2017-2020: All countries would prepare for the herculean task ahead by laying vital policy groundwork. Like: scrapping the $500 billion per year in global fossil fuel subsidies. Zeroing out investments in any new coal plants, even in countries like India and Indonesia. All major nations commit to going carbon-neutral by 2050 and put in place policies — like carbon pricing or clean electricity standards — that point down that path. ”By 2020," the paper adds, ”all cities and major corporations in the industrialized world should have decarbonization strategies in place."
2020-2030: Now the hard stuff begins! In this decade, carbon pricing would expand to cover most aspects of the global economy, averaging around $50 per ton (far higher than seen almost anywhere today) and rising. Aggressive energy efficiency programs ramp up. Coal power is phased out in rich countries by the end of the decade and is declining sharply elsewhere. Leading cities like Copenhagen are going totally fossil fuel free. Wealthy countries no longer sell new combustion engine cars by 2030, and transportation gets widely electrified, with many short-haul flights replaced by rail.
In addition, spending on clean energy research increases by ”an order of magnitude" this decade, with a sustained focus on developing new batteries, drastically reducing the cost of carbon capture and storage (CCS), and perfecting low-carbon processes for producing steel and concrete, plus improving smart grids, greener aircraft systems, and sustainable urbanization techniques.
Meanwhile, efforts to start pulling carbon dioxide out of the air start this decade. That means reforesting degraded land and deploying technologies such as direct-air capture or bioenergy with CCS to pull CO2 out of the atmosphere. By 2030, we'd need to be removing 100 to 500 megatons of CO2 each year and have a sense of how to scale up.
2030-2040: By this decade, hopefully, we're reaping the fruits of major technological advances in clean energy. Leading countries like Denmark and Sweden should now have completely carbon-free grids and have electrified virtually all of their transport, heating, and industry. Cars with internal combustion engines ”will have become rare on roads worldwide." (Let that sink in.) Aircraft will be almost entirely powered by carbon-neutral fuels, say, biofuels or hydrogen. New building construction will be largely carbon-neutral, by using emissions-free methods for steel and concrete or through other techniques. And ”radical new energy generation solutions will enter the market."
Meanwhile, we'd need to be sucking about 1 to 2 gigatons of CO2 from the air each year, with a heavy R&D effort on expanding that further.
2040-2050: By the early 2040s, major European countries are close to carbon-neutral, and the rest of the world is moving toward that goal by the end of the decade. Electricity grids are nearly entirely carbon-free: ”Natural gas still provides some back up energy, but CCS ensures its carbon footprint is limited. Modular nuclear reactors may contribute to the energy mix in some places." Lower-income countries are still using some fossil fuels, and the world is still emitting a small bit of CO2 in 2050 (about one-eighth the amount of today), but work continues on eventually phasing that out.
Finally, by 2050, we'd need to be removing more than 5 gigatons of CO2 per year from the atmosphere. It's possible this is simply impractical — if we tried to do that all by burning biomass for energy and sequestering the resulting carbon (a ”negative emissions" process), we might well run into serious land constraints that hinder agriculture. If, in the 2020s, we realize this will be the case, then we'll have to revamp the road map to cut CO2 emissions from energy and industry even faster.
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