about half as much carbon dioxide as gas or oil.

What are the greenhouse gases?

There are four greenhouse gases: carbon dioxide, methane, nitrous oxide and fluorinated compounds.

Carbon dioxide

Carbon dioxide is the big deal in greenhouse gases. Carbon dioxide produces 80% of the global heating from the U.S. Carbon dioxide stops infrared heat radiation that is headed to outer space and sends some of it back towards Earth.

Carbon dioxide is released when you drive a gasoline car or diesel truck, when you heat your home with natural gas, or when a power plant burns coal.


Methane causes 11% of the global heating pollution from the U.S. That is one seventh of the global heating of carbon dioxide.

The largest sources of methane in the U.S. are the oil, natural gas and coal industries. Methane leaks out of natural gas pipes and from coal mines and oil wells. That provides a nice side benefit: stop the fossil fuel industries and you stop a third of the methane releases.

Methane also comes from cattle gas and rotting sewage and landfills.

When someone wants to convince you of the importance of methane, they will point out that, if you have equal quantities of methane and carbon dioxide, the methane will produce about 28 times as much global warming.

That is true, but we release a lot less methane than carbon dioxide. If you have a choice of stopping methane or stopping carbon dioxide, please stop the carbon dioxide first. U.S. carbon dioxide causes seven times as much warming. Stop burning gasoline and natural gas, and you stop almost all U.S. global warming pollution.

Nitrous Oxide

Nitrous oxide causes 6% of the U.S. global heating pollution. U.S. carbon dioxide creates 13 times as much heating as nitrous oxide.

Nitrous oxide mostly comes from farms using older farming practices. We have innovations that will stop most nitrous oxide emissions.

Fluorinated compounds

The fourth greenhouse gas, fluorinated compounds, is actually a collection of gases. There are dozens of fluorinated compounds.

Fluorinated compounds are man-made chemicals used in machines that move heat, like refrigerators, air conditioners and heat pumps. Fluorinated compounds get released when they leak out of those machines. That is why you have to throw out refrigerators at specialized facilities that capture the gases.

Altogether, fluorinated compounds cause 3% of the global heating from U.S. greenhouse gases.

As with nitrous oxide, we already have solutions for replacing fluorinated compounds and stopping almost all their global heating.

That’s it

The fossil fuels are oil (and the products made from oil, like gasoline), natural gas (which is mostly methane), and coal. The greenhouse gases are carbon dioxide (80% of the problem), methane (11%), nitrous oxide (6%), and fluorinated compounds (3%).

— By Nick Maxwell

Nick Maxwell is a certified climate action planner at Climate Protection NW, teaches about climate protection at the Creative Retirement Institute and serves on the Edmonds Planning Board.


  1. In atmospheric sciences, we consider greenhouse gasses to be any gas that absorbs and emits strongly in the infrared/thermal/longwave part of the spectrum, however they get into the atmosphere. These are the gasses that then (in brief) result in more energy staying in earth’s atmosphere, rather than escaping to space. Water vapor is one of the strongest greenhouse gasses, but we treat it differently because unlike the gasses you listed, it can change phase, and so it self-regulates.
    It’s still problematic, though. As the atmosphere warms, the equilibrium point for water vapor goes up, meaning there’s more water vapor in the air, and it contributes more to trapping that longwave energy. It’s a feedback that the other gasses produce, and it’s an automatic adjustment nature makes.

    1. Yes. Thanks! I have seen reports that any additional water added to the atmosphere without changing the temperature usually just falls out within a few weeks.
      For that reason, the water that comes out of burning gasoline, natural gas, and coal is not considered a cause of global warming, just the carbon dioxide (and any methane that is released).

  2. Golly and Gee Whiz Mr. Science. Does that mean we are all going to die of something someday because there are just too many of us burning too much fossil fuel or is everyone going to die of something sooner or later, no matter what we do? There is nothing wrong with pushing for and developing cleaner sources of energy but making a crusade out of it to save future generations that are way more apt to die in a Nuclear War created by a Sociopath or Psychopath political leader strikes me as a fools mission not worth pursuing.

    1. Clinton, you have me thinking of Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb. I don’t think anyone has made a climate change equivalent. They might try, but no one could match Peter Sellers, anyway.

  3. Before we started using fossil fuels where did the carbon dioxide come from? What was causing it? I know plants and trees sequester it so there must be a large source especially since there was a constant 2 trillion tons in the atmosphere. Why is it a lot of it is good but more of it is bad? Seems that it rises naturally during warm periods and reduces during cold periods they say 180 parts per million during the last ice age 400 today and 4000 during the dinosaurs humans weren’t around yet but it is obvious life was flourishing. Sorry but I ain’t buying into the emergency carbon dioxide was here before us and will be here after us the earth will warm and at some point it will cool and carbon dioxide will go up and down with it.

