Taylor Swift may not be the first person who comes to mind when you think about climate change. But more than once, the singer has found herself in the middle of a media storm over her carbon di­oxide emissions. Swift regularly hops aboard her private jet, as she did in 2024 to get from a concert in Tokyo to the Super Bowl in Las Vegas the next day. A spokesperson said that Swift purchases more than enough carbon credits to offset her jet-setting. But fans and haters alike want to know: Is it enough? 

If you travel by plane, even in less-glamorous economy, you’ve probably faced a similar question. Airlines often offer passengers the option to pay a few extra dollars to offset their share of the flight’s emissions. It’s considered the climate-friendly thing to do. By purchasing carbon credits, you’re paying someone somewhere to take some action — probably saving an existing forest or perhaps planting trees — that reduces total global emissions enough to cover your contribution. You can take off without a guilty conscience. Supposedly.

Over the last few years, though, carbon credits have faced increasing scrutiny. A string of academic studies and media investigations have concluded that many credits do not represent genuine emissions savings. One investigation concluded that over 90 percent of carbon credits issued for rainforest protection by the largest carbon credit certification body “had no benefit to the climate.” Two reports published in 2023 found that credits for forest-based projects in North America, South America, Africa and Asia may in fact increase net emissions. 

That same year, uncertainty over the validity of credits caused the voluntary carbon market to collapse; the market’s value dropped by more than 60 percent. Given the current situation, “it’s nearly impossible to be certain that what you’re buying is high integrity,” says Stephen Lezak, a researcher at the Berkeley Carbon Trading Project at the University of California, Berkeley. 

Amid all the controversy, it’s not clear what a consumer (celebrity or not) should do. To buy or not to buy? But understanding what carbon credits are, how they work and why the system has gone wrong can help.

What are carbon credits? 

As concern over climate change has grown, governments, companies, organizations and individuals have sought ways to reduce greenhouse gas emissions to keep the global average temperature to no more than 1.5 degrees Celsius above preindustrial levels. Many are working toward net-zero goals, meaning that at some point in the future — by 2050 at the latest — any CO₂ emitted must be counterbalanced by eliminating emissions elsewhere or taking CO₂ out of the atmosphere. 

Achieving net zero should begin with every effort to eliminate or reduce the burning of fossil fuels, the main cause of global warming, says Kaya Axelsson, head of policy and partnerships at Oxford Net Zero, a research program at the University of Oxford.

Offsetting via carbon credits is another way to balance the carbon checkbook. The idea first took hold in the 1980s and picked up in the following decade. Industrialized countries that ratified the 1997 Kyoto Protocol became part of a mandatory compliance market, in which a cap-and-trade system limited the quantity of greenhouse gases those countries could emit. An industrialized country emitting over its cap could purchase credits from another industrialized country that emitted less than its quota. Emitters could also offset CO₂ by investing in projects that reduced emissions in developing countries, which were not required to have targets.

“The atmosphere doesn’t care where the emissions reductions happen,” says Barbara Haya, director of the Berkeley Carbon Trading Project.

The United States, which did not ratify the Kyoto Protocol, is not part of any compliance market, but such markets exist within the country. California’s cap-and-trade program, for one, requires the participation of about 450 businesses responsible for about 85 percent of the state’s greenhouse gas emissions.

According to the United Nations, countries’ commitments are falling short of what’s needed to reign in rising temperatures. And President Donald Trump withdrew the United States from the 2015 Paris Agreement, which superseded the Kyoto Protocol. The voluntary carbon market offers a private sector alternative to compliance markets. 

Demand for a voluntary market took off in the early 2010s as more companies took on net-zero goals for public relations or ethical reasons, or both. One carbon credit represents one metric ton of CO₂, either removed from the atmosphere or not emitted in the first place. Since the voluntary market’s inception, some 2 billion carbon credits have been issued, equivalent to about 5 percent of global annual emissions.

Offsetting is often cheaper than reducing, especially in cases where emissions-free options aren’t readily available, such as with jet fuel in the airline industry. If the cost to directly abate one ton of emissions is $1,000, but a company can buy a credit for much less, offsetting may make more sense, and cents.

Credits for removing CO₂ are usually straightforward, Lezak says. Whether it’s sucked from the air and stored underground or stashed in coastlines through mangrove restoration, “you can usually point to it [and] say, I took it out of the atmosphere,” he says.

But according to the Berkeley Carbon Trading Project’s Voluntary Registry Offsets Database, only about 4 percent of carbon credits in the voluntary market come from pure removals projects. The other 96 percent come from projects that claim to reduce or avoid emissions. They might limit methane released from landfills or swap solar panels in for fossil fuel–based power. The largest component of credits comes from avoided deforestation, in which forests that probably would have been felled are instead preserved.

How are carbon credits issued?

