Addressing uncertainty and bias in land use, land use change, and forestry greenhouse gas inventories

National greenhouse gas inventories (NGHGIs) will play an increasingly important role in tracking country progress against United Nations (UN) Paris Agreement commitments. Yet uncertainty in land use, land use change, and forestry (LULUCF) NGHGHI estimates may undermine international confidence in emission reduction claims, particularly for countries that expect forests and agriculture to contribute large near-term GHG reductions. In this paper, we propose an analytical framework for implementing the uncertainty provisions of the UN Paris Agreement Enhanced Transparency Framework, with a view to identifying the largest sources of LULUCF NGHGI uncertainty and prioritizing methodological improvements. Using the USA as a case study, we identify and attribute uncertainty across all US NGHGI LULUCF “uncertainty elements” (inputs, parameters, models, and instances of plot-based sampling) and provide GHG flux estimates for omitted inventory categories. The largest sources of uncertainty are distributed across LULUCF inventory categories, underlining the importance of sector-wide analysis: forestry (tree biomass sampling error; tree volume and specific gravity allometric parameters; soil carbon model), cropland and grassland (DayCent model structure and inputs), and settlement (urban tree gross to net carbon sequestration ratio) elements contribute over 90% of uncertainty. Net emissions of 123 MMT CO2e could be omitted from the US NGHGI, including Alaskan grassland and wetland soil carbon stock change (90.4 MMT CO2), urban mineral soil carbon stock change (34.7 MMT CO2), and federal cropland and grassland N2O (21.8 MMT CO2e). We explain how these findings and other ongoing research can support improved LULUCF monitoring and transparency.

Deriving CO2 emissions of localized sources from OCO-3 XCO2 and TROPOMI NO2 satellite data

<p>Carbon dioxide (CO<sub>2</sub>) is the most important anthropogenic greenhouse gas and the main driver of global warming. Its atmospheric concentrations have risen more than 40% since pre-industrial times. Almost 90% of this increase results from fossil fuel combustion, emitting CO<sub>2</sub> predominantly from localized sources. In order to track the reduction efforts to comply with the objectives of the Paris Agreement, emissions need to be monitored. For this purpose, bottom-up emission estimates are regularly reported in the national greenhouse gas inventories. Top-down observation-based estimates can complement and verify these inventories. Satellite observations have an important role in this context, since they can provide global information.</p> <p>Due to CO<sub>2</sub>'s long lifetime and large fluxes of natural origin, the column-average concentrations resulting from anthropogenic emissions from individual source points are usually small compared to the background concentration, and these enhancements are often barely larger than the satellite's instrument noise. This makes the detection of CO<sub>2</sub> emission plumes and the quantification of anthropogenic fluxes challenging.</p> <p>NO<sub>2</sub> is co-emitted with CO<sub>2</sub> in the combustion of fossil fuels. It has a much shorter lifetime, and as a result, its vertical column densities can exceed background values and sensor noise by orders of magnitude in emission plumes. This makes it a suitable tracer for recently emitted CO<sub>2</sub>.</p> <p>The objective of this study is to quantify the CO<sub>2</sub> emissions from localized sources such as power plants by using XCO<sub>2</sub> (the column-averaged dry air mole fraction of CO<sub>2</sub>) retrievals from the Orbiting Carbon Observatory 3 (OCO-3) in its snapshot area mode. Our presentation describes a plume detection method using NO<sub>2</sub> as a tracer for recently emitted CO<sub>2</sub> and an inversion technique to quantify CO<sub>2</sub> emissions from detected CO<sub>2</sub> plumes.</p>

The default methods in the 2019 Refinement drastically reduce estimates of global carbon sinks of harvested wood products

Background The stock dynamics of harvested wood products (HWPs) are a relevant component of anthropogenic carbon cycles. Generally, HWP stock increases are treated as carbon removals from the atmosphere, while stock decreases are considered emissions. Among the different approaches suggested by the Intergovernmental Panel on Climate Change (IPCC) for accounting HWPs in national greenhouse gas inventories, the production approach has been established as the common approach under the Kyoto Protocol and Paris Agreement. However, the 24th session of the Conference of the Parties to the United Nations Framework Convention on Climate Change decided that alternative approaches can also be used. The IPCC has published guidelines for estimating HWP carbon stocks and default parameters for the various approaches in the 2006 Guidelines, 2013 Guidance, and 2019 Refinement. Although there are significant differences among the default methods in the three IPCC guidelines, no studies have systematically quantified or compared the results from the different guidelines on a global scale. This study quantifies the HWP stock dynamics and corresponding carbon removals/emissions under each approach based on the default methods presented in each guideline for 235 individual countries/regions. Results We identified relatively good consistency in carbon stocks/removals between the stock-change and the atmospheric flow approaches at a global level. Under both approaches, the methodological and parameter updates in the 2019 Refinement (e.g., considered HWPs, starting year for carbon stocks, and conversion factors) resulted in one-third reduction in carbon removals compared to the 2006 Guidelines. The production approach leads to a systematic underestimation of global carbon stocks and removals because it confines accounting to products derived from domestic harvests and uses the share of domestic feedstock for accounting. The 2013 Guidance and the 2019 Refinement reduce the estimated global carbon removals under the production approach by 15% and 45% (2018), respectively, compared to the 2006 Guidelines. Conclusions Gradual refinements in the IPCC default methods have a considerably higher impact on global estimates of HWP carbon stocks and removals than the differences in accounting approaches. The methodological improvements in the 2019 Refinement halve the global HWP carbon removals estimated in the former version, the 2006 Guidelines.

