Researchers are urging for more detailed national climate goals, with distinct targets for land-based mitigation, separate from actions in other sectors ahead of the COP28 summit.
A new study highlights how climate mitigation benchmarks change, with net zero timings arriving up to five years earlier.
The study by the Integrated Assessment and Climate Change (IACC) Research Group also highlights how mitigation can lead to cumulative emissions, to net zero being 15-18% smaller.
The study states that countries have recognised the importance of the land use, land-use change, and forestry (LULUCF) sector, with 118 of 143 countries including land-based emissions reductions and removals in their Nationally Determined Contributions (NDCs).
Study co-author and researcher, Giacomo Grassi explained that LULUCF direct fluxes are a result of direct human intervention, such as agriculture and forest harvest.
He added that indirect fluxes are the response of land to indirect human-induced environmental changes, such as increases in atmospheric carbon or nitrogen deposition.
Land-based mitigation
Grassi said it is “practically not possible” to separate direct and indirect fluxes through observations such as national forest inventories or remote sensing.
The researchers found that in pathways achieving the 1.5°C long-term temperature goal of the Paris Agreement, net zero carbon emissions is achieved one-to-five years earlier.
They also found that due to this, emission reductions by 2030 need to be 3.5-6% stronger, and cumulative carbon emissions are between 55-95Gt of carbon less.
Study co-author and senior researcher, Thomas Gasser said:
“The IPCC assessment reports use direct, land-based emissions as input, and include the indirect emissions due to climate and environmental responses in their physical climate emulation to calculate the global temperature response to anthropogenic emissions.
“In our analysis, we make it clear that we’re looking at these two kinds of emissions separately.
“The climate outcome of each scenario we assess remains the same, but the benchmark – when viewed through the lens of national greenhouse gas (GHG) inventory accounting conventions – shifts. Without making adjustments, countries could appear in a better position than they actually are.”
Due to the findings of the study, the researchers are advising countries to bring “clarity” to COP28 by communicating their planned use of the LULUCF sector separately from emissions reductions elsewhere.
Study author and senior researcher, Matthew Gidden said:
“Our findings show the danger of comparing apples to oranges – to achieve the Paris Agreement, it’s critical that countries aim for the correct target.
“If countries achieve model-based benchmarks using inventory-based accounting, they will miss the mark.”
