Last month, Bernie Sanders’ presidential campaign made a minor splash when it announced it would offset all carbon emissions caused by traveling. “[W]e know we need to address our emissions through action, not just rhetoric,” campaign manager Faiz Shakir said in a statement. Carbon offsetting—the practice of investing in green technology or planting trees as a means of counterbalancing one’s carbon footprint—has been a popular climate mitigation strategy since the late ’90s. Leonardo DiCaprio does it. So does Jake Gyllenhaal. Al Gore too. It’s a trendy strategy, one that offers good optics and, yes, genuinely can help remove carbon from the atmosphere.

It also further highlights just how awful presidential campaigns are for the Earth in the first place.

In a country as large as the United States, the campaign trail can become Odyssean in scope. In a crude analysis of the 2016 presidential election, The Boston Globe estimated that both Hillary Clinton and Donald Trump traveled more than 200,000 miles from the start of their campaigns in 2015 to October 2016 (right before the election). That’s enough mileage to cross the continental U.S. 75 times over.

Doing the math to calculate the carbon footprint in previous campaigns is tricky with the available data. A 2013 study in Environmental Science and Technology estimated that a domestic jet flight can produce anywhere between 28,175 and 32,715 grams of CO2 per mile. A “large gasoline car” on the other hand produces 438 grams of CO2 per mile. Calculating the carbon cost of all that travel would require a breakdown of what percentage was done by plane, car, bus, and train, and how many other passengers were aboard the vehicle. These data are not available, but it’s safe to assume flying accounts for the majority of the mileage.

“There’s no doubt that flights account for upwards of 85 percent of these candidates’ travel,” says one Democratic Party staffer who asked to remain anonymous for fear of admonishment. “No early states strategy will have a candidate driving around Iowa for a month in a Prius.” Even just using crude estimation to set some upper and lower bounds, it’s easy to see the massive footprint a campaign leaves on the environment.

In an extremely conservative scenario: If only half of the candidates’ total mileage came from flying (100,000) each would have produced 3,600 tons of CO2 in aviation emissions. If they flew economy on a commercial airline on a 400-seat plane for each flight, that would come out to 90 tons of CO2 just from airline travel.

For a more liberal analysis: If 90 percent of the candidates mileage came from flying (180,000) each would’ve produced 6,500 tons of CO2 in aviation emissions. If they flew business class on a commercial airline with 100 seats on the plane, that would come out to 130 tons of CO2 per person from airline travel. And if they flew on private jets exclusively, with a staff and crew of say, 20, that number jumps to 325 tons per person just from airline travel.

The average American, by contrast, produces about 40 tons of CO2 in a two-year span (and that’s counting all aspects of life—not just flying). Campaigning for the presidency is anything but Earth-friendly.

As of now, there are 17 confirmed Democratic candidates for 2020; nearly all of them are running on a green, or greenish, platform. So far, Sanders is the only candidate to put forward a mitigation plan for his campaign travel, but others might be wise to follow suit, says Democratic strategist Tara Dowdell. “I think this is part of a larger trend where you have the base of the Democratic Party saying it’s not enough that you’re not Trump or you’re not a Republican,” she says. “We need to be, as a party, better. We need to be demonstrably better.”

The appeal of carbon offsets is tied to their relatively low cost. It’s much less expensive to remove a ton of carbon from the air in the future than it is to pay for the damage that emitting a ton of carbon causes. Calculating the damage to society from a ton of CO2 emissions is a difficult task. Groups, such as the Environmental Defense Fund, have estimated the social cost of carbon emission are around $40 per ton. Other researchers calculate the number to be closer to $220 per ton.

“The problem is that it’s being used to kill any more ambitious ideas.”

“It’s much better than doing nothing,” says Jens Borken-Kleefeld, a senior researcher at the International Institute for Applied Systems Analysis, a scientific research nonprofit. “The best option is of course preventing these damages in the first place—but that’s hard when you’re traveling.”

Borken-Kleefeld is not the only scientist concerned that offsets provide a lesser means of climate retribution—one that still fails to address the crux of the issue. “It’s great that [Sanders] is recognizing that aviation emissions are bad for the environment and they need to be addressed,” says Bill Hemmings, the director of aviation and shipping at the nonprofit Transport and Environment. “The question is, to what extent is offsetting the way to do it? It doesn’t do anything about aviation emissions. The problem is that it’s being used to kill any more ambitious ideas.”

Hemmings is concerned that carbon offsetting will be used as a way of shirking the real, difficult question of how to actually reduce airline emissions. “The damage you’re doing can never be compensated,” says Borken-Kleefeld. “If you’re hurt and get a compensation in terms of money, that is never equivalent to being un-hurt.”

To be fair, much of Sanders’ campaign is built around decarbonizing the economy; the senator would probably love to reduce airline emissions to zero if he could, but such a measure would be a) extraordinarily expensive and b) politically ineffectual. And while there do exist methods of reducing airline emissions, none of them come without an untenable hit to the economy. Cap and trade programs like the Emissions Trading System in Europe are at least more effective at saddling the airlines with the responsibility for paying for their pollution, but in America, similar schemes have been quickly thwarted by legal challenges from the airlines. Even the Green New Deal is vague when it comes to transportation emissions. New, low-emission electrofuels—which use electricity to convert carbon dioxide into combustible fuels sources—are also on the horizon, but for now they cost between three and six times as much as kerosene. An analysis from the ETS concluded that “electrofuel uptake will increase ticket prices by 59 percent, resulting in a 28 percent reduction in projected passenger demand compared to a business-as-usual scenario.” Similar price barriers have also prevented the industry from adopting biofuels as a more ecological alternative.

The harsh reality of the situation is that nobody in aviation—including the passengers—can afford to pay for the damage they’re inflicting on the environment. But without some fantastical technological revolution, that’s it: The only solution is to make flying more expensive. “There aren’t many votes in that are there?” says Hemmings. “So do we seize on offsets that don’t do anything about aviation emissions? Or do we be brave and call for dramatic initiatives to increase the cost of aviation and reduce emissions? That’s the dilemma that Sen. Sanders and everyone else around the world has to face because there are no free lunches.” (The Sanders campaign did not respond to multiple requests for comment.)

There are also other ways to reduce the environmental impact of a presidential campaign. The easiest one is to simply travel less. “Is there a reasonable alternative to flying?” asks Borken-Kleefeld. “Is it feasible to substitute the trip by a video presence or a telepresence or a placeholder who is coming on [the candidate’s] behalf?” The problem with this approach is obvious: You can’t shake hands with a screen. And while the evidence that political campaigns can change voters’ minds at all is shaky to begin with, science has shown that intensive one-on-one conversations have true, durable power to flip opinions, suggesting that door-to-door, in-person campaigning might be one of the only tools a politician has to woo swing voters.

If the Democrats were serious about cutting carbon in any way they could, they could also optimize their travel schedule to minimize how much they had to fly, but taking the campaign bus is slow and trades time spent with voters for time spent in transit. And a schedule optimized for reducing emissions is not a schedule optimized for winning.

If a candidate has to fly, at least they might opt for the economy option: Being crammed into the plane reduces your carbon footprint by half versus flying business class, says Borken-Kleefeld. Any candidate who is serious enough about the environment to endure the reduced legroom and stale pretzels of economy might just be serious enough to take real action against aviation emission. And even if the Democratic field is flying first class, at least they’re not condoning gutting the Clean Air Act, pulling out of the Paris Agreement, or cozying up to every oil and coal lobbyist within arm’s reach—like the current White House occupant.