Developed over 15 years ago, the scientific foundation of net zero does not account for these natural carbon sinks in measuring net human-induced CO2 emissions. While natural sinks help mitigate existing emissions and stabilize global temperatures after net zero is reached, increasing dependence on them by governments and corporations to offset emissions rather than reducing fossil fuel use or adopting permanent CO2 storage solutions is problematic. This reliance is further incentivized by current emissions accounting standards, which equate fossil fuel emissions with CO2 absorption by natural sinks, creating a misleading impression of achieving net zero while continuing to contribute to warming.
The study urges a clearer definition of how natural carbon sinks are factored into climate targets and advocates for the concept of Geological Net Zero. This approach requires balancing carbon inflow and outflow within the Earth's crust, ensuring that any CO2 emissions from fossil fuel use are matched by equivalent CO2 committed to long-term geological storage. Achieving this will necessitate significant cuts in fossil fuel consumption due to the complexity and expense of permanent CO2 storage.
The research team underscores the importance of maintaining natural carbon sinks but asserts that they cannot offset continued fossil fuel emissions. Historical emissions determine a country or company's reliance on these natural sinks. For instance, the UK, with substantial historical emissions and limited natural sink capacity, implicitly depends on other nations to maintain these natural carbon absorbers well beyond the UK's net zero date - an aspect not adequately addressed in climate negotiations.
Professor Myles Allen, who spearheaded the study, explained, "We are already counting on forests and oceans to mop up our past emissions, most of which came from burning stuff we dug out of the ground. We can't expect them to compensate for future emissions as well. By mid-century, any carbon that still comes out of the ground will have to go back down, to permanent storage. That's Geological Net Zero."
Dr. Glen Peters from the CICERO Center for International Climate Research in Oslo and co-author of the study added, "Countries report both emissions and removals, but using all removals in climate targets is a recipe for continued warming. Natural carbon sinks currently clean up around half our annual emissions for free, but this ecosystem service must be kept separate from the fossil emissions driving climate change. Relabelling things will not stop global warming."
Professor Kirsten Zickfeld from Simon Fraser University in Canada, another co-author, stated, "It is a common assumption that removing carbon from the atmosphere to offset burning of fossil fuels is as effective as not burning fossil fuels in the first place. It is not. Offsetting continued fossil fuel use with carbon removal will not be effective if the removal is already being counted on as part of the natural carbon cycle and if the carbon is not permanently stored. Unless we can increase transparency in national Greenhouse gas reporting and target setting, offsets will become part of the problem instead of part of the solution."
Professor Jo House of the University of Bristol pointed out, "Land is limited, we rely on it for food, nature, biodiversity, leisure, water storage, and so on. It cannot offset more than a portion of fossil emissions even now, probably less in future with worsening pressures on the biosphere such as population increase, fires, and drought. Giving carbon credits for natural processes that are happening anyway undermines trust in the whole idea of offsetting. We have to urgently protect natural carbon sinks, but there are more scientifically credible and equitable ways of doing this than relying on carbon offset markets."
Geological Net Zero and better accounting for carbon sinks remain essential in crafting transparent and effective climate strategies.
Research Report:Geological Net Zero and the need for disaggregated accounting for carbon sinks
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