So you get an offer to buy a carbon offset. Here are 4 things to know

The next time you buy a plane ticket or get a package delivered, you might see a pop-up on the website: the chance to buy a carbon offset with your purchase.

That offset is basically a promise, says Danny Cullenward, senior fellow at the Kleinman Center at the University of Pennsylvania. A promise that your money is going toward some action that reduces or removes planet-heating pollution.

It could be a promise that someone will protect a forest that would have been cut down. Or a promise that your support for a wind farm actually reduces fossil fuel use. Sometimes companies frame this promise as balancing out the climate impact of your purchase.

But there’s a problem. “Most offsets don't represent what they claim,” says Barbara Haya, director of the Berkeley Carbon Trading Project.

A growing body of research finds most carbon offsets overestimate the amount of planet-heating emissions they reduce, and some don’t reduce emissions at all.

Recent reports detailing problems with carbon offsets have made many buyers more wary. Last year offset prices tumbled, and the market shrank more than 61%, according to one report.

Looking to improve the offset industry, the U.S. government recently announced standards for “high-integrity” carbon offsets — that is, offsets that actually reduce or remove climate pollution. But researchers say the standards aren’t enough for consumers to know if an offset purchase has a meaningful and lasting impact on the climate.

In California, a bill that would have extended more consumer protections to offset buyers was recently pulled after fierce opposition from the offset industry.

Here are four things to know about what’s going on with carbon offsets.

There are big problems with the quality of carbon offsets

Cullenward says there are lots of “false promises” made by sellers of carbon offsets, sometimes called carbon credits, and two big overarching problems.

First, let’s say you buy offsets from a project that claims it saved a forest from deforestation. Research finds many such projects get money for forests that don't actually need protection, meaning they don’t have the climate benefits they claim.

Other offset project types also routinely overestimate their climate impact, including projects that claim to reduce fossil fuel use, and projects that reduce pollution from cookstoves.

The second big problem with offsets is something called “permanence.” Carbon offsets claim to reduce or remove carbon dioxide — pollution that contributes to warming for thousands of years, even tens of thousands of years.

But most offsets only promise that they reduce or store carbon dioxide for 100 years or less, Haya says. The Integrity Council for the Voluntary Carbon Market (ICVCM), a nonprofit that has a global standard for high-quality carbon credit projects, only currently requires those projects to reduce or store carbon dioxide for 40 years.

“We believe that, logically, that [number] should be increased,” says Annette Nazareth, chair of ICVCM. “Our goal is to raise that bar to perhaps something like a hundred years.”

But whether offsets promise to reduce carbon dioxide for 40 years or 100 years, that doesn’t compare to the effectively permanent impacts of CO2, says Gilles Dufrasne, policy officer at the Belgian nonprofit Carbon Market Watch.

“The scientific fact is that CO2 is going to stay in the atmosphere for thousands of years,” he says.

There are big problems with how offsets are used

Carbon offsets proponents say they deliver important funding for projects that help the environment, local communities, and the climate. But even if an offset project mostly does what it promises, researchers say there are still problems with how consumers use offsets.

Back in the 1990s, some companies envisioned using offsets to fight global warming this way: companies could pay to reduce climate pollution somewhere else, and thereby cancel out the effects of the climate pollution they caused.

That thinking is flawed, says Mark Kenber, executive director of VCMI, a nonprofit that helps businesses and governments navigate the offset market.

“Companies and to a certain extent individuals [have] been misled to believe that, ‘Oh, I'm having no impact on the climate because I bought a bunch of cheap carbon offsets.’ And that's clearly not the case,” Kenber says.

The proper way to use offsets, according to Kenber, is for a company to first reduce as much planet-heating pollution in its supply chains as possible, and then buy offsets to make up for what it can’t reduce. Only then, he says, should a company claim it’s properly using offsets to meet climate targets. (He argues individuals should similarly reduce their emissions even if buying offsets.)

But Cullenward says there’s a complication: “There's very little evidence to suggest that that's actually how people are using those offsets.”

Cullenward says many companies and consumers still use offsets the way they were originally conceived – as if offsets can actually cancel out their pollution, which they don’t.

Offsets have long been used to signal green credentials, says Jessica Green, professor of political science at University of Toronto. “Offsets have always been a way to manage brand reputation,” she writes in an email.

But because offsets are often framed as a bigger climate solution than they actually are, critics say they can delay and distract from more meaningful emission reductions. This month more than 80 nonprofits including Amnesty International and Oxfam wrote a statement calling for companies to stop using carbon offsets, arguing they undermine climate action.

There are problems with a new government effort on offsets

In late May Treasury Secretary Janet Yellen announced new principles for better quality carbon offsets. The principles say that climate pollution reduced or removed by offset projects should be “real and quantifiable.”

Ethan Zindler, climate counselor at the Treasury Department, also says the principles are clear that before buying offsets, “priority 1 for corporations should be to decarbonize their own emissions first.”

But researchers say even this new government effort has gaps. One, the principles are voluntary and not backed up by law or federal regulations. Also, the principles don’t spell out how long carbon offsets should keep climate pollution out of the atmosphere.

“How long do the principles say the offsets have to keep pollution out of the atmosphere?” Cullenward asks, “‘For a specified period of time’. That is not a principle. That is hand waving.”

Zindler says that while “we don't set a specific year in the guidance,” he notes that as technologies continue to develop – like projects that suck carbon dioxide out of the atmosphere and store it – carbon offsets will become more permanent in the fight against climate change.

So far, this kind of more permanent carbon removal technology represents a small percent of the offset market. As for the voluntary nature of the principles, Zindler says in an email they are “an important step forward” and that other parts of the government are currently developing regulations and enforcement measures.

A California state senator tried to fight the offset industry, and lost

For an offset buyer who wants to know they’re getting what they pay for, the answer isn’t voluntary principles but laws against false advertising, says Monique Limón, California state senator.

That’s why Limón authored a bill in the California state senate that would have required that offset companies be accurate in their marketing statements. Here’s how Limón described the bill to NPR in May: “If that [carbon offset] company knows that I'm not getting what I paid for, and you paid for it, you can take them to court.”

The bill faced backlash largely from the offset industry, including groups with ties to the fossil fuel industry. And while some environmental groups supported the bill, others with connections to carbon offsets opposed the bill as it was written.

Late last month, Limón withdrew the bill. Limón told NPR that while she had the votes necessary on the assembly floor, she didn’t think it would make it past the desk of California Gov. Gavin Newsom. Last year Newsom vetoed an earlier draft of the bill arguing it could “inadvertently” hurt “well-intentioned” players in the offset market.

When asked for comment about the latest bill, Newsom’s office referred NPR to his earlier veto.

Limón says the offset industry’s resistance to this bill should be instructive for consumers thinking of buying offsets.

“I do feel that this is eye-opening for consumers,” Limón says. “Why does a market push so hard against having legally enforceable standards?”

So, what should people do when that offset pop-up appears on their screens? Haya says for now it’s still too difficult for regular consumers to know if most offsets are legitimate. “I would say if you were offered offset credits when you buy a plane ticket or whatever, don't buy that credit,” she says.

“If you're going to spend money, spend money on reducing your own emissions,” Haya says. “And then if you want to do more than that, donate to a [climate] organization.”