Editing IPCC:AR6/WGIII/Chapter-4 (section)

==== 4.2.2.5 Estimated Impact of New and Updated NDCs on Emissions Projections ====

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The number of studies estimating the emissions implications of new and updated NDCs and announced mitigation pledges that can be used for the quantitative assessment is limited to four (Table 4.3) ( [[#Climate%20Action%20Tracker--2021|Climate Action Tracker 2021]] ; [[#den%20Elzen--2021|den Elzen et al. 2021]] ; [[#Meinshausen--2021|Meinshausen et al. 2021]] ; [[#JRC--2021|JRC 2021]] ). One other study includes a limited number of NDC updates ( [[#Riahi--2021|Riahi et al. 2021]] ) and another ( [[#UNFCCC--2021|UNFCCC 2021]] ) excludes LULUCF emissions. They are therefore not directly comparable to the other two. In addition, the UNEP Emissions Gap Report 2021 ( [[#UNEP--2021|UNEP 2021]] ) in itself is assessment of almost the same studies included here. The evidence base for the updated NDC assessment is thus considerably smaller compared to that of the assessment of emissions implications of original NDCs presented in Section 4.2.2.3. However, it is worthwhile to note that the earlier versions of the studies summarised in Table 4.2 and Table 4.3 are broadly representative for the emissions range implied by the pre-COVID-19 current policies and original NDCs of the full set of studies shown in Table 4.1, therefore building confidence in estimates.

An additional challenge lies in the fact that these studies do not all apply the same cut-off date for NDC updates, potentially leading to larger systematic deviations in the resulting emission estimates. Another complication is the fact that publicly announced mitigation pledges on global 2030 emissions that have not been officially submitted to the UNFCCC NDC registry yet, have been included in several of the studies to anticipate their impact on emission levels (see notes to [[#_idTextAnchor044|Table 4.3]] ). In addition to the updates of NDC targets, most of the new studies also include impacts of COVID-19 on future emission levels (as discussed in Section ) which may have led to considerable downward revisions of emission trends unrelated to NDCs. Table 4.3 presents the emission estimates of the four studies that form the basis of the quantitative assessment presented here and three other studies to compare with.

Comparing the emission levels implied by the new and updated NDCs as shown in Table 4.3 with those estimated by the original NDCs from the same studies (as included in Table 4.1), a downward revision of 3.8 (3.0–5.3) GtCO 2 -eq of the central unconditional NDC estimates and of 4.5 (2.7–6.3) GtCO 2 -eq of the central conditional NDC estimate emerges ( ''medium evidence'' , ''medium agreement'' ). The emissions gaps between temperature limits and new and updated NDCs are assessed in Cross-Chapter Box 4 below. New and updated unconditional NDCs reduce the median gap with emissions pathways that limit warming to 2°C (&gt;67%) in 2030 by slightly more than 20%, from a median gap of 17 GtCO 2 -eq (9–23) to 13 (10–16). New and updated conditional NDCs reduce the median gap with emissions pathways that limt warming to 2°C (&gt;67%) in 2030 by about one third, from 14 GtCO 2 -eq (10–20) to 9 (6–14). New and updated unconditional NDCs reduce the median gap with emissions pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot in 2030 by about 15%, from a median gap of 27 GtCO 2 -eq (19–32) to 22 GtCO 2 -eq (19–26). New and updated conditional NDCs reduce the median gap with emissions pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot in 2030 by about 20%, from a median gap of 24 GtCO 2 -eq (20–29) to 19 GtCO 2 -eq (16–23). Box 4.1 discusses the adaptation gap.

Globally, the implementation gap between projected emissions of current policies and the unconditional and conditional new and updated NDCs is estimated to be around 4 and 7 GtCO 2 -eq in 2030, respectively ( ''medium evidence'' , ''medium agreement'' ) (Tables 4.2 and 4.3), with many countries requiring additional policies and associated climate action to meet their mitigation targets as specified under the NDCs ( ''limited evidence'' ) (Section 4.2.2.6). It should be noted that the implementation gap varies considerably across countries, with some having policies in place estimated to be sufficient to achieve the emission targets their NDCs, some where additional policies may be required to be sufficient, as well as differences between the policies in place and action on the ground.

'''Table 4.3 | Projected global GHG emissions of new and update''' '''d NDCs by 2030.'''

{| class="wikitable"
|-
! rowspan="3"| Study

! rowspan="3"| Cut-off date

! colspan="4"| Kyoto GHGs a [GtCO 2 -eq]

! rowspan="3"| References

|-
! colspan="2"| Historical

! colspan="2"| Median (min–max) b 2030

|-
! 2015

! 2019

! Unconditional NDCs

! Conditional NDCs

|-
| Climate Action Tracker c

| 5/2021

| 51

| 52

| 50

| 47

| [[#Climate%20Action%20Tracker--2021|Climate Action Tracker (2021)]]

|-
| PBL d

| 9/2021

| 52

| 54

| 53 (51–55)

| 52 (49–53)

| [[#den%20Elzen--2021|den Elzen et al. (2021)]] ; [[#Nascimento--2021|Nascimento et al. (2021)]]

|-
| JRC – GECO e

| 10/2021

| 51

|
| 48

| [[#JRC--2021|JRC (2021)]]

|-
| Meinshausen et al. f

| 10/2021

| 54

| 56

| 55 (54–57)

| 53 (52–55)

| [[#Meinshausen--2021|Meinshausen et al. (2021)]]

|-
| Total g

|
| colspan="2"|
| 53 (50–57)

| 50 (47–55)

|
|-
| colspan="6"| '''Other studies for comparison'''

|
|-
| UNEP EGR h

| 9/2021

| colspan="2"|
| 53 (50–55)

| 50 (47–53)

| [[#UNEP--2017a|UNEP (2017a)]]

|-
| UNFCCC Secretariat i

| 7/2021

| colspan="2"|
| 57 (55–58)

| 54 (52–56)

| [[#UNFCCC--2021|UNFCCC (2021)]]

|-
| ENGAGE j

| 3/2021

| colspan="2"|
|
| 51 (49–53)

| [[#Riahi--2021|Riahi et al. (2021)]]

|}

Notes: a GHG emissions expressed in CO 2 -eq emission using AR6 100-year GWPs. GHG emissions from studies that provide aggregate GHG emissions using other GWPs are rescaled using 2019 GHG emissions from [[IPCC:Wg3:Chapter:Chapter-2|Chapter 2]] ( [[#Minx--2021|Minx et al. 2021]] ; [[#Crippa--2021|Crippa et al. 2021]] ). Note that due to slightly different system boundaries across historical emission datasets as well as data uncertainties (Chapter 2, SM2.2) relative change compared to historical emissions should be calculated vis-à-vis the historical emissions data used by a particular study. b If a range is available from a study, a median is provided in addition to the range. c Announced mitigation pledges on global 2030 emissions of China and Japan included. d Announced mitigation pledges of China, Japan, Republic of Korea included. e Announced mitigation pledge of Korea not included. f Announced mitigation pledges of China and Republic of Korea not included, emissions from international aviation and shipping not included. g Ranges across four studies are calculated using the median and the full range including the minimum and maximum of studies if available. h UNEP EGR 2021 estimate listed for comparison, but since largely relying on the same studies not included in range estimate. i NDCs submitted until 30 July included, announcements not included, excluding LULUCF emissions. j NDC updates of Brazil, EU and announcement of China included as a sensitivity analysis compared to original NDCs.

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