Look at the person to your left. Now, look at the person to your right. Congratulations! The three of you just murdered somebody. That is, assuming you’re American. If you’re from Brazil, you’ll need to find 24 others to help you take a life. If you’re in Nigeria, good luck: it’ll take 146 of you.
What are we talking about? Well, an analysis published this week in the journal Nature Communications has taken a look at the “mortality cost of carbon” – that is, how many lives will be lost as a result of the world’s carbon usage – and the results are stark. For every 4,434 metric tons of CO2 over the 2020 rate of emissions – that’s the equivalent to the lifetime emissions of about 3.5 Americans – one person dies.
Now, despite the bombastic lede, this shouldn’t actually be read as saying that each individual American will kill one-third of a person in their lifetime. What it means is that, with emission levels as they are, the lifetime carbon footprint of one American corresponds to 0.29 of the human deaths from climate change over the next century.
You may have noticed we’ve mostly been talking about the estimates for the US. The “average” person worldwide produces about one-fourth the amount of carbon emissions in their lifetime as an American; as we mentioned earlier, the lifetime carbon emissions from one Brazilian is enough to kill just 0.04 people – one-seventh the amount of human an American can kill. In Nigeria, the lifetime kill count is even lower, at 0.01. Just five countries came out looking worse than the USA: Saudi Arabia, Qatar, Kuwait, the United Arab Emirates, and Australia.
“There are a significant number of lives that can be saved if you pursue climate policies that are more aggressive than the business as usual scenario,” study author Daniel Bressler told The Guardian. “I was surprised at how large the number of deaths are. There is some uncertainty over this, the number could be lower but it could also be a lot higher.”
That uncertainty is due to a number of factors. For one thing, Bressler’s estimates are based on several key studies, each of which came with their own error ranges. His conclusions were therefore based on the central estimates from these studies.
For another thing, Bressler’s study only accounts for deaths due to rising temperature. This was a purposeful choice, the study notes, as it contrasts with the trope of “climate change ftw” that recently got the BBC in so much trouble. However, it means that the study ignores deaths from other climate crisis-related phenomena, such as war, wet weather extremes, sickness and malnutrition, air pollution, or food shortages (to name a few).
Bressler’s study can be seen as a reformation of the “social cost of carbon”, a complex economic metric that “prices” carbon emissions based on the damage it is projected to inflict in the future. Governments use this figure to decide environmental policy: simplistically put, if the cost of adaptation to reduce emissions is more than dollar amount that those same carbon emissions would inflict, then the adaptations are considered a waste of money. The concept earned its inventor, William Nordhaus, a Nobel prize, but Bressler says his figures needed an update.
“Nordhaus came up with a fantastic model,” he told The Guardian, “but he didn’t take in the latest literature on climate change’s damage upon mortality, there’s been an explosion of research on that topic in recent years.”
Bressler’s new estimate drives the cost of carbon up steeply: from $37 per metric ton to $258. That means the world needs to take drastic action – ideally reaching full decarbonization by 2050. By his calculations, Bressler says, that would save 74 million lives over the next century.
“Our emissions are very much a function of the technology and culture of the place that we live,” said Bressler. “[We need] large-scale policies such as carbon pricing, cap and trade, and investments in low-carbon technologies and energy storage.”