Hydrogen fuel-cell vehicles could make up 20% of the world’s vehicle fleet in 2050, if an ambitious scenario put forth by the Hydrogen Council comes to fruition.

Consultant McKinsey & Co. says the proposal to factor in hydrogen fuel as a key to meeting Paris Agreement carbon-dioxide targets is a feasible strategy, but efforts will need to be stepped up if the those clean-air objectives are to be achieved.

“Battery-electric vehicles are making headlines, but fuel cells are gaining momentum – with good reason,” McKinsey concludes in a white paper on the Hydrogen Council’s proposal. “Hydrogen could play a vital role in the renewable-energy system and in future mobility.”

McKinsey says FCVs could power some 400 million cars, 15 million-20 million trucks and about 5 million buses by 2050, if policymakers promote hydrogen use. The Hydrogen Council, a consortium of 18 automotive, equipment and energy companies, estimates a comprehensive hydrogen strategy could contribute about one-fifth of the total carbon-dioxide abatement needed to reach the 2050 Paris Agreement targets.

FCVs won’t replace battery-electrics in the future but could serve as a complementary technology, McKinsey says, with FCVs focused more on vehicles designed for longer-haul driving and BEVs targeted for use in shorter commutes.

“How the technologies relate will depend mostly on how battery technology will evolve and how quickly cost reductions from scaling fuel-cell production can be realized,” McKinsey says.

The consultancy says 80 million zero-emission vehicles will be needed on the road by 2030 to meet Paris standards, and by 2050 CO2 emissions will need to decline by 70% per passenger kilometer.

To reach the 2050 target, the market will be required to reach certain milestones along the way, the Hydrogen Council says. That includes the sale of one hydrogen-powered vehicle for every 12 cars sold in California, Germany, Japan and South Korea.

Toyota, Honda and Hyundai already are retailing FCVs in small numbers in certain markets, and McKinsey points out 10 additional models are slated for release by 2020. It expects early demand to come mostly from ride-hailing services and says ambitious national targets calling for 1.8 million FCVs on Chinese and Japanese roads by 2030 could further expand the market.

Commercial fleets also would be key targets. South Korea plans to convert 26,000 buses to hydrogen and Shanghai alone has committed to purchasing 3,000 fuel-cell buses by 2020, McKinsey says.

Globally, countries have pledged to have 2,800 hydrogen refueling stations in place by 2025, which McKinsey says would be enough to cover the leading markets for hydrogen vehicles.

The Hydrogen Council estimates investments of $280 billion will be necessary through 2030 to put hydrogen into the vehicle powertrain mix, with about 60% of that amount dedicated to producing, storing and distributing the fuel. Another 30% of that total would go to developing products and capitalizing the capacity to build them, with the remaining 10% needed for establishing 15,000 refueling stations deemed critical to long-term FCV market growth.

The Paris Agreement, signed by 195 countries, calls for global warming to be kept below 2º C above pre-industrial levels. To reach that target, the world needs to reduce energy-related CO2 emissions 60% by 2050, McKinsey says. The U.S. is not a member of the pact.