Attention, Passengers: This Is Your Pre-boarding Announcement

We’ve all heard that, due to voluminous CO₂ emissions, flying isn’t great for the environment, but the question is, seriously, how bad is it? Especially if it’s just one teensy return flight, how bad can it possibly be? I’m not a celebrity with a private jet that doubles as a flying mansion. I don’t go zipping off to Italy every time I want a pizza. I’m not greedy. I think of others and that’s why I want to go to my beloved niece’s destination wedding in Cancun (I would hate to hurt her feelings), and I also want to treat my partner—just once—to that dream vacation in Thailand, or maybe just a little getaway in the south of France. Is that too much to ask? I mean, this is my one wild and precious life, to quote the poet. I don’t want to miss out, or look miserly and cold-hearted, or like an uncultured, unworldly, parochial bumpkin. If it’s just one trip—just two little flights—how much CO₂ am I actually contributing?

The following Flight Perspective Generator can help to answer that question. See how it works below. (You can check out the Celebrity Flight Perspective Generator as well, if you want to see what the flying mansion people are up to.) You’ll notice that the answer is given both in Kilograms of CO₂ but primarily in Hiroshima-sized bomb equivalents. That’s a colourful, and accurate, way of expressing the amount of heat that’s actually generated every time a plane takes to the skies.

If you like, you can ignore the following few paragraphs and skip ahead to the Flight Perspective Generator, but it will generate a whole lot more perspective if you read this first:

We’re all aware that the planet is heating up, and fast—but just how fast? It’s sometimes hard to wrap our heads around the actual numbers—they’re not only huge but also commonly expressed in units many of us don’t use day to day—so instead the question might be asked by thinking in terms of the aforementioned Hiroshima-sized nuclear bombs and putting it this way: On average, by how many Hiroshima-sized nuclear bombs does the Earth heat up every day? I asked somebody this question recently and their answer was five, which sounds reasonable given just a single bomb’s insanely destructive capacity—but, sadly, five isn’t the answer. You may already know the answer but, if you don’t, before you read on think about it for a moment and take a wild guess.

Did you answer that the earth heats up, on average, by five hundred nuclear bomb-equivalents every single day? Excellent! That is an insanely large number, right? Sadly, it’s also totally wrong.

Okay, how about five thousand? you might suggest.

No.

Fifty thousand?

Pfft.

Fine. How about a hundred thousand.

You’re getting warmer. Try half a million.

Half a million?

No.

OMG you’re irritating.

Right! So the answer is—according to the scientists who measure this stuff—that the Earth heats up, on average, by the equivalent of 1,040,000 Hiroshima-sized nuclear bombs every single day. ¹ One million and forty thousand sounds like an impossibly large number, but it’s just what happens when 8.3 billion humans go about their business burning fossil fuel, all of which results in 104 million metric tons of CO₂ being pumped into the atmosphere every day.

And what happens to all that CO₂? Importantly, a significant fraction of it stays put in the atmosphere for thousands, and even tens of thousands, of years, trapping heat and causing havoc. But here’s the kicker, and it’s a doozy. The heat that was originally released from burning the fossil fuel in the first place² “is ultimately a tiny fraction of the amount of heat trapped by CO₂ that is released by that fuel. It takes roughly two months for the heat trapped by the CO₂ to equal the heat produced by burning the fuel it came from. However, CO₂ remains in the atmosphere for many centuries, and ultimately can trap 100,000 times more heat than was produced by the fire that released it.”³, ⁴

Damn. That sounds bad, but how exactly does all this relate, specifically, to flying? I mean, I understand that every time I fly, the planet gets a little hotter, but, surely, my contribution is still bound to be so small it’s barely worth measuring.

If only. Let’s say, for example, that I live in Vancouver, British Columbia, and the lure of my niece’s destination wedding in Cancun is just too much to resist. Alrighty. If I’m lucky, I can get a direct flight on a Boeing 737 MAX 8 that gets me (and 167 other passengers) there in a little over 6 hours—a distance of about 4500 km. That flight will warm the earth directly by burning the fuel: CO₂ isn’t even in the picture yet and already that flight has burned 12,870 kg of jet fuel, releasing an astonishing 1.3% of the heat of a Hiroshima bomb. Naturally I’m flying home again, so double that number to 2.6% of a Hiroshima bomb’s-worth of heating. What can I say? My niece is worth it. She’s the bomb. I may want to rephrase that.

But wait, there’s more! Notwithstanding the direct heating, if we assume that the fuel was refined from Alberta’s oil sands⁵, these two flights (there and back) will be responsible for releasing almost 122 tonnes of CO₂ in total from mining, drilling, transportation, refining, and burning. And recall what happens to CO₂ when it’s released into the atmosphere. Yes, some of it ends up, at least temporarily, in carbon sinks (e.g. plants, ocean, soil), but much of it stays in the air, overwhelming the ability of the planet to absorb it, as is evident from the continuing and catastrophic rise in atmospheric CO₂ concentrations.

