The emissions from the Rosebank and Jackdaw fields could cause enough heat deaths to wipe out the population of Inverness, a new analysis has found.
The proposed developments were ruled unlawful by the Court of Session following a legal challenge, with revised plans to go before the UK Government.
The Labour Party manifesto pledged not to issue any new licenses to explore new oil and gas fields.
This summer has seen heat waves across Europe, with water levels in the Danube so low that Hungary was forced to almost completely shut down the Paks nuclear power plant and old Second World War ships and ordnance were uncovered by the receding water.
Wildfires have blazed in France, all major Italian cities were on red heat alert on Friday and in Děčín in the Czech Republic the level of the Elbe fell so low it uncovered a 'hunger stone' traditionally seen as a harbinger of famine because it only appears when water is incredibly scarce.
Campaigners warn that approving the controversial North Sea projects would lock in decades of additional emissions at a time when communities are already experiencing the impacts of a heating planet, from raging wildfires and record-breaking temperatures to drought across large parts of the UK.
A new analysis from Oxfam found that Rosebank alone could be linked to approximately 57,400 excess heat deaths globally over its lifetime – more than the number of babies born in Scotland in a year.
The figures use the mortality cost of carbon (MCC), a metric developed by economist R. Daniel Bressler, that estimates the number of excess deaths caused globally by future warming attributable to a given quantity of CO2-equivalent emissions, based on projected temperature-mortality relationships this century.
It has been calculated that Rosebank's lifetime emissions would equate to 57,404 heat deaths, while Jackdaw's would be 8,091, with the combined total more than the population of Inverness at 63,000.
The charity says the findings underline the consequences of making short term decisions now that will hit those living in poverty the hardest and will be felt for generations to come.
Rosebank alone is estimated to produce 254 million tonnes of carbon dioxide equivalent over its lifetime. Around 90% of its reserves are oil, with the majority expected to be sold into international markets where prices are set globally.
Campaigners say this means Rosebank would do nothing to lower household energy bills, and would provide little benefit for UK energy security, while locking the UK into further fossil fuel dependence.
Oxfam says the move away from oil and gas must be managed fairly, with North Sea workers and communities at the heart of the transition. Campaigners warn that the decline of the North Sea industry is already underway, and that the best way to protect workers and communities is not to delay that change, but to invest now in the industries of the future and support people to move into good, green, secure jobs.
Katherine May, Head of Oxfam Scotland, said: “We’re seeing raging wildfires, record-breaking temperatures and devastating droughts around the world. Against that backdrop, approving Jackdaw and Rosebank could be deadly and the consequences could reverberate for generations to come.
“More drilling is being presented as a cure for high energy bills, but it’s the wrong medicine. It would leave us even more dependent on the volatile global fossil fuel markets that have already pushed up costs. The real answer is investment in affordable renewable energy and a fair transition that supports workers and communities.