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==== 7.3.2.7 Synthesis ==== <div id="h3-10-siblings" class="h3-siblings"></div> The ERF of GHGs (excluding ozone and stratospheric water vapour) over 1750β2019 is assessed to be 3.32 Β± 0.29 W m <sup>β2</sup> . It has increased by 0.49 W m <sup>β2</sup> compared to AR5 (reference year 2011) ( ''high confidence'' ) ''.'' Most of this has been due to an increase in CO <sub>2</sub> concentration since 2011 [0.27 Β± 0.03] W m <sup>β2</sup> , with concentration increases in CH <sub>4</sub> , N <sub>2</sub> O and halogenated compounds adding 0.02, 0.02 and 0.01 W m <sup>β2</sup> respectively (Table 7.5). Changes in the radiative efficiencies (including adjustments) of CO <sub>2</sub> , CH <sub>4</sub> , N <sub>2</sub> O and halogenated compounds have increased the ERF by an additional 0.15 W m <sup>β2</sup> compared to the AR5 values ( ''high confidence'' ). Note that the ERFs in this section do not include chemical effects of GHGs on production or destruction of ozone or aerosol formation (Section 6.2.2). The ERF for ozone is considerably increased compared to AR5 due to an increase in the assumed ozone precursor emissions in CMIP6 compared to CMIP5, and better accounting for the effects of both ozone precursors and ODSs in the stratosphere. The ERF for stratospheric water vapour is slightly reduced. The combined ERF from ozone and stratospheric water vapour has increased since AR5 by 0.10 Β± 0.50 W m <sup>β2</sup> ( ''high confidence'' ), although the uncertainty ranges still include the AR5 values. <div id="_idContainer025" class="Basic-Text-Frame"></div> '''Table 7.5''' '''|''' '''Present-day mole fractions in parts per trillion (pmol mol''' β1 '''), except where specified, and effective radiative forcing (ERF, in W m''' β2 ''') for the well-mixed greenhouse gases (WMGHGs).''' Data taken from ( [[IPCC:Wg1:Chapter:Chapter-2|Chapter 2]] [[IPCC:Wg1:Chapter:Chapter-2#2.2.3|Section 2.2.3]] ). The data for 2011 (the time of the AR5 estimates) are also shown. Some of the concentrations vary slightly from those reported in AR5 owing to averaging different data sources. Individual species are reported where 1750β2019 ERF is at least 0.001 W m <sup>β2</sup> . Radiative efficiencies for the minor gases are given in Supplementary Material, Table 7.SM.7. Uncertainties in the ERF for all gases are dominated by the uncertainties in the radiative efficiencies. Tabulated global mixing ratios of all WMGHGs and ERFs from 1750 to 2019 are provided in Annex III. {| class="wikitable" |- | | colspan="4"| Concentration | colspan="2"| ERF with Respect to 1850 | colspan="2"| ERF with Respect to 1750 |- | | 2019 | 2011 | 1850 | 1750 | 2019 | 2011 | 2019 | 2011 |- | CO <sub>2</sub> (ppm) | 409.9 | 390.5 | 285.5 | 278.3 | 2.012 Β± 0.241 | 1.738 | 2.156 Β± 0.259 | 1.882 |- | CH <sub>4</sub> (ppb) | 1866.3 | 1803.3 | 807.6 | 729.2 | 0.496 Β± 0.099 | 0.473 | 0.544 Β± 0.109 | 0.521 |- | N <sub>2</sub> O (ppb) | 332.1 | 324.4 | 272.1 | 270.1 | 0.201 Β± 0.030 | 0.177 | 0.208 Β± 0.031 | 0.184 |- | HFC-134a | 107.6 | 62.7 | 0.0 | 0.0 | 0.018 | 0.010 | 0.018 | 0.010 |- | HFC-23 | 32.4 | 24.1 | 0.0 | 0.0 | 0.006 | 0.005 | 0.006 | 0.005 |- | HFC-32 | 20.0 | 4.7 | 0.0 | 0.0 | 0.002 | 0.001 | 0.002 | 0.001 |- | HFC-125 | 29.4 | 10.3 | 0.0 | 0.0 | 0.007 | 0.002 | 0.007 | 0.002 |- | HFC-143a | 24.0 | 12.0 | 0.0 | 0.0 | 0.004 | 0.002 | 0.004 | 0.002 |- | SF <sub>6</sub> | 10.0 | 7.3 | 0.0 | 0.0 | 0.006 | 0.004 | 0.006 | 0.004 |- | CF <sub>4</sub> | 85.5 | 79.0 | 34.0 | 34.0 | 0.005 | 0.004 | 0.005 | 0.004 |- | C <sub>2</sub> f <sub>6</sub> | 4.8 | 4.2 | 0.0 | 0.0 | 0.001 | 0.001 | 0.001 | 0.001 |- | CFC-11 | 226.2 | 237.3 | 0.0 | 0.0 | 0.066 | 0.070 | 0.066 | 0.070 |- | CFC-12 | 503.1 | 528.6 | 0.0 | 0.0 | 0.180 | 0.189 | 0.180 | 0.189 |- | CFC-113 | 69.8 | 74.6 | 0.0 | 0.0 | 0.021 | 0.022 | 0.021 | 0.022 |- | CFC-114 | 16.0 | 16.3 | 0.0 | 0.0 | 0.005 | 0.005 | 0.005 | 0.005 |- | CFC-115 | 8.7 | 8.4 | 0.0 | 0.0 | 0.002 | 0.002 | 0.002 | 0.002 |- | HCFC-22 | 246.8 | 213.2 | 0.0 | 0.0 | 0.053 | 0.046 | 0.053 | 0.046 |- | HCFC-141b | 24.4 | 21.4 | 0.0 | 0.0 | 0.004 | 0.003 | 0.004 | 0.003 |- | HCFC-142b | 22.3 | 21.2 | 0.0 | 0.0 | 0.004 | 0.004 | 0.004 | 0.004 |- | CCl <sub>4</sub> | 77.9 | 86.1 | 0.0 | 0.0 | 0.013 | 0.014 | 0.013 | 0.014 |- | Sum of HFCs (HFC-134a equivalent) | 237.1 | 128.6 | 0.0 | 0.0 | 0.040 | 0.022 | 0.040 | 0.022 |- | Sum of CFCs+HCFCs+other ozone depleting gases covered by the Montreal Protocol (CFC-12 equivalent) | 1031.9 | 1050.1 | 0.0 | 0.0 | 0.354 | 0.362 | 0.354 | 0.362 |- | Sum of PFCs (CF <sub>4</sub> equivalent) | 109.4 | 98.9 | 34.0 | 34.0 | 0.007 | 0.006 | 0.007 | 0.006 |- | Sum of Halogenated species | | 0.408 Β±0.078 | 0.394 | 0.408 Β±0.078 | 0.394 |- | Total | | 3.118 Β±0.258 | 2.782 | 3.317 Β±0.278 | 2.981 |} <div id="7.3.3" class="h2-container"></div> <span id="aerosols"></span>
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