The 369-page report, written by a panel of the National Academies of Sciences, Engineering and Medicine, underscores an important shift. For decades, experts said that nations could prevent large temperature increases mainly by reducing reliance on fossil fuels and moving to cleaner sources like solar, wind and nuclear power.
But at this point, nations have delayed so long in cutting their carbon-dioxide emissions that even a breakneck shift toward clean energy now would most likely not be enough. According to a landmark scientific report issued by the United Nations this month, taking out a big chunk of carbon dioxide already loaded into the atmosphere may be necessary to avoid significant further warming, even though researchers haven’t yet figured out how to do so economically, or at sufficient scale.
And we’ll have to do it fast. To meet the climate goals laid out under the Paris Agreement, humanity may’ve to start removing around 10 billion tons of carbon dioxide from the air each year by midcentury, in addition to reducing industrial emissions, said Stephen Pacala, a Princeton climate scientist who led the panel.
“Midcentury is not very far away,” Pacala said. “To develop the technologies and scale up to 10 billion tons a year is something that would require a lot of activity. So the time would have to be now.” Right now, there are plenty of ideas for carbon removal kicking around. But, the National Academies panel warned, many of these methods are still unproven or face serious limitations.
It might be possible to collect wood or other plant matter that has absorbed carbon dioxide from the air, burn it in biomass power plants for energy and then capture the carbon released from combustion and bury it underground. While no such facilities are operating today, the technology to build them exists.
But one potential problem with this approach, the National Academies panel said, is the land required to grow biomass for these power plants could run into conflicts with the need for farmland. The panel estimated this method might one day be able to remove 3 billion to 5 billion tons of carbon dioxide from the air each year.