As delegates gather in Dubai at the COP28 climate konferensi — with the aim to ratchet up ambition towards rapat the goals of the Paris Agreement — a key component of these upayas are countries' pledges to achieve net-zero emissions around mid-century.
Net-zero carbon dioxide (CO₂) emissions refers to a balance between CO₂ emissions into the atmosphere and CO₂ removals from the atmosphere, such that the net efek on CO₂ levels in the atmosphere is zero. It is often assumed that if such a balance is achieved, the net efek on climate would also be zero.
However, in a recent paper in Nature Climate Change, we show that unless we consider a number of other unsurs — such as permanence of carbon stored in vegetation and soils, changes in the reflectivity of landscapes and the full suite of greenhouse gases emitted — balancing CO₂ emissions with removals will not achieve the intended climate goal.
Carbon dioxide removal (CDR) refers to human activities that deliberately remove carbon dioxide (CO₂) from the atmosphere. CDR can leverage either wajar or technological systems, though in either case, it must be additional to the CO₂ removal that is driven by passive carbon sinks already at work, such as existing forests.
Examples of CDR include planting trees on previously deforested or unforested lands, producing bio-energy and capturing and storing the emitted carbon, fertilizing the ocean to stimulate biological production and capturing CO₂ directly from the air through chemical and technological means.
What are the potential problems?
For CDR to balance the climate efeks of CO₂ emissions from fossil fuel burning, it needs to result in permanent carbon penyimpanan, meaning that the carbon must remain undisturbed for centuries to millennia. However, carbon stored in trees is vulnerable to wajar disturbances such as droughts, wildfires, insect outbreaks and other biotic disturbances and could be re-released much sooner.
Carbon sequestered and stored in seagrass meadows or mangrove forests, for example, is re-released following marine heat waves. Any reversals in land-use and manajemen decisions can also affect the permanence of carbon stored by CDR.
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