Recall also that, in only a couple of months, the heat trapped by the CO₂ is equal to the heat produced by burning the fuel it came from. In effect that means that every two months, for as long as the CO₂ is in the atmosphere—which we know can be many thousands of years—it’s as if those flights are flying all over again. That’s the actual upshot. I don’t just fly to and from my niece’s wedding once. It’s as if I do it over and over again, about every two months, effectively in perpetuity. Essentially, these two actual flights—from Vancouver to Cancun and back again—have spawned ghost flights, the effect of which will be, in this particular case, to heat the Earth by about a Hiroshima bomb’s-worth of energy every six years, over and over again, for thousands and thousands of years. It’s a giant kaboom, every six years, but without the mushroom cloud, because thankfully this heat is cumulative, not explosive.

Still I might argue in frustration and defiance, as many of us do, it’s just me! And because it’s just me—just one person—it can’t possibly make a difference what I do! This is a weirdly childish defence from someone who must know, surely, that they’re not alone in the world making unique and original choices. About 12 million people fly every day; that’s usually somewhere between 100,000 and 130,000 individual flights (although the global record as of this writing is 153,359 in a single day ⁶). And, at peak times, there are more than 20,000 planes in the sky at once⁷. But, of course, this number accounts for only the 20,000 physical airplanes in the sky today. It doesn’t include all those ghost flights—the phantom planes of every previous flight I’ve ever taken—the ones that are still up there, haunting us all, for generations to come.

And by “haunting” what I actually mean is “heating”—every flight responsible for more and more heat over the coming centuries, with all the misery it brings—the scorched earth, the flooding, the death and disease—gradually making life impossible for my niece, and for everyone else’s nieces besides. I’d have done just as well to ride to the wedding on one of the four horses of the apocalypse.

So the question posed previously, about flying to my niece’s wedding—

“Is it too much to ask?”

—should be rephrased as, “Is it too much to ask of the planet? Is it too much to ask of everyone else—of every single living thing—that ultimately has to pay for my flight?”

Ingrid and Steve Hansen Smythe

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The Flight Perspective Generator

This tool uses test data⁸ to estimate the global heating resulting from a flight.

How many people are flying?

How many flights would you like to model? (e.g. select 2 for a return flight)

Roughly how long a trip are you taking? (Change the value to update the list of matching aircraft.)

? km

On what aircraft are you flying? (Choose one at random if you don’t know or care)

Flight profiles:

Some aircraft models have multiple flight profiles, i.e. different configurations of number of seats, or distance travelled. If more than one is available, you may select a different flight profile to use a different set of test data.

Adjust the test flight's distance (±0% of test data) to match your planned trip more closely:

0 km

How many years into the future do you want to model?

1000 years

Show my assumptions and tweak the variables in the CO₂ Pulse Response Model

Model tuning controls

Since CO₂ in the atmosphere causes global heating (from sunlight getting absorbed by the Earth, then radiated as heat, which then fails to get radiated back out to space because the greenhouse gases capture it), tracking how CO₂ is reduced is effectively the same as tracking how much heat is added by the CO₂ that remains. I’ve read that a Pulse Response Model for CO₂ sequestration includes accounting for three carbon sinks which work at different rates:

• Over years to decades, plants and the upper ocean absorb some CO₂, but as the ocean absorbs CO₂ it becomes more acidic, which is a whole other problem, and plants can only use CO₂ if they also have good growing conditions - enough sunlight and water - and in the end will release the CO₂ back into the atmosphere, unless they get buried somehow;
• over decades to centuries, the deep ocean absorbs some CO₂, but as the ocean warms and deep ocean turnover slows, this will become less efficient over time; and
• over millennia, geological processes react with CO₂ to form minerals. However, a 2023 paper in Nature¹⁰ reports that rock organic carbon oxidation CO₂ release offsets the silicate weathering sink, rivalling or even exceeding the CO₂ drawdown by silicate weathering at the global scale. Therefore, the geological component of the Pulse Response Model may be functionally zero.

I’ve also read that the Bern Simple Climate Model¹¹ used by the IPCC suggests reasonable values as follows:

• an 18.5-year half life for 34% of emissions to be absorbed by plants and the upper ocean,
• a 173-year half life for 26% of emissions to be absorbed by the deep ocean, and
• a 10000- to 100000-year half life for the remainder to be sequestered by geological forces.

I’ve read criticism of the Bern Model, but typically for being too conservative: it’s quite possible that global heating will exceed what I’m showing here.

