The IPCC knows they have lost credibility for many reasons and by pretending that HAAD does not exist. The skeptics also lose credibility for the same reason despite coming from behind with a hollow victory by also ignoring the obvious HAAD operation.
By failing to consider all the known variables outside of CO2, neither side can claim a hypothesis, that can be disproved, actually exists.
Even as the words are in need of decoding, it appears the work group is pointing to globally observed HAAD operation as an excuse for the completely failed AGW hypothesis.
Clear language is used to deny that geoengineering via solar radiation management (SRM) has yet been deployed for the purpose of mitigating global warming/climate change.
P 871: “SRM methods are unimplemented and untested. Research on SRM is in its infancy though it leverages understanding of how the climate responds to forcing more generally.”
It appears the work group wants to make it clear that the publicly observed HAAD are not officially coordinated by any UN entity but leaves it to your imagination as to who is in charge and how the massive aerosol dumps are making it impossible for the hypothesis to fit the observed data. That the IPCC has no control over HAAD is no surprise to observers who’ve regarded aerosol dumps as a military operation long before emergency SRM geoengineering was thought necessary.
The executive summary is a bold admission that the IPCC has little idea how cloud/aerosol chemistry effects observations:
P 869: “Clouds and aerosols continue to contribute the largest uncertainty to estimates and interpretations of the Earth’s changing energy budget.”
A tone of “activism” to cease the HAAD operation and reject SRM is apparent in this comment on geoengineering proposals. The risks include drought-forcing, polar ozone depletion (Increased UVB penetration to melt ice), consequences of addictive SRM increases to maintain status-quo and continued increases in ocean acidification.
P 871: Numerous side effects, risks and shortcomings from SRM have been identified. Several lines of evidence indicate that SRM would produce a small but significant decrease in global precipitation (with larger differences on regional scales) if the global surface temperature were maintained. A number of side effects have been identified. One that is relatively well characterised is the likelihood of modest polar stratospheric ozone depletion associated with stratospheric aerosol SRM. There could also be other as yet unanticipated consequences. As long as greenhouse gas concentrations continued to increase, the SRM would require commensurate increase, exacerbating side effects. Additionally, scaling SRM to substantial levels would carry the risk that if the SRM were terminated for any reason, there is high confidence that surface temperatures would increase rapidly (within a decade or two) to values consistent with the greenhouse gas forcing, which would stress systems sensitive to the rate of climate change. Finally, SRM would not compensate for ocean acidification from increasing CO2. [7.6.3, 7.7, Figures 7.22–7.24]
“To destroy the ozone layer and hence increase abruptly the surface temperature of the Earth, by spraying “several hundred thousand tons of chlorine or bromine” with a stratospheric airplane. Fleming, 2007(a), pp. 56-57; Fleming, 2007(b), “note n° viii” p. 9 & p. 5 (source)”
Following the 2007 IPCC report, data pointing to the significant role of atmospheric aerosols began entering the climate change discussion.