A new study by scientists at the Carnegie Institution suggests that while removing excess carbon dioxide would cool the planet, complexities of the carbon cycle would limit the effectiveness of a one-time effort. To keep carbon dioxide at low levels would require a long-term commitment spanning decades or even centuries.
Previous studies have shown that reducing carbon dioxide emissions to zero would not lead to appreciable cooling, because carbon dioxide already within the atmosphere would continue to trap heat. For cooling to occur, greenhouse gas concentrations would need to be reduced. "We wanted to see what the response would be if carbon dioxide were actively removed from the atmosphere," says study coauthor Ken Caldeira of Carnegie's Department of Global Ecology. "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 dioxide concentrations low. This has obvious implications for the public and for policy makers as we weigh the costs and benefits of different ways of mitigating climate change."
For the study, Caldeira and lead author Long Cao, also at Carnegie, did not focus on any specific method of capturing and storing carbon dioxide from the ambient air. The possibilities include approaches as diverse as industrial-scale chemical technologies and changing land use so more carbon dioxide is naturally absorbed by vegetation. For the study, the researchers used an Earth system model under projected conditions at the middle of this century when global surface temperatures have been raised 2° C (3.6° F). They then simulated the effects of an idealized case in which carbon emissions were reduced to zero and carbon dioxide in the atmosphere was instantaneously restored to pre-industrial levels.
The researchers found that removing all human-emitted carbon dioxide from the atmosphere caused temperatures to drop, but it offset less than half of CO2-induced warming. Why would removing all the extra carbon dioxide have such a small effect? The researchers point to two primary reasons. First, slightly more than half of the carbon dioxide emitted by fossil-fuels over the past two centuries has been absorbed in the oceans, rather than staying in the atmosphere. When carbon dioxide is removed from the atmosphere, it is partially replaced by gas coming out of ocean water. Second, the rapid drop in atmospheric carbon dioxide and the change in surface temperature alters the balance of the land carbon cycle, causing the emission of carbon dioxide from the soil to exceed its uptake by plants. As a result, carbon dioxide is released back into the atmosphere.
According to the simulations, for every 100 billion tons of carbon removed from the atmosphere, average global temperatures would drop 0.16° C (0.28° F).
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.
"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. A more prudent plan might involve preventing carbon dioxide emissions now rather than trying to clean up the atmosphere later."
The Carnegie Institution (carnegiescience.edu) has been a pioneering force in basic scientific research since 1902. It is a private, nonprofit organization with six research departments throughout the U.S. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science. The Department of Global Ecology, located in Stanford, California, was established in 2002 to help build the scientific foundations for a sustainable future. Its scientists conduct basic research on a wide range of large-scale environmental issues, including climate change, ocean acidification, biological invasions, and changes in biodiversity.
Safeguarding sustainability through forest certification mapping
27.06.2017 | International Institute for Applied Systems Analysis (IIASA)
Dune ecosystem modelling
26.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers
Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...
Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.
At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...
3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects
A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
21.07.2017 | Event News
19.07.2017 | Event News
12.07.2017 | Event News
26.07.2017 | Health and Medicine
26.07.2017 | Life Sciences
25.07.2017 | Physics and Astronomy