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. 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.”
