Explosive Reality Behind Climate: Accelerating Uncertainty of Clouds
It turns out that uncertainties in the energetic responses of Earth climate systems are more than 10 times larger than the entire energetic effect of increased CO2.15 If the uncertainty is larger than the effect, the effect itself becomes moot. If the effect itself is debatable, then what is the IPCC talking about? And from where comes the certainty of a large CO2 impact on climate? _Skeptic_via_WUWT
The difficulty is serious even over short times. The inset to Figure 4 shows that after only 20 years, the uncertainty from cloud error is ±22° and for forcing, it’s ±3°. The effect of the ~1% forcing uncertainty alone tells us that a 99% accurate GCM couldn’t discern a new Little Ice Age from a major tropical advance from even 20 years out. Not only are these physical uncertainties vastly larger than the IPCC allows in Figure SPM-5 (Figure 1), but the uncertainties the IPCC allows in Figure SPM-5 aren’t even physical.16
When both the cloud and the forcing uncertainties are allowed to accumulate together, after 5 years the A2 scenario includes a 0.34°C warmer Earth but a ±8.8°C uncertainty. At 10 years this becomes 0.44±15° C, and 0.6±27.7°C in 20 years. By 2100, the projection is 3.7±130°C. From clouds alone, all the IPCC projections have uncertainties that are very much larger than the projected greenhouse temperature increase. What is credible about a prediction that sports an uncertainty 20–40 times greater than itself? After only a few years, a GCM global temperature prediction is no more reliable than a random guess. That means the effect of greenhouse gasses on Earth climate is unpredictable, and therefore undetectable. And therefore moot.
The rapid growth of uncertainty means that GCMs cannot discern an ice age from a hothouse from 5 years away, much less 100 years away. So far as GCMs are concerned, Earth may be a winter wonderland by 2100 or a tropical paradise. No one knows. _Skeptic_via_Wattsupwiththat