A carbon project involving forests typically begins with a landowner who is interested in taking some offsetting action. Perhaps a farmer decides not to cut down a patch of trees for agriculture. A project developer helps the landowner turn that offsetting action into carbon credits that compensate the farmer for the lack of produce — and profit. The developer works through a carbon credit certification body that’s responsible for verifying the project and issuing credits. Such organizations have methodologies for calculating how much carbon will be stored and converting that amount into carbon credits.

After the project is implemented, the developer hires a third-party auditor approved by the certification body to sign off on the project. Only after this independent look will the certification body issue credits.

“It’s nearly impossible to be certain
that what you’re buying is high
integrity.”

Stephen Lezak
a researcher at the Berkeley Carbon Trading Project

From there, the developer will often partner with a broker to find buyers. Brokers work on commission or buy credits from the developer and try to sell them at a profit. 

Carbon credits can be bought, sold and bundled in complicated ways before they’re ever used to offset emissions, Lezak says. That’s the final step in the process — retiring a credit — at which point it can no longer be bought and sold. Most often, when a credit is retired, it’s used to offset emissions generated from a carbon-intensive activity, like flying. But a credit can also be retired without any actual offsetting. 

By bundling credits that haven’t been retired and selling them in packages, brokers hedge against the reality that many credits may be of low quality, Lezak says. “The pooling mechanism gives the appearance of some protection against those risks.” Yet projects that go through the certification process may suffer from overcrediting, promising more emissions reductions than they can actually achieve. 

The problem of additionality

For a carbon credit to be issued, emissions reductions must be additional, meaning those greenhouse gases would have been emitted if the project didn’t exist. If a landowner never planned to cut down a forest to begin with, the purported reductions are nonadditional. 

Correctly calculating additionality requires accurately determining the baseline, business-as-usual scenario, says Alexander Shenkin, a forest ecosystem ecologist at Northern Arizona University in Flagstaff. But when baselines are incorrectly calculated, they usually result in too many credits being issued. A study published in 2023 in Science, for example, found that incorrect baselines led to carbon credits issued in the Democratic Republic of the Congo, Tanzania and Zambia with no evidence of avoided deforestation. Forests were not at risk of being cut down, so the projects were nonadditional.

Some projects, Axelsson says, “sell four or five credits for every one ton of carbon.” When a business, country or individual uses meaningless credits to counterbalance their emissions, they are not achieving neutrality.

In a now famous example of overcrediting reported in the New Yorker, a company hired to sell credits for a project in Zimbabwe originally calculated that the project would keep about 50 million tons of CO₂ from the atmosphere. But after implementing an approved methodology, that number jumped to some 200 million credits to be issued over the course of the project. The project was paused before all credits could be issued, but by at least one estimate, the project had 30 times as many credits as it should have based on actual emissions savings. 

Excess credits undercut the price of legitimate ones, according to a paper published in 2020 in the Proceedings of the National Academy of Sciences. When demand was high for carbon credits, as it was before 2023, the price per credit should have been high. But with a large supply of poor-quality credits flooding the market, the price stayed relatively low. 

According to S&P Global, the price of nature-based avoidance credits went from $11.50 per ton of CO₂ to just $3.50 over the course of 2023. In contrast, technological carbon capture credits hovered around $120 per ton of CO₂.

Third-party auditors can’t do much to improve projects, says former auditor Thales West, a forest scientist at Vrije Universiteit Amsterdam and lead author of the papers in Science and PNAS. “All I’m doing is checking the boxes that are related to the rules.… I wouldn’t have the power to say: You’re not going to get the certification.” 

More credits mean more money for the developer. Plus, the certification body gets paid per credit issued, so there’s an incentive to issue more credits. And because the developer pays the auditor, “there is a financial incentive for the auditor to sign off,” says Elias Ayrey, cofounder of Renoster, a start-up that independently scores the quality of carbon projects.

If an auditor approves a project, they’re more likely to get hired again, says Libby Blanchard, a political ecologist at the University of Utah in Salt Lake City. “If there’s some way to make the auditing process more independent and less tied to the outcome that the auditor provides, we would have a much better and transparent market.” 

Problems of leakage and permanence

Another dilemma is that carbon credits often ignore the interconnectedness of the world; actions in one place affect what happens elsewhere. If a rancher chooses not to turn forest into lucrative cattle-grazing land, that action is additional and seems to be deserving of carbon credits. But if the demand for the beef remains, deforestation might just happen elsewhere.

“Leakage happens when supply is restricted, but demand is unchanged,” Lezak says. An article in Climate Policy in 2021 illustrates the point. Deforestation shifted from Brazil’s Amazon to the less-regulated Cerrado — an incredibly biodiverse tropical savanna — after Brazil adopted the Amazon Soy Moratorium. Under the moratorium, established in 2006, soybean traders agreed not to purchase soy grown from newly deforested Amazon lands. However, the moratorium led to a 31 percent increase in soy production in the Cerrado. Deforestation there rose by an estimated 13 percent. 

