Editing IPCC:AR6/WGIII/Chapter-7 (section)

=== 7.2.1 Total Net GHG Flux from AFOLU ===

<div id="h2-3-siblings" class="h2-siblings"></div>

National greenhouse gas inventory (NGHGI) reporting following the [[#IPCC--1996|IPCC 1996]] guidelines ( [[#IPCC--1996|IPCC 1996]] ), separates the total anthropogenic AFOLU flux into: (i) net anthropogenic flux from Land Use, Land-Use Change, and Forestry (LULUCF) due to both change in land cover and land management; and (ii) the net flux from Agriculture. While fluxes of CO 2 ( [[#7.2.2|Section 7.2.2]] ) are predominantly from LULUCF and fluxes of CH 4 and N 2 O ( [[#7.2.3|Section 7.2.3]] ) are predominantly from agriculture, fluxes of all three gases are associated with both sub-sectors. However, not all methods separate them consistently according to these sub-sectors, thus here we use the term AFOLU, separate by gas and implicitly include CO 2 emissions that stem from the agriculture part of AFOLU, though these account for a relatively small portion.

Total global net anthropogenic GHG emissions from AFOLU were 11.9 ± 4.4 GtCO 2 -eq yr –1 on average over the period 2010–2019, around 21% of total global net anthropogenic GHG emissions (Table 7.1 and Figure 7.3, using the sum of bookkeeping models for the CO 2 component). When using FAOSTAT/NGHGIs CO 2 flux data, then the contribution of AFOLU to total emissions amounts to 13% of global emissions.

'''Table 7.1 | Net anthropogenic emissions (annual averages for''' '''2010–2019''' a ''') from Agriculture, Forestry and Other Land Use (AFOLU).''' For context, the net flux due to the natural response of land to climate and environmental change is also shown for CO 2 in column E. Positive values represent emissions, negative values represent removals.

{| class="wikitable"
|-
! colspan="6"| '''Anthropogenic'''

! '''Natural response'''

! '''Natural and anthropogenic'''

|-
! '''Gas'''

! '''Units'''

! '''AFOLU Net anthropogenic emissions''' h

! '''Non-AFOLU anthropogenic GHG emissions''' d, f

! '''Total net anthropogenic emissions (AFOLU + non-AFOLU)'''

'''by gas'''

! '''AFOLU as a % of total net anthropogenic emissions by gas'''

! '''Natural land sinks including natural response of land to anthropogenic environmental change and climate variability''' e

! '''Net land- atmosphere CO''' 2 '''flux (i.e., anthropogenic AFOLU + natural fluxes across entire land surface'''

|-
!
! '''A'''

! '''B'''

! '''C = A+B'''

! '''D = (A/C) *100'''

! '''E'''

! '''F=A+E'''

|-
| '''CO''' 2

| GtCO 2 -eq yr –1

| 5.9 ± 4.1 b, f (book-keeping models, managed soils and pasture).

0 to 0.8 (NGHGI/ FAOSTAT data)

| 36.2 ± 2.9

| 42.0 ± 29.0

| 14%

| '''–12.5 ± 3.2'''

| '''–6.6 ± 4.6'''

|-
| rowspan="2"| '''CH''' 4

| MtCH 4 yr –1

| 157.0 ± 47.1 c

| 207.5 ± 62.2

| 364.4 ± 109.3

|
| – i

|
|-
| GtCO 2 -eq yr –1

| 4.2 ± 1.3 g

| 5.9 ± 1.8

| 10.2 ± 3.0

| 41%

|
|-
| rowspan="2"| '''N''' 2 '''O'''

| MtN 2 O yr –1

| 6.6 ± 4.0 c

| 2.8 ± 1.7

| 9.4 ± 5.6

|
|-
| GtCO 2 -eq yr –1

| 1.8 ± 1.1 g

| 0.8 ± 0.5

| 2.6 ± 1.5

| 69%

|
|-
| '''Total''' j

| GtCO 2 -eq yr –1

| 11.9 ± 4.4

(CO 2 component based on book-keeping models, managed soils and pasture)

| 44 ± 3.4

| 55.9 ± 6.1

| 21%

|
|}

a Estimates are given until 2019 as this is the latest date when data are available for all gases, consistent with Chapter 2, this report. Positive fluxes are emission from land to the atmosphere. Negative fluxes are removals.

