Britain's largest undeveloped oil field has revealed the full extent of its environmental impact if it receives government approval.
Developers of the Rosebank oil field have said that the use of petroleum products from the field will release about 250 million tons of planet-warming gas.
The amount will change each year, but for comparison, the UK's annual emissions in 2024 were 371 million tonnes.
The mine developer said its emissions were “negligible” given the UK's international climate commitments.
But opponents called it “an acknowledgment of the enormous damage from climate change” the project would cause.
Rosebank is an oil and gas field located approximately 80 miles north-west of Shetland and is one of the largest undeveloped fossil fuel deposits in UK waters.
It is said to contain up to 300 million barrels of oil and some gas and is owned by Norwegian energy giant Equinor and British firm Ithaca Energy.
The field was originally approved in 2023, but in January a court ruled that a more detailed assessment of the field's environmental impact was needed, taking into account the climate impact of burning any fossil fuels produced from it.
Public consultations are open and will last until November 20, 2025.
The Energy Minister will then decide whether to support granting consent for the project.
Greenpeace UK senior campaigner Paul Morozzo said the new figures were a “blatant admission… of the enormous climate damage that will be caused by burning Rosebank's oil and gas”.
Until recently, such projects were only required to consider the environmental impacts of fossil fuel extraction.
But in June last year the Supreme Court ruled that authorities must consider the consequences of using these products after a Surrey woman challenged the development of her local gas project.
The ruling was then used by environmental campaigners Uplift and Greenpeace in a further challenge to the Rosebank oil field, which subsequently succeeded in January.
Equinor had to recalculate the “total impact” of the field. and now he evaluates that it would contribute an additional 249 million tons of planet-warming CO2 gas over the next 25 years.
This is more than 50 times the original figure of 4.5 million tons obtained from oil and gas production.
Tessa Khan, chief executive of environmental campaign group Uplift, said Rosebank would be a test of the government's credibility on climate change.
“This huge oil field does not meet the UK's climate commitments. There is already far more oil in the world than is safe to burn,” she said.
The UK has set a target of zero additional emissions by 2050, and Energy Secretary Ed Miliband has been vocal about the need to transition away from fossil fuels.
On Tuesday, he spoke at an industry conference that the UK's dependence on fossil fuels was its “Achilles heel” and argued that clean energy was the only way to cut bills.
Fossil fuels from the Rosebank site are not guaranteed to be used in the UK, but will be sold on the international market.
Thus, the project is unlikely to have an impact on reducing gas prices. The UK's independent climate consultants said in 2022 that any further domestic oil and gas production would have “at best a minor impact on prices”.
But Arne Gurtner, Equinor's senior vice president in the UK, previously said: “If the UK needs Rosebank oil, it will flow into the UK through open market mechanisms.”
