Just four days after landmark climate talks in Scotland in which Joe Biden vowed the US will “lead by example” in tackling dangerous global heating, the president’s own administration is providing a jarring contradiction – the largest ever sale of oil and gas drilling leases in the Gulf of Mexico. The US federal government is on Wednesday launching an auction of more than 80m acres of the gulf for fossil fuel extraction, a record sell-off that will lock in years, and potentially decades, of planet-heating emissions. The enormous size of the lease sale – covering an area that is twice as large as Florida – is a blunt repudiation of Biden’s previous promise to shut down new drilling on public lands and waters. It has stunned environmentalists who argue the auction punctures the US’s shaky credibility on the climate crisis and will make it harder to avert catastrophic impacts from soaring global heating. “Coming in the aftermath of the climate summit, this is just mind boggling. It’s hard to imagine a more hypocritical and dangerous thing for the administration to do,” said Kristen Monsell, senior attorney at the Center for Biological Diversity. “It’s incredibly reckless and we think unlawful too. It’s just immensely disappointing.” Even Biden’s Democratic allies have raised concerns. “This administration went to Scotland and told the world that America’s climate leadership is back, and now it’s about to hand over 80m acres of public waters in the Gulf of Mexico to fossil fuel companies,” said Raul Grijalva, chair of the House natural resources committee. “[The] lease sale is a step in the wrong direction, and the administration needs to do better.” There is no guarantee that all the leases will be taken up by oil and gas companies but the Department of the Interior, which oversees public lands and waters, has estimated there is as much as 1.12bn barrels of oil and 4.2tn cubic ft of gas available for extraction. A separate lease sale offered by the government in Alaska’s Cook Inlet will offer up another 192m barrels of oil and 301bn cubic ft of gas to drillers. Combined, these leases would result in nearly 600m tons of planet-heating gases if fully developed over the next four decades, which is more than the total annual emissions of the UK. The sale represents a “huge climate bomb”, according to Earthjustice, one of the green groups that has lodged a lawsuit claiming it lacks a proper environmental assessment. Biden has set a target for the US to cut its emissions in half this decade before getting to net zero emissions by 2050. Critics say a worrying pattern has emerged during Biden’s tenure, with his administration handing out drilling permits at a rate of more than 300 a month since his inauguration, a faster pace even than under Donald Trump. At the Glasgow talks, known as Cop26, the US also declined to sign on to an agreement to end coal mining, or to phase out gasoline and diesel cars. “It truly calls into question whether the Biden administration’s climate agenda is nothing but broken promises,” said Jeremy Nichols of WildEarth Guardians, an environmental group. Biden struck a defiant posture against the fossil fuel industry when campaigning for the White House, stating in a Democratic primary debate last year that there will be “no more subsidies for fossil fuel industry. No more drilling on federal lands. No more drilling, including offshore. No ability for the oil industry to continue to drill, period, ends, number one.” Once in office, Biden quickly moved to realize at least part of this vision, calling a temporary halt to the issuance of oil and gas drilling permits across America’s vast publicly owned lands and ocean territory pending a review into how they are conducted. Experts have said that the development of new oil and gas fields must stop this year if the world is to avoid more disastrous heatwaves, floods and other climate impacts, with fossil fuel production on America’s public lands causing around a quarter of the country’s overall greenhouse gas pollution. However, the oil and gas industries immediately objected to Biden’s move, claiming it imperiled jobs and risked pushing up energy prices, and a dozen states sued to lift the moratorium. In June, a federal judge in Louisiana agreed with the states and found that the government hadn’t taken the required steps to pause new leases. This courtroom setback has forced the Gulf of Mexico sale, according to the Biden administration. A spokeswoman for the Department of the Interior said it is “complying” with the court ruling while also appealing it and devising a better system to measure the emissions impact of oil and gas lease sales. Jen Psaki, Biden’s press secretary, said on Monday: “It’s a legal case and legal process, but it’s important for advocates and other people out there who are following this to understand that it’s not aligned with our view, the president’s policies, or the executive order that he signed.” But legal experts say the court decision doesn’t, in itself, prevent the administration from stopping or delaying a scheduled lease sale, or from scaling it back. “The Louisiana opinion doesn’t force the administration to move forward with any particular lease sale – the Department of Interior still has discretion over that,” said Max Sarinsky, a senior attorney at the New York University School of Law. “If they were to postpone, I’m almost certain they would be sued by oil and gas interests, but that’s another matter.” To many living on the Gulf’s coast, the huge expansion in oil drilling, reaching down through up to two miles of ocean into the seabed, raises concerns over a repeat of the numerous oil spills that have caused varying degrees of devastation to coastal communities and wildlife. “That’s a fear we live with,” said Anne Rolfes, director of the Louisiana Bucket Brigade, an environmental group based in New Orleans. “There are spills every year and nothing is done to stop it – all the technology goes into how to drill further out, not to clean up spills or pipeline repair. The industry is like a cancer, it’s just relentless growth. It’s disappointing Biden won’t take a firmer stance.” This article was amended on 17 November 2021 to correct a typo and the rate at which the Biden administration is giving out drilling permits.