Carbon offsets have existed for decades, and the size of the voluntary carbon market has ballooned to about $2 billion. Many countries and countless companies, including giants like Amazon and Fedex, use carbon offsets to reduce their emissions as they work toward reaching net zero.
And yet, these offsets haven’t significantly curbed global greenhouse gas emissions. In fact, global emissions are still increasing. As a climate solution, carbon offsets have failed—and according to a new scientific review looking at 25 years of carbon offset research, they’ve failed because they’re riddled with intractable, deep-seated problems that incremental changes won’t be able to solve.
Carbon offsets have long been criticized for their issues, including concerns over greenwashing or double-counting. Multiple studies have found that individual offset projects overestimate their climate benefits. Offsets also don’t always last; trees used as carbon offsets have burned in wildfires, releasing all the carbon they’ve long stored.
Proponents of carbon offsets say such criticisms focus on “a few bad apples.”
“But the problem is, it isn’t really a few bad apples. It’s pretty much all the apples,” says Joseph Romm, a senior research fellow at the Penn Center for Science, Sustainability and the Media, and the lead author on the review of offset research.
25 years of evidence—and issues
Romm and his fellow researchers looked at carbon offset studies spanning more than two decades, and used more than 200 references, including documents from the Intergovernmental Panel on Climate Change.
Carbon offsets are essentially a way for rich polluters—either countries or companies—to finance projects that reduce emissions somewhere else. Then, they claim that project’s emissions reduction for themselves, while continuing to pollute the atmosphere.
Offsets need to be verified, and also “additional”—a term meaning that the project wouldn’t have happened anyway (it only exists, and benefits the climate, because of the offset program). But the idea of additionality is flawed, Romm says.
Take renewable energy projects, which have long been the base of carbon offset projects, and are still the most common offsets today. “We pay someone to do a renewable energy project, and then we say that that has reduced emissions. [But] the thing is, renewables are now the cheapest [energy to build],” Romm says. As the cheapest option, renewable projects likely would be built anyway, so the offset project didn’t really change anything.
Since the carbon market is voluntary, there’s no regulations or oversight. That creates a “race to the bottom,” Romm says, where buyers pay low prices for offset projects. “It’s left the world with the impression that there’s a vast sea of cheap offsets in poor countries,” he says. “It’s just not the reality. It’s why there’s been a reckoning in terms of companies realizing it’s going to take more effort to reduce their emissions.”
Other issues include impermanence (like offset projects burning in wildfires); leakage (when the pollution or logging is simply moved elsewhere, outside of the offset’s boundary); and double counting (when more than one party claims the same carbon credit).
Carbon offsets are a distraction
Essentially, the voluntary carbon market is full of “junk offsets” that don’t really have a climate benefit.
The appeal of offsets is obvious: Without having to change their own behavior or pay a lot of money, countries and companies can claim another entity’s emissions reductions. But the reality isn’t that easy, and offsets are a distraction from the fact that we need to stop burning so many fossil fuels in the first place.
“At the end of the day, this comes down to: Everyone needs to get their own emissions as low as possible,’” Romm says. “There’s no offloading this problem on someone else.”
Actual carbon capture projects, which sequester carbon from the atmosphere, could work as offsets, but those are currently expensive and operate at a small scale. It takes a lot less money and energy to not burn fossil fuels in the first place, than to burn them and then recapture the emissions.
Such criticism of offsets isn’t new. Romm’s review cites 25 years worth of them. This paper also builds on Romm’s publication from 2023, titled “Carbon offsets are unscalable, unjust, and unfixable—and a threat to the Paris Agreement.”
Romm hopes that by putting all this research in one place, and by having a comprehensive look back at the way carbon offsets have failed over the past two decades, it helps people understand the reality.
Leaders of companies or countries always think they can be the one to solve the intractable issues within carbon offsets, Romm says. They say their technology is better, or that they really care about making it work. The review paper counters that notion.
“We wanted to have somewhere someone could go and simply see the compendium of studies and see that people have been warning about this for over two decades,” he says. “Everything they warned about is true. No one’s ever solved these problems.”