The analysis of carbon footprint of the settlement activity in the village of Pedurungan District, Semarang City, Central Java Province

Some important sectors influenced the increase of greenhouse gases, such as waste, transportation, settlement, and agricultural sectors. This research aimed to analyze the amount of CO2 emissions, map the carbon footprint, and analyze tree capability in reducing CO2 in 12 villages in Pedurungan district, Semarang city, Central Java. The method used was based on IPCC Guidelines for National Greenhouse Gas Inventories 2006 and Ministry of Environment 2012 about the Implementation of National Greenhouse Gas Inventories Guidelines. The carbon footprint was mapped using ArcGIS software. The results showed that the energy sector produced 13.723,35 tons CO2 Eq, the transportation sector emitted 1.624,58 tons CO2 Eq, and the waste sector emitted 7.677,08 CO2 Eq. The carbon footprint map was presented in three classifications of carbon footprint: lower, middle, and upper, represented by green, yellow, and red colors. An effort to reduce the carbon footprint was planting 300 trees of ten species in the Pedurungan district.

State forest register as basis of greenhouse gas inventory for land use, land use change and forestry sector

The data on the assessment of the dynamics of forested lands of the Republic of Belarus are presented. The characteristics of the forest fund for the period 1994–2019 are presented. Based on the materials of the provisions of international treaties, documents adopted within the framework of the implementation of the UN Framework Convention on Climate Change at the international and national levels, including the Paris Agreement, the provisions of regulatory legal acts of the Republic of Belarus, the results of scientific research, information from the Ministry of Forestry, according to the data of the State Forest Cadastre, an assessment of greenhouse gases in the forest fund of the Republic of Belarus was carried out. CO2 emissions and sinks from forestry have been calculated in accordance with the IPCC Guidelines for National Greenhouse Gas Inventories using the stock-difference method. It was found that as a result of purposeful work on reforestation and reforestation over a 26-year period, a positive dynamics of the forest fund was achieved in the Republic of Belarus: the forested area increased by 919,6 thousand ha from 7360,7 thousand ha to 8280,3 thousand ha; the forest cover of the territory of the republic increased by 4,3 % and reached 39,9 %; the total standing timber stock increased by 739,5 million m3 from 1092,3 to 1831,8 million m3 (including in mature and over-mature stands — by 300,3 million m3 and amounted to 348,8 million m3); the reserve per hectare of forested land increased by 72,8 m3 and amounted to 221,2 m3/ha; the stock of mature and over-mature stands increased by an average of 52,6 m3 and reached 273,9 m3/ha.

Evidence of a recent decline in UK emissions of hydrofluorocarbons determined by the InTEM inverse model and atmospheric measurements

National greenhouse gas inventories (GHGIs) are submitted annually to the United Nations Framework Convention on Climate Change (UNFCCC). They are estimated in compliance with Intergovernmental Panel on Climate Change (IPCC) methodological guidance using activity data, emission factors and facility-level measurements. For some sources, the outputs from these calculations are very uncertain. Inverse modelling techniques that use high-quality, long-term measurements of atmospheric gases have been developed to provide independent verification of national GHGIs. This is considered good practice by the IPCC as it helps national inventory compilers to verify reported emissions and to reduce emission uncertainty. Emission estimates from the InTEM (Inversion Technique for Emission Modelling) model are presented for the UK for the hydrofluorocarbons (HFCs) reported to the UNFCCC (HFC-125, HFC-134a, HFC-143a, HFC-152a, HFC-23, HFC-32, HFC-227ea, HFC-245fa, HFC-43-10mee and HFC-365mfc). These HFCs have high global warming potentials (GWPs), and the global background mole fractions of all but two are increasing, thus highlighting their relevance to the climate and a need for increasing the accuracy of emission estimation for regulatory purposes. This study presents evidence that the long-term annual increase in growth of HFC-134a has stopped and is now decreasing. For HFC-32 there is an early indication, its rapid global growth period has ended, and there is evidence that the annual increase in global growth for HFC-125 has slowed from 2018. The inverse modelling results indicate that the UK implementation of European Union regulation of HFC emissions has been successful in initiating a decline in UK emissions from 2018. Comparison of the total InTEM UK HFC emissions in 2020 with the average from 2009–2012 shows a drop of 35 %, indicating progress toward the target of a 79 % decrease in sales by 2030. The total InTEM HFC emission estimates (2008–2018) are on average 73 (62–83) % of, or 4.3 (2.7–5.9) Tg CO2-eq yr−1 lower than, the total HFC emission estimates from the UK GHGI. There are also significant discrepancies between the two estimates for the individual HFCs.