    1. Yes, Jim. You got it right. 20,000 years ago, when carbon dioxide was doing the least to keep the planet warm, the carbon dioxide was 190 parts per million (PPM). It was so cold, there was a glacier two miles thick over Toronto. So much water was frozen in polar glaciers that a Texas-sized land, Beringia, was exposed between what is now Alaska and Northeastern Russia.
      A thaw started in 16,000 BCE. Carbon dioxide levels grew 1 PPM per century, bringing carbon dioxide up 75 PPM by 9,000 BCE. Receding glaciers exposed Toronto. Beringia was submerged.
      That’s what we got with an increase of 75 PPM. From 9,000 BCE to 1850, carbon dioxide rose by 0.2 PPM per century, getting to 285, 20 PPM higher. In the last 174 years, carbon dioxide rose by 139 PPM.
      The problem is not the level. The problem is the change. Seattle got to 107 °F in 2021. 107 °F is not in itself terrible. It gets over 107 °F in Death Valley every year.
      The problem is the change. Raising temperatures to 107 °F in Seattle where summers rarely got over 90 °F kills people.
      Luckily, when we stop burning fossil fuels, we will almost entirely stop the change.
      The faster we stop the change, the fewer people die from global warming. It’s our choice.

      1. Nick people are born and die every day in this country I don’t think global warming is even on the list of what kills people if it is it is way down at the bottom. To Clintons point maybe we just have to many people trying to stay warm or cold and trying to eat and work and don’t forget travel. When more people die from climate change in this country than from drug overdose or car accidents or gun deaths let me know until then although tragic it doesn’t worry me. 2023 record global greenhouse gas emissions 2024 expected to be even higher, all the solar panels all the windmills all the electric cars all the promotion all the fear mongering has made little to no difference maybe we have slowed the increase but we certainly haven’t reduced it. One could argue all this green new deal has done is actually increased carbon emissions with the push of this new industry buildout. I do think that over time having a replacement for fossil fuels is good because fossil fuels is a finite thing that we are going to run out of sooner or later.

  4. Thanks, Nick, for a great article that clearly explains two terms – “fossil fuels” and “greenhouse gasses” that get used a lot without explanation. Methane is the one that always confuses me because, as you say, it is both a fossil fuel (most of natural gas), but also a greenhouse gas. So, if I replace my gas stove with an induction stove, I will directly reduce the carbon dioxide that goes into the atmosphere but also, indirectly, help to reduce methane, by reducing the amount of gas purchased from the gas company, whose pipelines leak methane into the air. Have I got that right?

    1. Correct! Your gas stove releases carbon dioxide and water molecules when it burns gas. And it leaks gas. And the pipes that bring the gas to your home leak gas. And the gas wells leak gas. All of those gas leaks add to the global warming too.

      1. And don’t forget cows (of which there are thousands of new ones which we observed with their moma’s when we recently drove thru freshly rained on Eastern CA.) also leak lots of methane gas which adds to global warming too. Be sure to worry about that as you predict and prepare for more gloom and doom.

  5. Nick,

    Thank you for your well written article. If you could, I would like to hear your take on what the implications are as we near the end of extracting our fossil fuel resources. By some accounts we run out of oil within the next 50 years. Within my children’s and grandchildren’s lifetime. So, one could expect that as we near this threshold the economics of supply and demand would suggest that energy prices will skyrocket. At some point prior to that, civilization will have made a decision. A decision which either sends us back to the stone age or propels us into the future.

    Your thoughts?

    1. Jim that is if new reserves aren’t found new reserves are being found all the time. That said my vague understanding is a couple of hundred years.

      1. Jim,

        While I agree that new reserves are still being found with new technologies, the flip side is that the rate of consumption is increasing as well, particularly in developing countries. The question becomes; which is increasing at a faster rate, new oil reserves or higher consumption? It’s probably safe to say, sooner or later, we will run out of oil. A literature search still seems to point to a 50-year timeframe.

        1. The problem I see is government like this one restricting areas for exploration and making through rules regulations and fees it to expensive to explore. Hence the unknown reserves. Certainly a world without fossil fuel is only a few lifetimes away either way. My guess if people like nick has their way all exploration would stop tomorrow fuel prices would go through the roof making any use prohibitively expensive. My worry would be what is next limiting how much toilet paper you can purchase as a example.

  6. Jim,
    You bring up an important point. If we run out of fossil fuels and we stuck to our gasoline cars and natural gas water heaters, it’s going to be very disruptive as we freeze and have to walk nearby farms to pick up food that cannot be delivered by truck.
    The sun is going to continue shining and the winds will continue to blow. Our electricity is going to transition over to wind and solar. If we switch to electric vehicles and electric heat pumps, whatever happens to fossil fuels won’t matter.
    There is a more immediate issue around this. Last year, Europe leapt ahead on installing heat pumps and turning off their natural gas. What as on their minds was that Vladimir Putin was trying to use gas to blackmail them into abandoning Ukraine, and they could see the writing on the wall: this year Ukraine, next year Poland, then Germany. Better to stop buying what makes Putin rich.

    1. Speaking of crazy psycho/sociopath politicians who might just blow up the world. . . . . If this happens, the sun will quit shining and we will have a long cold nuclear winter and mankind may or may not survive in some form or another. By all means, keep developing new forms of energy and using it more , but enough with the fear mongering over climate change because life is fragile and it ends sooner or later for everyone anyhow. The children and grandchildren talked about in this thread currently have a lot more to fear from war waging nut job dictators and oligarchs than they do fossil fuels in the next fifty to one hundred years anyway. This is just dumb and thoughtless – like people refusing to get on an airplane because it might crash but think nothing about riding in a car down the freeway where their chances of trauma and death are exponentially higher. Control what you can and don’t obsess over what you can’t would be my advice to all.

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