If the error and uncertainty associated with determining the extent to which natural factors (aerosol forcing, downwelling shortwave variability) affect climate are factors of ten times larger than the presumed effects of human activity, then we cannot definitively say human activity is driving climate change.
It takes 10 years and 22 ppm for CO2 forcing to allegedly deliver a total additional radiative impact of 0.2 W/m² at the surface (Feldman et al., 2015). So after about 50 years and 110 ppm an additional 1 W/m² climate impact may be assessed for the Earth’s radiation budget.
The direct aerosol radiative effects (ADREs) in a clear-sky atmosphere affecting Earth’s top-of-atmosphere (TOA) and surface radiation imbalances are predominantly derived from natural, not anthropogenic, sources (Kremser et al., 2016, Neely et al., 2013).
And, per a new study, the global-scale errors in calculating these ADREs at the global surface amounts to −4.78 ± 2.2 W/m². This calculation error estimate is thus 24 times larger than the presumed surface forcing from CO2 over a 10-year period (0.2 W/m²). This alone effectively rules out the determination of human activity, or CO2 emissions, as the driver of climate.
Image Source: Shi et al., 2022
It gets worse. Another new study identifies the uncertainty in calculating radiative fluxes at the surface (Arctic) as ranging from 12 to 16 W/m². These uncertainty (overestimating and/or underestimating the forcing) values are about 60 to 80 times larger than the surface forcing from CO2 over a 10-year span.
Once again, this precludes the attribution of CO2 forcing as the driver of climate changes in the Arctic.