A new study by scientists at the Carnegie Institution for Science suggests that while removing carbon dioxide emissions would cool the planet, the complexities of the carbon cycle would limit its effectiveness. Reducing carbon dioxide emissions even to zero will not lead to appreciable cooling because carbon dioxide already in the atmosphere will continue to trap heat.
The Carnegie scientists arrived at these conclusions through the help of an earth model simulating the effects of an idealized case where carbon emissions have been reduced to zero and carbon dioxide in the atmosphere was restored to pre-industrial levels.
Ken Caldeira of Carnegie’s global ecology department and lead author Long Cao found that removing all human-emitted carbon dioxide from the atmosphere did cause some climate cooling but it negated less than half of the already induced warming.
It is basically a case of action coming too late and at a time when the situation has become complicated, as two main factors show.
Slightly more than half of the carbon dioxide emitted by industries over the past two centuries has been absorbed by the oceans. The study showed that carbon dioxide removed from the atmosphere was partially replaced by gas coming out of the blue waters.
The rapid drop in atmospheric carbon dioxide and the change in surface temperature have also altered the land carbon cycle. In turn, the altered balance of the land carbon cycle caused the emission of carbon dioxide from the soil to exceed its uptake by plants.
Overall, the ocean and land emitted carbon dioxide that replaced the ones removed from the atmosphere.
Carbon emissions have been a part of our planet since its beginning. Absorption into the ocean and via land has always been the natural way of keeping their levels down. But with the rise in emissions via industrial or man-based activities, it seems we have taxed the natural cycles a bit too much.
According to the simulation, for every 100 billion tons of carbon removed from the atmosphere, average global temperatures would only drop by 0.16°Celsius or 0.28°Fahrenheit.
Futile effort?
The study does not intend to show that realizing a low-carbon economy is a futile move in responding to climate change. Instead, it suggests that if there is ever a time for acting, that is now.
“If we do someday decide that we need to remove carbon dioxide from the atmosphere to avoid a climate crisis, we might find ourselves committed to carbon dioxide removal for a long, long time,” says Mr. Caldeira.
Further simulations showed that in order to keep carbon dioxide at low levels, the process of extracting carbon dioxide from the air would have to continue for many decades and perhaps centuries after emissions were halted.
“A more prudent plan might involve preventing carbon dioxide emissions now rather than trying to clean up the atmosphere later,” Mr. Caldeira added.
Possible approaches to capturing and storing carbon dioxide from ambient air include processes as diverse as industrial-scale chemical technologies and changing land use.
“Our study is the first to look at how much carbon dioxide you would need to remove and for how long to keep atmospheric carbon concentrations low,” said Mr. Caldeira.
Until the planet’s carbon balance is restored, we will have to help nature “clean up” after us and ensure that we do not tip the balance irrevocably.
