America's wealthiest people are also some of the world's biggest polluters -- not only because of their massive homes and private jets, but because of the fossil fuels generated by the companies they invest their money in.
A new study published Thursday in the journal PLOS Climate found the wealthiest 10% of Americans are responsible for almost half of planet-heating pollution in the US, and called on governments to shift away from "regressive" taxes on the carbon-intensity of what people buy and focus on taxing climate-polluting investments instead.
"Global warming can be this huge, overwhelming, nebulous thing happening in the world and you feel like you've got no agency over it. You kind of know that you're contributing to it in some way, but it's really not clear or quantifiable," said Jared Starr, a sustainability scientist at the University of Massachusetts Amherst and a report author.
This study helps build a clearer picture of individual responsibility by going beyond what people consume, he told CNN.
To do this, the researchers analyzed huge datasets spanning 30 years to connect financial transactions to carbon pollution.
They looked at the planet-heating pollution produced by companies' direct operations, as well as those relating to companies' climate impacts further down the supply chain -- for example, the bulk of an oil company's emissions comes when its customers burn the oil it extracts.
That gave a carbon footprint for each dollar of economic activity in the US, which the researchers linked to households using population survey data that showed the industries people work for and their income from wages and investments.
They found the wealthiest 10% in the US, households making more than about $178,000, were responsible for 40% of the nation's human-caused, planet-heating pollution. The income of the top 1% alone -- households making more than $550,000 -- was linked to 15% to 17% of this pollution.
The report also identified "super-emitters." They are almost exclusively among the wealthiest top 0.1% of Americans, concentrated in industries such as finance, insurance and mining, and produce around 3,000 tons of carbon pollution a year. To put that in perspective, it's estimated people should limit their carbon footprint to around 2.3 tons a year to tackle climate change.
"Fifteen days of income for a top 0.1% household generates as much carbon pollution as a lifetime of income for a household in the bottom 10%," Starr said.
Climate impact is not just about the size of the people's income but the industries that generate it. A household making $980,000 from certain fossil fuel industries, for example, would be considered a super-emitter, according to the report. But a household making money from the hospital industry would need to bring in $11 million to produce the same amount of planet-heating pollution.
The report's authors call on policymakers to rethink how they use taxes to tackle the climate crisis.
Carbon taxes that focus on what people buy -- the food we eat, the cars we drive, the clothes we buy -- "disproportionately punish the poor while having little impact on the extremely wealthy," said Starr. They also miss the chunk of wealth rich people spend on investments rather than buying things.
Governments instead should focus on taxes that target shareholders and carbon-intensive investments, the report said. Although it will be "a hard political ask," Starr acknowledged, especially as the wealthiest tend to have disproportionate political power.
Many ideas for taxing carbon have been floated around the world including windfall taxes on fossil fuel companies and wealth taxes, but few have been politically viable.
Kimberly Nicholas, associate professor of sustainability science at Lund University in Sweden, who was not involved in the report, said the study helps reveal how closely income, especially from investments, is tied to planet-heating pollution.
Sometimes when people talk about ways to tackle the climate crisis, they bring up population control, said Mark Paul, a political economist at Rutgers University who was also not involved in the study. But studies like this "shine light on the outsized responsibility that the rich have in generating and perpetuating the climate crisis," he told CNN.
Identifying the main actors behind the climate crisis is vital for governments to develop policies that cut planet-heating pollution in a fair way, he added. Although he disagreed with the study's assertion that carbon taxes on consumption disproportionately affect the poor, saying there were ways to implement them fairly.
The outsized climate impact of the rich is, of course, far from just a US problem.
Globally, the planet-heating pollution produced by billionaires is a million times higher than the average person outside the world's wealthiest 10%, according to a report last year from the nonprofit Oxfam.
"At the moment, the way the economy works is that it takes money and turns it into climate pollution that is destabilizing life on Earth," Nicholas said. "And that fundamentally has to change."
