What do cows and airplanes have in common?

Much more than you wanted to know

Like any stereotypical mixed vegan vegetarian in their early twenties, I was thinking about my environmental impact yesterday.
The most immediate source was that I had purchased tickets a few weeks ago to go home for thanksgiving. United provided emissions numbers, which were

1. not small (>600kg CO2 round trip)

2. still much smaller than other estimates I had seen, most recently from Wren¹
   Wren estimates that this trip costs more than a metric ton of emissions per leg. That is an almost 3x difference. What gives?

CO2 emissions vs global warming

These are not the same thing. I always knew this from discussions of cows burping² but CO2 is in some sense a lightweight greenhouse gas: we just emit a lot of it. Methane and Nitrous Oxide are far more effective at trapping heat³. Cows produce a lot of methane, and planes produce both. Unfortunately, we don't know exactly how much because these things are difficult to measure. This has not stopped people from trying to estimate the net effect of plane travel at somewhere between 2-4 times worse than the raw CO2 emissions⁴. This ratio, called the Radiative Forcing Index (RFI), explains the discrepancy cleanly. Yay?

Two tons is a lot of CO2

Do you remember seeing this graphic from The Guardian, showing how the emissions of your flights compare to the yearly emissions of some countries?

That statistic doesn't take the RFI into account. What is your cross country plane trip actually emitting?

My plane trip to see my grandparents in India warms the planet more than:

1. Their respective years of emissions combined

2. the average citizen of Denmark does in a year

Lets say I wanted to offset this. How much would it cost?

Offsets and DAC

Roughly speaking, there are three different ways you can try to offset your carbon footprint:

1. Carbon offsets that meet the legal definition but not much else. I found some here for $3-6 a ton

2. Carbon offsets that put in the legwork to verify their contributions. I use Wren (not an ad) for this, and they quote the cost of their offsets here as being $18 a ton in 2021 and $25 a ton in 2022, growth driven in large part for larger demand for high quality carbon offsets.

3. Direct air capture. This currently varies between $250 and $600 dollars per ton. The estimates for the plants building today are roughly half that at between $125 and $300 a ton. The International Energy Agency also estimates that there is a possibility costs fall below $100 a ton by 2030.

Lets say I wanted to bake in the emissions cost of the flight into the monetary cost of my ticket. How much of a price increase would that be?

This roundtrip costs ~$500-600 on peak days and $300 on the cheapest days. Offsets for it would cost ~$10, $50, and $500 from each of our three sources, representing a 2%/10%/100% increase in cost.

Is that less than you expected?

At current levels of demand, its not that expensive for your existence to have a net neutral impact on global warming. Using Wren prices, it costs $500 a year for the average American. Your market demands' impacts on the environment wash each other out.
I don't want to equate this with being "net neutral", for two reasons⁵.
First, these calculations are heavily predicated on a world where only a fraction of a percent of people (and next to no corporations) care enough to pay off their emissions. This low demand makes prices cheaper: in a world where countries had to actually decrease emissions demand would soar and prices for both carbon offsets and general goods would rise considerably. People who work to decrease their own impact would suffer much less than the general populace.
Second, I have historically benefited enormously from my high emissions lifestyle. The goal should be to ensure that future generations are able to have an equal or better quality of life, and in this sense being "net neutral" ceases to make sense on an individual level.

Well, that's more than what you wanted to know about offsetting your airplane emissions. I need to get back to research.

1. #NotAnAd but Wren is the combination of modern day indulgences with an effective charity organization. See later in the post for details

2. As an aspiring vegan who has a hard cap on the number of non dairy meals per week I am contractually obligated to say this:

(first graph is from here, second is from here)
Cows produce more emissions than all planes and ships combined.
If your cope is that these two graphs diverge in how big the livestock section of the chart is, understand this: most of the crops we make aren't eaten by humans. The food pyramid is an unfortunate reality: if you get even a sizable chunk of your energy from animals, you require a mountain of feed for them to chew on shackled in their own feces.

3. fun fact there are pollutants that decrease global warming. The most common of these is sulfur dioxide, often produced when burning some fossil fuels or extracting copper. The problem is that sulfur dioxide also breaks down the ozone layer and causes sulfuric acid to fall from the sky. Hopefully someone will figure out a compound that doesn't cause massive environmental damage and has this effect.

4. See here and here for more discussion

5. Ok, three. As much as I gush about Wren, 75% of their current costs are being paid with investor money. On the other hand, half of their expenses are marketing. Right now, 80% of funds go to climate opportunities, where if investor cashflow was cut off roughly 55% would. This would reflect a 45% increase in the cost of offsets, which would roughly get you to $36 a ton.