\u0394C<\/i>loss<\/sub><\/span> can be compared to the combined emissions and removals from the agriculture, LULUCF and waste (Agr+LULUCF+Waste) categories. These quantities are not identical, with the most important difference being that NGHGIs are only for managed land, while \u0394C<\/i>loss<\/sub><\/span> includes both managed and unmanaged lands. Therefore, caution is needed for parties with large unmanaged land areas (e.g., Canada or the Russian Federation). Another difference from NGHGIs is that \u0394C<\/i>loss<\/sub><\/span> implicitly includes deposition of<\/span> carbon in water body sediments within a country (such as lakes). However, this is expected to be a small contribution. Similarly, volcanic CO2<\/sub><\/span> emissions are implicitly included in \u0394C<\/i>loss<\/sub><\/span> but are also believed to be small contributions (global subaerial volcanic CO2<\/sub><\/span> emissions are \u223c0.05<\/span>\u2009Pg\u2009CO2<\/sub>\u2009yr\u22121<\/sup><\/span>,\u00a0Fischer et\u00a0al.<\/a>,\u00a02019<\/a>)<\/span>. It is worth noting that NGHGIs require estimates of turnover times for wood products in producing countries, as these can have lifetimes of decades to centuries (see Appendix\u00a03a.1 of\u00a0Penman et\u00a0al.<\/a>,\u00a02003<\/a>)<\/span>. No such estimate is needed for the top-down methods, as emissions from decaying wood products will be implicitly incorporated in NCE. Therefore, top-down methods only need to account for the lateral movement of wood products from the region where the carbon is sequestered to the region where the wood products are used and decompose.<\/p>\n For this analysis, we compare NGHGIs and our dataset for three entities: the USA, European Union plus the United Kingdom (EU27+UK) and Australia. These were chosen for two reasons. First, NCE is better constrained by atmospheric CO2<\/sub><\/span> data over these relatively large regions. This is reflected in the FUR metric, which gives values of 0.76\u20130.91 for the USA (meaning a 76\u2009%\u201391\u2009% uncertainty reduction), 0.38\u20130.51 for EU27 and 0.45\u20130.78 for Australia. Second, each of these entities has small unmanaged land areas, making this more of an apples-to-apples comparison. An area of 95\u2009% of the USA is managed, with most unmanaged land being in the state of Alaska (Ogle et\u00a0al.<\/a>,\u00a02018<\/a>)<\/span>. Similarly, all land in the EU27+UK is considered managed except for 5\u2009% of France’s territory (Petrescu et\u00a0al.<\/a>,\u00a02021<\/a>)<\/span>.<\/p>\n Figure\u00a015<\/a> shows time series of emissions and removals from NGHGIs and Byrne et\u00a0al.<\/a> (2022<\/a>)<\/span> over 2015\u20132020. We focus our analysis on the 2015\u20132020 mean estimates, as top-down methods are expected to be more sensitive to IAV in the carbon cycle than NGHGI methods for individual years. Strong agreement is found between the NGHGI Energy+IPPU emissions and the fossil fuel emissions in Byrne et\u00a0al.<\/a> (2022<\/a>)<\/span>, while larger differences are found between Agr+LULUCF+Waste and \u0394C<\/i>loss<\/sub><\/span>. Averaged over the 2015\u20132020 period, we obtain statistically significant differences between Agr+LULUCF+Waste and \u0394C<\/i>loss<\/sub><\/span> for the USA and EU27+UK for each experiment (based on Student’s t<\/i>\u00a0test at 0.05 significance level). In each case the top-down estimates suggest greater carbon sequestration by land, with mean differences of 0.59\u20130.91\u2009Pg\u2009CO2<\/sub>\u2009yr\u22121<\/sup><\/span> for the USA and 0.99\u20131.79\u2009Pg\u2009CO2<\/sub>\u2009yr\u22121<\/sup><\/span> for the EU27+UK. The reasons for these differences are unclear but are not expected to be explained by removals in unmanaged lands. It is possible that NGHGI methods miss or underestimate sink processes and\/or that there are biases affecting the top-down estimates (see Sect.\u00a09<\/a> for remaining challenges in top-down estimates). We encourage further research and comparison between the NGHGI and top-down research communities to better understand the sources of these differences.<\/p>\n![\"\"](\"https:\/\/www.fie.undef.edu.ar\/ceptm\/wp-content\/uploads\/2023\/03\/essd-15-963-2023-f15.png\")