Since Russia closed its airspace to airlines from dozens of countries at the end of February – in response to sanctions levied for its invasion of Ukraine – about 400 flights per month that had previously been routed over the country are being forced to take a wider berth, according to Flightradar24. In lieu of using Russian airspace, some flights from Europe to Asia are flying south of the country or, in some cases, taking a painfully long reroute over the Arctic. And Russia is huge; it’s the largest country on the planet – larger than the continent of Antarctica. The new routes are leading to more time in the air for passengers and crew, more miles flown and more fuel burned – which means more planet-warming emissions. Japan Airlines Flight JL43 from Tokyo to London, for instance, uses a Boeing 777-300ER aircraft that burns roughly 2,300 gallons of fuel per hour. The rerouted JL43 flight – which now heads east over the North Pacific, Alaska, Canada and Greenland – added 2.4 hours of flight time and likely burned around 5,600 gallons more fuel, a 20% increase. That means Flight JL43 could be emitting an additional 54,000 kilograms, or 60 tons, of planet-warming carbon dioxide into the atmosphere, according to calculations by Paul Williams, an atmospheric scientist at the University of Reading, for CNN. That’s the same amount of carbon dioxide as the average car driving 137,000 miles, or nearly six times around the planet. Williams said the exact fuel burn rate depends on the weight of the aircraft, the altitude and airspeed, and some of those variables are unknown. These calculations also do not factor in the warming effect of other greenhouse gas emissions or the flights’ condensation trails. “Naturally, a lot of people when thinking about aviation and climate, they focus on the CO2 emitted,” Williams told CNN. “But, actually, it’s much worse than that. CO2 is actually just the tip of the iceberg. The extra flight time is causing a lot more warming than the mileages I gave you because they only take into account the CO2, not the other non-CO2 effects.” Dan Rutherford, director of the International Council on Clean Transportation’s aviation and marine programs, told CNN that Williams’ calculations “look reasonable.” “If anything, he is underestimating the likely impact because, at the margin, long-haul flights become even more fuel intensive with extra distance because they ‘burn fuel to carry fuel,’ in industry parlance,” Rutherford said. In other words, it’s a vicious, fuel-guzzling loop: It takes more fuel to carry the weight of more fuel. According to Flightradar24, the aircraft tracking service, there are a limited number of flights – mostly Finnair flights – taking the polar route around Russia. Others are taking a southern route. Lufthansa Flight LH716 from Frankfurt to Tokyo, for example, has added nearly an hour to its flight time. The Airbus A340 aircraft typically burns around 2,000 gallons of fuel an hour, which could mean the extra flight time burned another 1,428 gallons of fuel. That’s an additional 13,710 kilograms of planet-warming emissions – the same amount released by an average car driving 34,000 miles, or nearly twice around the world. Rutherford estimated that if Russian airspace remains closed for much longer, the global aviation carbon inventory may increase by up to 1%. That seems very low, but air travel is a significant contributor to the climate crisis, accounting for more than 2% of the world’s carbon dioxide emissions as of 2018, according to the Environmental and Energy Study Institute. The institute notes that if the aviation industry were its own country, it would rank No. 6 in carbon emissions. “[However], I consider that a marginal impact that governments shouldn’t consider when setting policy regarding the Ukrainian invasion,” Rutherford told CNN. “It’s a small price to pay to defend global democracy and the international rule of law, in my personal opinion.” Flying can make up a huge portion of a person’s carbon footprint. For instance, a one-way intercontinental flight between Hong Kong and San Francisco emits more carbon dioxide than the average British person’s activities – or that of 10 people living in Ghana – over the course of a year, according to a 2020 analysis published in the journal Nature. “Fly less” is often the first line of expert advice for people looking to reduce their climate impact. But with the aviation industry struggling to decarbonize, Williams said he expects emissions from aviation to only increase over time. “Aviation is finding it really difficult to decarbonize than the rest of the economy,” he said. “Because the plane needs so much energy to generate the thrust, it’s really problematic to move away from fossil fuels. So aviation is a small part of the jigsaw currently, but in the coming decades, it will grow as a fraction of global emissions.” But right now, the extra emissions are unavoidable, Williams said. There are no other options than taking the long way around Russia. Airlines can invest in new, more efficient aircrafts and shift to sustainable aviation fuels, Rutherford said, but those are long-term solutions. Short-term strategies are limited. “The extra fuel use and emissions, and also extra fuel cost due to higher oil prices generally, are basically inescapable for airlines,” Rutherford said. “In addition to paying more, they can reduce payload – passengers or carriage – at the cost of some revenue, or they can cancel the flight.” In February, UN Secretary-General António Guterres said that the “current events” showed the world was too reliant on fossil fuels, calling them “a dead end.” A recent UN climate report shows that unless Earth’s warming is dramatically slowed, billions of people and other species may no longer be able to adapt to irreversible changes brought by fossil fuel emissions. Rutherford said he expects “renewed interest in developing alternative fuels in shipping and aviation, to distance those industries from Russian energy exports.” “This particular war is causing a wide rethink about getting off of fossil fuels,” he said.