Thread:Comments:UN Report on Global Warming calls for rapid 'unprecedented' changes globally to limit planetary warming to 1.5 degree C/the 'new' U.N. report (2)

Just an FYI; the 'new U.N. report' that has prompted a flurry of political messages (even ones that may be personally appealing) is no longer an authoritative communication from IPCC. These various interim reports are not the Assessment Reports required by the UN Climate Convention. Group I (the natural science authority) has never concluded a cause for the general temperature rise in the 20th century but has remained, until AR5, " . . . confident that the CO2 signal will emerge . . .". They waited over 30 years. This 'new report' is PR from the policy side based on the old CMIP5 (CMIP5 = Coupled Model Inter-comparison Project on Climate Change, Report 5) that supported IPCC AR5 from 2013-14. IPCC AR6, that will carry the full endorsement of Group I, is due in 2022. CMIP6 was finalized at the end of 2017 and can be reviewed here: www.geosci-model-dev.net/10/2247/2017/gmd-10-2247-2017.pdf. A look at the abstract will reveal why the AR6 is delayed until 2022 (rather than the original 5 year rule). "Staying ahead of the curve" with mitigation and adaptation policies for possible future events seems prudent; over-commitment to an outcome not yet demonstrated to be actual is not. The science is in progress - reading beyond the 'Executive Summary' is important. Realizing that few will want to read a long paper, here is a pertinent paragraph from the conclusions section of the CMIP6 paper cited above. "6.3 Future forcing scenarios

In CMIP5, future solar irradiances assumed no long-term changes in the Sun and were obtained by simply repeating solar cycle 23 into the future. In CMIP6, we include a more realistic evolution for future solar forcing based on the weighted average of three statistical models constrained by past long-term solar proxy data; this shows a moderate decrease to a Gleissberg-type level of solar activity until 2100 for the REF scenario. We ignore scenarios with high levels of solar activity because the Sun just left such an episode (called a grand solar maximum), and several studies suggest that it is very unlikely to return to it in the next 300 years. In addition, we provide an EXT scenario for the future that can be used for sensitivity studies, which includes an evolution to an exceptionally low level of solar activity during the 21st century similar to that estimated for the Maunder Minimum."

Why should we think that Group I would make such a major addition to the 'grand inter-coupled model' if the old model yielded the material equivalence required for a valid conclusion?