Tallbloke's Talkshop
The 6th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR6) concluded “It is very likely that well-mixed GHGs [greenhouse gases] were the main driver of tropospheric warming since 1979” (IPCC, 2021; p.5). This statement implies that all known climate forcings have properly been evaluated using the available data, and GHGs have been found to exert a disproportionally large radiative effect on the Global Surface Air Temperature (GSAT) over the past 45 years. However, a close examination of Chapter 7 of the Working Group I (WG1) Contribution to the IPCC AR6 (Forster et al. 2021), which discusses the Earth’s energy budget, climate feedbacks and climate sensitivity, reveals that the observed decrease of Earth’s albedo and the corresponding increase of absorbed shortwave radiation by the Planet for the past 20 years have not been taken into account as contributors to the recent warming. Section 7.2.2 of Chapter 7 entitled “Changes in Earth’s Energy Budget” acknowledges that there have been multidecadal periods of significant decreasing and increasing trends in surface solar radiation (SSR) called “global dimming” (i.e. from 1950s to 1980s) and “global brightening” (after 1980s), respectively. The report states: “There is high confidence that these [SSR] trends are widespread, and not localized phenomena or measurement artefacts.” Indeed, the existence of such dimming and brightening multidecadal periods has been acknowledged by science for more than 10 years (Stanhill et al. 2014; Yuan et al. 2021), but the IPCC AR6 provides no global estimate of the observed positive trend in SSR since 1980s and its impact on GSAT. Instead, the Report simply states “The origin of these trends is not fully understood”.
With respect to the top-of-the-atmosphere (TOA) solar fluxes, Section 7.2.2 of the IPCC AR WG1 offers no analysis of the substantial decrease in Earth’s shortwave reflectance since 2000 observed by the NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project (Loeb et al. 2018, 2019, 2020 and 2021) and also reported by other research teams (e.g. Dübal & Vahrenholt 2021; Stephens et al. 2022). The Report does not discuss the observed 2.0 W m-2 increase in solar-energy uptake by the Planet from 2000 to 2020 nor its contribution to the recent warming. What is even more puzzling, Subsection 7.2.2.1 of the IPCC AR6 WG1 Contribution features graphs in their Fig. 7.3 (on p. 936) showing an increasing reflected solar flux and decreasing outgoing thermal flux since 2000 that are supposedly based on CERES data. However, these trends are opposite of what CERES has actually measured and directly contradict results reported by prior studies. This article presents findings from our investigation of Fig. 7.3 in the IPCC AR6.
