Solar forcing may have a 4 to 7 times greater effect on climate change than current climate models indicate, which may mean modern climate change is predominantly natural rather than anthropogenic.
Anthropogenic global warming (AGW) attribution may be significantly dependent on the choice of dataset.
Advocates of AGW may only use Total Solar Irradiance (TSI) reconstructions that align with the perspective that the Sun has little to no impact on climate. Consequently, climate models may only use the PMOD’s model-based satellite data (which shows a declining trend since 1980) rather than the ACRIM (which shows an increasing TSI trend from the 1980s to 2000s).
The biased selection of long-term TSI reconstructions that show little to no variability are also preferred over TSI reconstructions with large variability. For example, the uncertainty in the estimate of the increase in TSI since the Maunder Minimum (1645-1715) ranges anywhere from 0.75 W/m² to 6.3 W/m² (Yeo et al., 2020). AGW advocates will, of course, select the lowest TSI change value (0.75 W/m²) and reject the higher values (6.3 W/m²), as then it is much easier to attribute modern warming to anthropogenic activity rather than to solar forcing.
The IPCC has selected one TSI dataset in the latest (2021) report for its global warming attribution assessments and climate models (GCMs). The dataset of course aligns only with the view modern warming is human-caused, and not natural, and thus it depicts a declining TSI trend since 1980 (PMOD) and almost no variability since the Maunder Minimum.
A new study (Connolly et al., 2023 with press release) identifies 27 other TSI estimates (purposely) ignored by the IPCC, several of which suggest modern warming may be up to 71-87% natural – especially if the temperature stations that do not show a strong artificial urban warming bias are used.
“Several of these different solar activity estimates suggest that most of the warming observed outside urban areas (in rural areas, oceans, and glaciers) could be explained in terms of the Sun.”
Image Source: Connolly et al., 2023 and press release
Another new study (Scafetta, 2023) suggests the Sun’s real climate impact may be 4-7 times larger than just from TSI (radiative) forcing alone, as the solar activity variations may mechanistically affect cloud albedo, which has been observed to drive 1-3 W/m² per decade changes in shortwave forcing (McLean, 2014).
“Thus, at least about 80% of the solar influence on the climate could be generated by processes other than direct TSI forcing.”
Climate models do not allow for any solar influence beyond the small, flat radiative forcing changes associated with TSI forcing, as this way it can be claimed that natural factors have little to no bearing on climate change.
Alternative solar activity records, as shown in TSI #2 Model below, have the Sun’s total impact directly linked to global temperature changes, including for recent decades.