ExxonMobil and Shell would cease to exist in their current forms in 35 years’ time under measures UN negotiators are considering for a legally enforceable global climate pact to be sealed in Paris next year.

The oil and gas such companies produce, and the coal mined by groups such as Rio Tinto, would have to be phased out by 2050 in one proposal at UN climate talks in Lima this week that aim to smooth a path to the Paris deal.

Another option would still allow such fossil fuels to be used, but only if countries could ensure “net zero emissions by 2050”. In other words, all the warming carbon dioxide emissions produced when fossil fuels are burned would have to be stored underground or offset by steps such as planting vast numbers of trees to absorb the carbon dioxide.