Carbon projects, Lezak says, should be additional while also decreasing demand. Providing someone who cooks over an open fire with a fuel-efficient cookstove, for example, reduces emissions thanks to the increased energy efficiency. It also reduces local demand for wood, meaning less deforestation, without shifting demand elsewhere.

But even those projects may result in overcrediting, depending on how the emissions savings are calculated and how long and often the cookstoves are used. Because a project in Mozambique used stoves that couldn’t withstand rain, for instance, the stoves were largely abandoned earlier than expected.

Issues of permanence — project longevity — can also plague forest projects. Though they are designed to store carbon for a century, the projects are prone to wildfires, disease and illegal logging. “If that forest doesn’t last for 100 years,” Blanchard says, “that carbon was only temporarily sequestered.” 

Developers are supposed to check on the forests every five years or so. “But if something has gone terribly wrong,” Ayrey says, “the developer isn’t going … to report that.” The result: “zombie” credits from failed projects that are used for offsetting. 

The major certification bodies require some portion of credits issued for each carbon project be set aside and held in a buffer pool to function as a kind of insurance in case of catastrophe.

But buffer pools may be too small, as demonstrated in a 2022 study in Frontiers in Forests and Global Change. Looking at California’s forest carbon offsets, researchers found that wildfires had depleted nearly one-fifth of the buffer pool in less than a decade. When also accounting for disease, the scientists concluded that the buffer pool isn’t likely to guarantee the integrity of California’s offsets program for the requisite century. Plus, because greenhouses gases can last in the atmosphere for thousands of years, some experts argue that the century standard is not long enough anyway. 

How to improve the voluntary carbon market 

Government regulation of the voluntary carbon market could help ensure that carbon credits meet a standard quality, Ayrey says.

Regulation could also help with transparency. Each certification body has its own registry. “You know what credits have been issued, and then the next thing you know is who’s retired them, but you don’t know how many times the credits were bought and sold, and by whom,” Haya says. Along the way, she says, “you don’t know anything about prices.”

In September, the U.S. Commodity Futures Trading Commission adopted its first guidelines for the voluntary carbon market. Though guidelines do not have the same leverage as regulations, the guidelines were instrumental in bringing fraud charges against the U.S.-based developers of the Mozambique cookstove project. However, it is unclear how much of a role the government will play in more rigorously regulating the market. 

For forest projects, remote-sensing technologies, which can quickly image forests in and around projects to better determine baselines, could improve transparency. Because monitoring can be monthly, weekly or even daily, satellites can also keep an eye out for leakage and permanence problems.

Independent companies that rate carbon credits are springing up to do this kind of eyes-in-the-sky work. Buyers looking to purchase high-quality credits can pay start-ups like Renoster to assess projects. 

“The atmosphere doesn’t care where the emissions reductions happen.”

Barbara Haya
director of the Berkeley Carbon Trading Project

Some companies have stopped bothering with offsetting and started focusing on reducing the emissions they can control. These companies don’t want to buy low-quality credits, Lezak says. They also don’t want the PR backlash — or even lawsuits — that can come with false claims of neutrality, Shenkin notes.

Blanchard and colleagues argued last year in One Earth that credits based on emissions offsets is not a good system. Participants need to recognize that, in the market’s current state, “we’re not truly reducing our emissions,” Blanchard says.

The researchers envision a framework in which offset projects are reframed as climate mitigation projects. Companies or individuals may buy carbon credits or otherwise donate to projects. But “instead of claiming that you’re offsetting your emissions, you’re claiming that you’re contributing to global climate mitigation,” Blanchard says.

This scheme would eliminate the need for brokers and other middlemen. And it would preserve many of the co-benefits that stem from some of these projects. Many forest projects, for example, double as conservation efforts that maintain air quality and biodiversity. Some projects, Ayrey says, also return some revenue to people who live in or near the forests. 

Because funding is coming mostly from industrialized countries, the carbon market can bring in conservation funds to developing countries.

Without the market, “there’s one fewer way that we have to conserve these forests,” Shenkin says.

Ultimately, though, the market must shift toward removal-based technologies, Axelsson says, and encourage investment in new technologies for carbon capture and long-term storage.

So, should you buy carbon credits to offset airlines emissions? 

When it comes to buying carbon credits through an airline, Axelsson says she sometimes clicks “yes” as a signal that people do care about climate change — and demand action. “But I click ‘yes’ knowing that that’s not an offset,” she says. 

Another option is to estimate your emissions and support carbon projects on your own. An internet search will often reveal scandals, Ayrey says, and thus projects to avoid. Renoster also makes its reports public.

You can also vet companies based on whether they’re moving toward mitigation strategies that reduce their carbon footprint. The Science Based Targets initiative dashboard captures what companies around the world have pledged to do. 

In the end, if individuals want to reduce their carbon footprints, changing behavior will have a bigger impact than buying carbon credits, West argues. “You have to fly less, consume less meat, use bikes more.” 

Blanchard agrees. Permanently reducing your emissions, she says, “is way more meaningful.”