We’ll all be heavily dependent on oil for the next 100 years, according to the world’s largest oil company, Exxon Mobil. The company, which has lagged behind its peers in pursuing renewable energy solutions, announced its belief that the transition from oil to clean energy is at least a century away because ‘there are no viable alternatives’.

Chief Executive Officer Rex Tillerson spoke to reporters after Exxon Mobil’s annual shareholder meeting in Dallas last week, asserting that petroleum-based fuels will remain the dominant sources of energy for factories, offices, homes and cars.

A plan to regulate greenhouse gas emissions introduced by Democrats in May would allocate a limited number of emissions credits to refiners and electricity producers, which would drive up the price of fuel for U.S. consumers, Tillerson complained.

“The oil-gas-refining side of the business received a very, very small amount of the allocations, which means that sector will bear more of the costs more immediately. If we’re going to place a price on carbon, let’s do that in the most efficient way. A carbon tax is more efficient than a tax that’s applied by way of a cap-and-trade mechanism.”

Tillerson also expressed doubts about the need to restrict greenhouse gases, saying that many scientific questions remain unresolved.

“We’re going to be very forthright in not accepting something that is not completely scientifically proven,” Tillerson said. “We’re not skeptics. We’re just approaching this the way we would approach any scientific challenge, and it’s a serious challenge.”

Exxon Mobil spent years funding global warming denial groups before finally cutting ties with them in 2007.