I freely admit that I am not using a comprehensive climate model. I’m just providing a rough idea of how much heating is to be expected. These graphs calculate the running total amount of heat that will get added to the atmosphere by the CO₂ that remains after these three processes have sequestered some of it. Adjust these values to see how the graphs change.

Fraction of CO₂ absorbed by plants and upper ocean:

34%

Years before half of the above fraction of CO₂ is absorbed by plants and upper ocean:

18.5 years

Fraction of CO₂ absorbed by deep ocean (adjust this fraction by changing the biosphere fraction above or the geological fraction below)

26%

Years before half of the above fraction of CO₂ is absorbed by deep ocean:

173 years

Fraction of CO₂ sequestered by geological processes:

40%

Years before half of the above fraction of CO₂ is sequestered by geological processes:

10000 years

The carbon intensity of a fuel is a measure of the greenhouse gas emissions from the extraction, refining, distribution, and use of the fuel. To help reduce emissions from oil and gas, the Clean Fuel Regulations aim to make gasoline and diesel progressively cleaner over time. The baseline carbon intensity of Canada’s gasoline is 95 gCO₂e/MJ and the baseline carbon intensity of diesel is 93 gCO₂e/MJ, based on 2016 levels.¹² However, the actual range of carbon intensity from Alberta’s oil sands ranges from 92.5 to 126.5 gCO₂e/MJ⁵, which is considerably higher than Canada’s aspirational goal by 2030 of 81 gCO₂e/MJ for gasoline and 79 for diesel. Adjust the carbon intensity of the model:

109.5 gCO₂e/MJ

At what rate does greenhouse-gas-induced heating duplicate the heat originally obtained from burning the fuel? “The time-integrated radiative forcing from CO₂ released upon combustion exceeds the amount of heat released upon combustion after 0.093 years (~34 days), 0.122 years (~45 days), and 0.161 years (~59 days) for coal, oil, and gas, respectively.” ⁴ The source of aviation fuel is oil, but you may adjust this control to favour a coal-dominant or gas-dominant fossil fuel source to model.

Coal Gas

45 days before the heat of combustion is matched by greenhouse-gas-induced heating

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Sources

1 Earth is Heating at a Rate of Over One Million Hiroshima Bombs Every Day! - by Prof. Eliot Jacobson: The Climate Casino, 15 April 2026

2 Joule per kilogram - Jet fuel Jet-A rates MJ/kg, so you can simply multiply the number of kilograms of fuel burned by that number to get the megajoules of heat per flight.

3 Best of Quirks: Listener question show - Quirks and Quarks (CBC) 7 August 2021

4 Time scales and ratios of climate forcing due to thermal versus carbon dioxide emissions from fossil fuels - by Xiaochun Zhang and Ken Caldeira: Geophysical Research Letters, 2 June 2015. N.B.: "The time-integrated radiative forcing from CO₂ released upon combustion exceeds the amount of heat released upon combustion after 0.093 years (~34 days), 0.122 years (~45 days), and 0.161 years (~59 days) for coal, oil, and gas, respectively."

5 Life cycle assessment of greenhouse gas emissions from Canada’s oil sands-derived transportation fuels - by Balwinder Nimana, Christina Canter, and Amit Kumar: Energy, Volume 88, August 2015. Using oil sands to create jet fuel is far less efficient than Canada’s 2030 target of 79.95 gCO₂e/MJ (grams of carbon dioxide produced over the entire life cycle, from mining through processing, transportation, refining, and finally burning). If jet fuel originates from Alberta crude oil, it emits between 92.5 gCO₂e/MJ and 126.5 gCO₂e/MJ.

6 Global Air Travel Had Busiest Day on Record Despite Recent Headwinds - by Amanda Greenwood: Newsweek, 26 July 2026

7 How Many Planes Fly Per Day Around the World? - European Aviation School, Barcelona, 16 June 2025

8 Fuel economy in aircraft - Example Values: Wikipedia, 24 July 2026

9 IATA Carbon Offset Program, 19 April 2022 - The combustion of 1 kilogram (kg) of jet fuel in an aircraft engine produces kg of carbon dioxide (CO₂)

10 Rock organic carbon oxidation CO2 release offsets silicate weathering sink - by Jesse R. Zondervan, Robert G. Hilton, Mathieu Dellinger, Fiona J. Clubb, Tobias Roylands & Mateja Ogrič: Nature, 4 October 2023

11 The Bern Simple Climate Model (BernSCM) v1.0 - European Geosciences Union Geoscientific Model Development: Articles, Volume 11, issue 5, 25 May 2018

12 Secondary Indicator 5.1. Annual lifecycle carbon intensity of gasoline and diesel: Compliance under Canada’s Clean Fuel Regulations - 2025 Progress Report on the 2030 Emissions Reduction Plan, Government of Canada