Congratulations, everybody. We did it. It’s March 24, 2021—tomorrow morning!—and we’ve woken up to discover just sitting there in the garage a boundless zero-carbon technology. What do you think it is? Nuclear fusion? Thorium-fueled reactors? Static generators powered by rubbing balloons on our hair? It doesn’t matter. Whatever it is, we’re finally safe. Innovation works.


They double-check their math, and sure enough, a monumental innovation would reduce our CO₂ load by only 7.5% by 2050, when scientists say net emissions should cease. (For scale: The UN Environment Program said (in 2019) we need 7.6% declines in all emissions every year through 2030.)

That’s because it might take a decade to bring this zero-carbon miracle to market, and the better part of another decade to design and build plants. What’s worse is this: In the time it takes the new industry to grow, coal and gas plants will continue to be built and last 30 years or more. Even with fusion tomorrow, we’d make it to 2050 without retiring much of the CO₂-spewing infrastructure that needs replacement yesterday.

Something else happens, too. Having abundant energy means that people use more of it. Energy consumption rises overall, by 6% in this scenario, cutting into the potential benefits of the new technology.

Consequently, emissions remain high.

This is one scenario suggested by a global climate-policy simulator called En-ROADS, developed by Climate Interactive, Ventana Systems, and MIT Sloan School of Management. Last year, we worked with the creators on a feature story that explains what happens in the model behind the scenes and allows readers to test their wits at saving the planet.

What’s true of the new no-carbon technology scenario is true of several other popular approaches: They take too long to stop emissions now. Trees don’t reach canopy-height overnight. By 2080, new forests could draw 6 gigatons of CO₂ out of the air, or about 16% of 2019 emissions. Not too shabby! But not enough and not soon enough. There are several other carbon-removal approaches that include capturing CO₂ directly from air, locking carbon in soils, and accelerated mineral formation. Add these to the mix, under circumstances so favorable that they’re improbable, and potential warming by 2100 comes down by half a degree Celsius—a monumental help. This En-ROADS scenario is bullish on carbon-removal tech but still doesn’t put its projections within reach of the Paris Agreement.

With a still-new administration peering into every corner of the White House for emissions to cut, and with interest-groups lining up to lobby for their favored climate fixes, it’s worth pulling out En-ROADS for a quick check on how the many elements of energy and industrial systems can work together to turn CO₂ emissions up or down. “The system is great for showing the lack of silver bullets,” said Glen Peters, research director of the Center for International Climate Research in Oslo.

Users can test how any combination of 18 policy levers (and hundreds of changeable assumptions) affect emissions, economics, and the temperature. Andrew Jones, co-director of Climate Interactive, says that often lost in political debates about competing climate solutions is how quickly they cut CO₂. Emissions need to drop as soon as possible, in the 2020s and 2030s, and many popular technology ideas that we nonetheless require don’t provide benefits until the second half of the century.