The manmade emissions fueling global warming are accumulating so quickly in the atmosphere that climate change could spiral out of control before humanity can take measures drastic enough to cool the earth’s fever, many climate scientists say.
The most important way the earth’s rising temperature can be tempered is to reduce the use of fossil fuels. But scientists say another critical solution is to physically remove greenhouse gases from the atmosphere — something called “negative emissions” — so that carbon dioxide and rising temperatures could peak, and then begin to decline over time.
Many of the assumptions underlying the landmark Paris Climate Agreement rely on the idea that humans will be actively removing carbon from the atmosphere late this century because reducing emissions won’t be enough to prevent global warming from exceeding levels considered dangerous.
But that assumption relies on technology that hasn’t been proven to work on a global scale. Removing carbon dioxide from the atmosphere on a scale large enough to slow global warming is untested, and the technology is in its infancy. The effect it could have on the earth is largely unknown, and some scientists warn that some of the consequences of using negative emissions technology could be catastrophic.
Because of all those unknowns, it’s critical that humanity doesn’t bet its future on negative emissions, Stanford University Woods Institute for the Environment scientists Katharine Mach and Christopher Field write in a paper published Thursday in the journal Science.
The paper argues that both negative emissions technology and a commitment to quickly cutting carbon dioxide emissions as much as possible are critical to solving the climate crisis.
Carbon concentrations in the atmosphere must not exceed 450 parts per million (ppm) if global warming is to be prevented from exceeding a level considered dangerous by most climate scientists — 2 degrees Celsius (3.6 degrees Fahrenheit), the primary goal of the Paris Climate Agreement. The problem, though, is that humanity is quickly running out of time to limit more warming. The atmosphere blew past the 400 ppm mark last September and it’s on a trajectory to pass 450 ppm within 22 years.
Most of the Intergovernmental Panel on Climate Change models underlying the Paris Climate Agreement assume some level of large-scale carbon removal will be occurring in the coming decades, but nobody knows exactly how that will be accomplished.
Ben Sanderson, a climate scientist at the National Center for Atmospheric Research who is unaffiliated with the paper, said the study shows that carbon removal shouldn’t be treated as a cure-all for climate change because the future of humanity can’t rely on untested technology.
“The major risk is that the planned-for CO2 removal might never come to pass — and this is a very real concern,” Sanderson said.