We Wish Buying Carbon Offsets for Your Flight Helped. It Doesn’t.

To find out, let’s start with a few calculations. That round-trip flight from Daniel K. Inouye International Airport in Honolulu to John F. Kennedy International Airport in New York City covers 9,952 miles. According to Flight Free USA’s calculator, the average emissions per passenger for such a flight, not accounting for differences in ticketed class or luggage weight, equal 2.9 metric tons of carbon dioxide equivalents—more carbon emitted, by the way, than 2.9 billion other people on this planet will emit in a single year. But the per passenger fee for offsetting that round-trip flight from Honolulu to New York City—just under $20—doesn’t compare to the true environmental and social cost of those 2.9 metric tons of carbon dioxide released into the atmosphere.

How much should it actually cost per passenger to compensate for the damage caused by a flight? First, you have to grapple with the social cost of carbon (SCC). The SCC is an attempt to estimate the economic damages associated with any increase of one additional metric ton of carbon into the atmosphere, including changes in agricultural productivity, human health across the globe, damage to livable habitats, and accompanying ecocide.

Currently, the official federal estimate of the social cost of carbon is $51 per ton.¹ This is a good place to start if you really want to know what you “owe” as you fly from Hawaii to New York and back. Remember, you need to multiply that $51-per-ton price by 2.9 (based on the average emissions per passenger) to reach your final bill: $147.90. But there’s one more wrinkle. What the federal SCC doesn’t account for is a disparity of income throughout regions around the world. An equity rating helps to account for this disparity; this number allows for a fairer distribution of financial responsibility among countries with very different income levels.

The equity-weighted SCC is, for our purposes, the closest number we have currently to what the average American should owe for remediating the environmental impact of one ton of carbon. Weighting carbon this way takes the price up from $51 a ton to about $246 a ton—we used calculations from University of California Santa Cruz’s efforts to equity-weigh the cost of its carbon—which makes the true carbon bill for your round-trip flight jump to $713.40—close to what you’d pay for the ticket itself.

But the equity-weighted SCC is always a rough estimate, because “it’s such a moving target,” says Ellen Vaughan, Water & Climate Action Manager at UC Santa Cruz, who oversaw the university’s work. “As more information comes online, as researchers record the impacts of climate change at a more granular level, this number is just going to continue to grow.”

After I’ve spent hours talking with experts and months poring over climate reporting and studies, the following seems to be the most consistently recommended advice:

• Fly less. Kim Nicholas, a sustainability scientist at Lund University and author of We Can Fix It, a newsletter that helps readers take meaningful climate action, suggests that the first step is to be more aware of our air travel. Sort your flights into those you need to take (such as to see your loved ones) and those you don’t need to take, and prioritize the former. Ask yourself if you can satisfy your need for a different routine or culture without getting on a plane.
• Calculate the equity-weighted carbon cost of the flights you do take, and if you can afford to, donate that amount to a good cause that you’ve vetted yourself.
• Join a mass-transit advocacy organization such as the US High Speed Rail Association. A 2021 study of China’s extensive high-speed rail network estimated that air travel emitted seven times more carbon emissions per passenger per kilometer than rail travel.

What about packing lighter? I’ve seen this advice bubbling up around the internet over the years: Packing lighter reduces your carbon footprint, in theory, by lowering the plane’s load, and thus the amount of fuel needed to keep the plane in the air. The advice doesn’t seem to have expert support or any studies measuring its potential efficacy, and it’s frankly galling to be asked to bring fewer socks while Elon Musk and Kylie Jenner take private flights lasting a handful of minutes. But if you can, then by all means pack a little lighter—it will lighten the plane and possibly your conscience.

This article was edited by Katie Okamoto and Christine Ryan.