Californian scientists said a fossil fuel phase-out is achievable that would contain climate change, deliver energy entirely from wind, water and sunlight to 139 nations, and save up to 7 million lives each year.
They said it would also create a net gain of 24 million long-term jobs, all by 2050, and at the same time limit global warming to 1.5°C or less.
The roadmap is entirely theoretical, and depends entirely on the political determination within each country to make the switch work. But, the researchers argued, they have provided a guide towards an economic and social shift that could save economies each year around $20 trillion in health and climate costs.
The scientists have provided the calculations for only 139 of the 195 nations that vowed in Paris in 2015 to contain global warming to "well below" 2°C, because these were the nations for which reliable energy data was publicly available.
But these 139 nations account for perhaps 99 percent of all the carbon dioxide emitted by human combustion of fossil fuels. And the clean-energy answer covers all economic activity—electricity, transport, heating and cooling, industry, agriculture, forestry and fishing.
"Policymakers don't usually want to commit to doing something unless there is some reasonable science that can show it is possible, and that is what we are trying to do," said Mark Jacobson of Stanford University's atmosphere and energy program.
"There are other scenarios. We are not saying that there is only one way we can do this, but having a scenario gives people direction."
Jacobson and 26 colleagues reported in the journal Joule that their roadmaps to a new energy world free of fossil fuels and of nuclear energy can be achieved without the mining, transporting or processing of fuels.
According to their roadmaps, 139 nations could be 80 percent complete by 2030 and entirely committed to renewable sources by 2050. Jobs lost in the coal and petroleum industries would be more than compensated for by growth in the renewable sectors, and in the end, there would be more than 24 million new jobs worldwide.
Energy prices would become stable, because fuel would arrive for free: there would be less risk of disruption to energy supplies because sources would be decentralized. And energy efficiency savings that go with electrification overall could reduce "business-as-usual" demand by an estimated 42.5 percent.
"Aside from eliminating emissions and avoiding 1.5°C degrees global warming and beginning the process of letting carbon dioxide drain from the earth's atmosphere, transitioning eliminates four to seven million air pollution deaths each year and creates over 24 million long-term full-time jobs by these plans," professor Jacobson said.
"What is different between this study and other studies that have proposed solutions is that we are trying to examine not only the climate benefits of reducing carbon but also the air pollution benefits, job benefits and cost benefits."
The study is an extension of earlier research by professor Jacobson at Stanford: he has presented a master plan for renewable energy for all 50 U.S. states, and along with other researchers presented detailed arguments for the most efficient use of wind power, and even proposed that as a bonus wind turbines could sap the ferocity of hurricanes.
His is not the only group to calculate that the U.S. could free itself of fossil fuels and their associated costs. Nor is his the only group to make the case that clean power can save money and lives in the U.S. and elsewhere.
But the new study recognizes that global conversion from fossil fuels to sunlight, water and wind power won't be easy. The European Union, the U.S. and China would cope better because there is greater available space per head of population: small densely-populated states such as Singapore would face greater challenges.
There is also the challenge of political will: President Trump has announced that rather than work with the rest of the world to reduce the risks of climate change, the U.S. will withdraw from the 2015 Paris agreement, and other researchers have repeatedly pointed out that the Paris accord is itself not enough, and is not being acted upon with sufficient vigor, anywhere.
Nor will the process be without contention. Professor Jacobson has lately been the focus of a bitter academic argument about whether fossil fuels can be entirely phased out without recourse to clean coal, nuclear energy and biofuels.
But the study in Joule excludes nuclear power because of the high costs, the hazards and the problems of disposing of waste. Biofuels and coal in any form also cause pollution.
The Stanford team wants to see what could be called a clean break with the past. Space shuttles and rockets have already been powered by hydrogen, aircraft companies are exploring the possibility of electric flight; underground heat storage—to cope with fluctuating demand—would be a viable option, and shared or "district" heating already keeps 60 percent of Denmark warm.
The switch to renewables would require massive investment, but the overall cost would be one fourth of what fossil fuel dependency already costs the world.
"It appears we can achieve the enormous social benefits of a zero-emission energy system at essentially no extra cost," said Mark Delucchi of the Institute of Transportation Studies, University of California Berkeley, a co-author.
"Our findings suggest that the benefits are so great that we should accelerate the transition to wind, water, and solar, as fast as possible, by retiring fossil-fuel systems early wherever we can."