b Net anthropogenic flux of CO 2 are due to land-use change such as deforestation and afforestation and land management, including wood harvest and regrowth, peatland drainage and fires, cropland and grassland management. Average of three bookkeeping models ( [[#Hansis--2015|Hansis et al. 2015]] ; [[#Houghton--2017|Houghton and Nassikas 2017]] ; [[#Gasser--2020|Gasser et al. 2020]] ), complemented by data on peatland drainage and fires from FAOSTAT ( [[#Prosperi--2020|Prosperi et al. 2020]] ) and GFED4s ( [[#van%20der%20Werf--2017|van der Werf et al. 2017]] ). Bookkeeping based CO 2 -LULUCF emissions (5.7±4.0) are consistent with AR6 WGI and [[IPCC:Wg3:Chapter:Chapter-2|Chapter 2]] of this report. The value of 5.9(±4.1) includes CO 2 emissions from urea application to managed soils and pasture. Comparisons with other estimates are discussed in 7.2.2. Based on NGHGIs and FAOSTAT, the range is 0 to 0.8 GtCO 2 yr –1 .

c CH 4 and N 2 O emission estimates and assessed uncertainty of 30 and 60% respectively, are based on Emissions Database for Global Atmospheric Research (EDGAR) data ( [[#Crippa--2021|Crippa et al. 2021]] ) in accordance with Chapter 2, this report (Sections 2.2.1.3 and 2.2.1.4). Both FAOSTAT ( [[#Tubiello--2019|Tubiello 2019]] ; [[#USEPA--2019|USEPA 2019]] ; [[#FAO--2021a|FAO 2021a]] ) and the USA EPA ( [[#USEPA--2019|USEPA 2019]] ) also provide data on agricultural non-CO 2 emissions, however, mean global CH 4 and N 2 O values considering the three databases are within the uncertainty bounds of EDGAR. EDGAR only considers agricultural and not overall AFOLU non-CO 2 emissions. Agriculture is estimated to account for approximately 89 and 96% of total AFOLU CH 4 and N 2 O emissions respectively. See [[#7.2.3|Section 7.2.3]] for further discussion.

d Total non-AFOLU emissions are the sum of total CO 2 -eq emissions values for energy, industrial sources, waste and other emissions with data from the Global Carbon Project for CO 2 , including international aviation and shipping, and from the PRIMAP database for CH 4 and N 2 O averaged over 2007–2014, as that was the period for which data were available.

e The modelled CO 2 estimates include natural processes in vegetation and soils and how they respond to both natural climate variability and to human-induced environmental changes, for example, the response of vegetation and soils to environmental changes such as increasing atmospheric CO 2 concentration, nitrogen deposition, and climate change (indirect anthropogenic effects) on both managed and unmanaged lands . The estimate shown represents the average from 17 Dynamic Global Vegetation Models with 1SD uncertainty ( [[#Friedlingstein--2020|Friedlingstein et al. 2020]] ).

f The NGHGIs take a different approach to calculating ‘anthropogenic’ CO 2 fluxes than the models ( [[#7.2.2|Section 7.2.2]] ). In particular the sinks due to environmental change (indirect anthropogenic fluxes) on managed lands are generally treated as anthropogenic in NGHGIs and non-anthropogenic in models such as bookkeeping and IAMs. A reconciliation of the results between IAMs and NGHGIs is presented in Cross-Chapter Box 6 in this chapter. If applied to this table, it would transfer approximately –5.5 GtCO 2 yr –1 (a sink) from Column E (which would become –7.0 GtCO 2 yr –1 ) to Column A (which would then be 0.4 GtCO 2 yr –1 ).

g All values expressed in units of CO 2 -eq are based on IPCC AR6 100-year Global Warming Potential (GWP100) values with climate-carbon feedbacks (CH 4 = 27, N 2 O = 273) (Chapter 2, Supplementary Material 2.SM.3; IPCC AR6 WGI [[#7.6|Section 7.6]] ).

h For assessment of cross-sector fluxes related to the food sector, see Chapter 12.

i While it is acknowledged that soils are a natural CH 4 sink ( [[#Jackson--2020|Jackson et al. 2020]] ) with soil microbial removals estimated to be 30 ± 19 MtCH 4 yr –1 for the period 2008–2017 (according to bottom-up estimates), natural CH 4 sources are considerably greater (371 (245–488) MtCH 4 yr –1 ) resulting in natural processes being a net CH 4 source (IPCC AR6 WGI [[IPCC:Wg3:Chapter:Chapter-5#5.2.2|Section 5.2.2]] ). The soil CH 4 sink is therefore omitted from Column E.

j Total GHG emissions concerning non-AFOLU sectors and all sectors combined (Columns B and C) include fluorinated gases in addition to CO 2 , CH 4 and N 2 O. Therefore, total values do not equal the sum of estimates for CO 2 , CH 4 and N 2 O.

<div id="_idContainer011" class="_idGenObjectStyleOverride-1"></div>

[[File:861e472c2e2c2f7ec3261677a162c001 IPCC_AR6_WGIII_Figure_7_3.png]]

'''Figure 7.3 | Subdivision of the total AFOLU emissions from Table 7.''' '''1 by activity and gas for the period 1990 to 2019.''' Positive values are emissions from land to atmosphere, negative values are removals. Panel A shows emissions divided into major activity and gases. Note that ‘biomass burning’ is only the burning of agriculture residues in the fields. The indicated growth rates between 1990–2000, 2000–2010, 2010–2019 are annualised across each time period. Panel B illustrates regional emissions in the years 1990, 2000, 2010, 2019 AFOLU CO 2 (green shading) represents all AFOLU CO 2 emissions. It is the mean from three bookkeeping models ( [[#Hansis--2015|Hansis et al. 2015]] ; [[#Houghton--2017|Houghton and Nassikas 2017]] ; [[#Gasser--2020|Gasser et al. 2020]] ) as presented in the Global Carbon Budget ( [[#Friedlingstein--2020|Friedlingstein et al. 2020]] ) and is not directly comparable to LULUCF in NGHGIs ( [[#7.2.2|Section 7.2.2]] ) ''.'' Data on CH 4 and N 2 O emissions are from the EDGAR database ( [[#Crippa--2021|Crippa et al. 2021]] ). See Sections 7.2.2 and 7.2.3 for comparison of different datasets. All values expressed are as CO 2 -eq with GWP100 values: CH 4 = 27, N 2 O = 273.

This AFOLU flux is the net of anthropogenic emissions of CO 2 , CH 4 and N 2 O, and anthropogenic removals of CO 2 . The contribution of AFOLU to total emissions varies regionally with highest in Latin America and Caribbean with 58% and lowest in Europe and North America with each 7% (Chapter 2, [[IPCC:Wg3:Chapter:Chapter-2#2.2.3|Section 2.2.3]] ). There is a discrepancy in the reported CO 2 AFOLU emissions magnitude because alternative methodological approaches that incorporate different assumptions are used ( [[#7.2.2.2|Section 7.2.2.2]] ). While there is ''low agreement'' in the trend of global AFOLU CO 2 emissions over the past few decades ( [[#7.2.2|Section 7.2.2]] ), they have remained relatively constant ( ''medium confidence'' ) (Chapter 2). Average non-CO 2 emission (aggregated using GWP100 IPCC AR6 values) from agriculture have risen from 5.2 ± 1.4 GtCO 2 -eq yr –1 for the period 1990 to 1999, to 6.0 ± 1.7 GtCO 2 -eq yr –1 for the period 2010 to 2019 ( [[#Crippa--2021|Crippa et al. 2021]] ) ( [[#7.2.3|Section 7.2.3]] ).

To present a fuller understanding of land–atmosphere interactions, Table 7.1 includes an estimate of the natural sink of land to atmospheric CO 2 ( [[#Jia--2019|Jia et al. 2019]] ) (IPCC AR6 WGI Chapter 5). Land fluxes respond naturally to human-induced environmental change (e.g., climate change, and the fertilising effects of increased atmospheric CO 2 concentration and nitrogen deposition), known as ‘indirect anthropogenic effects’, and also to ‘natural effects’ such as climate variability ( [[#IPCC--2010|IPCC 2010]] ) (Table 7.1 and [[#7.2.2|Section 7.2.2]] ). This showed a removal of –12.5 ± 3.2 GtCO 2 yr –1 ( ''medium confidence'' ) from the atmosphere during 2010–2019 according to global dynamic global vegetation model (DGVM) models ( [[#Friedlingstein--2020|Friedlingstein et al. 2020]] ) 31% of total anthropogenic net emissions of CO 2 from all sectors. It is likely that the NGHIs and FAOSTAT implicitly cover some part of this sink and thus provide a net CO 2 AFOLU balance with some 5 GtCO 2 lower net emissions than according to bookkeeping models, with the overall net CO 2 value close to being neutral. Model results and atmospheric observations concur that, when combining both anthropogenic (AFOLU) and natural processes on the entire land surface (the total ‘land–atmosphere flux’), the land was a global net sink for CO 2 of –6.6 ± 4.6 GtCO 2 yr –1 with a range for 2010 to 2019 from –4.4 to –8.4 GtCO 2 yr –1 . ( [[#Rödenbeck--2003|Rödenbeck et al. 2003]] , 2018; [[#Chevallier--2005|Chevallier et al. 2005]] ; [[#Feng--2016|Feng et al. 2016]] ; [[#van%20der%20Laan-Luijkx--2017|van der Laan-Luijkx et al. 2017]] ; [[#Niwa--2017|Niwa et al. 2017]] ; [[#Patra--2018|Patra et al. 2018]] ). The natural land sink is ''highly likely'' to be affected by both future AFOLU activity and climate change (IPCC AR6 WGI Box 5.1 and Figure SPM. 7), whereby under more severe climate change, the amount of carbon stored on land would still increase although the relative share of the emissions that land takes up, declines.

<div id="7.2.2" class="h2-container"></div>

<span id="flux-of-co-2-from-afolu-and-the-non-anthropogenic-land-sink"></span>