I´m not a climate scientist, but I´m also concerned, to say the least, about how IPCC considered natural variability:
IPCC used circular reasoning to exclude natural variability. IPCC relied on climate models (CMIP5), the hypotheses under test if you will, to exclude natural variability:
“Observed Global Mean Surface Temperature anomalies relative to 1880–1919 in recent years lie well outside the range of Global Mean Surface Temperature anomalies in CMIP5 simulations with natural forcing only, but are consistent with the ensemble of CMIP5 simulations including both anthropogenic and natural forcing … Observed temperature trends over the period 1951–2010, … are, at most observed locations, consistent with the temperature trends in CMIP5 simulations including anthropogenic and natural forcings and inconsistent with the temperature trends in CMIP5 simulations including natural forcings only.”
(Ref.: Working Group I contribution to fifth assessment report by IPCC. TS.4.2.)
It starts to get really ugly if we combine that logical flaw with the realization by Gavin Schmidt that ” the model simulations are affected by the (partially overestimated) forcing in CMIP5 as well as model responses”
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Mark says:
3 Nov 2015 at 6:41 PM
Apparently Roy Spencer’s CMIP5 models vs observations graph has gotten some “uninformed and lame” criticisms from “global warming activist bloggers,” but no criticism from any “actual climate scientists.” Would any actual climate scientists, perhaps one with expertise in climate models, care to comment? http://www.drroyspencer.com/2015/11/models-vs-observations-plotting-a-conspiracy/
[Response: Happy to! The use of single year (1979) or four year (1979-1983) baselines is wrong and misleading. The use of the ensemble means as the sole comparison to the satellite data is wrong and misleading. The absence of a proper acknowledgement of the structural uncertainty in the satellite data is wrong and misleading. The absence of NOAA STAR or the Po-Chedley et al reprocessing of satellite data is… curious. The averaging of the different balloon datasets, again without showing the structural uncertainty is wrong and misleading. The refusal to acknowledge that the model simulations are affected by the (partially overestimated) forcing in CMIP5 as well as model responses is a telling omission. The pretence that they are just interested in trends when they don’t show the actual trend histogram and the uncertainties is also curious, don’t you think? Just a few of the reasons that their figures never seem to make their way into an actual peer-reviewed publication perhaps… – gavin]
– See more at: http://www.realclimate.org/index.php/archives/2015/11/unforced-variations-nov-2015/#sthash.eIH9lMBG.dpuf
(Gavin Schmidt is Climatologist, climate modeler and Director of the NASA Goddard Institute for Space Studies (GISS) in New York).
The travesty is completed by how models are adjusted to keep them in line with observations:
«When initialized with states close to the observations, models ‘drift’ towards their imperfect climatology (an estimate of the mean climate), leading to biases in the simulations that depend on the forecast time. The time scale of the drift in the atmosphere and upper ocean is, in most cases, a few years. Biases can be largely removed using empirical techniques a posteriori. …»
(Ref: Contribution from Working Group I to the fifth assessment report by IPCC; 11.2.3 Prediction Quality; 11.2.3.1 Decadal Prediction Experiments)
And by how the models model parameters seems to be set ref:
Climate forcings in Goddard Institute for Space Studies SI2000 simulations; J. Hansen et al
“The bottom line is that, although there has been some narrowing of the range of climate sensitivities that emerge from realistic models [Del Genio and Wolf, 2000], models still can be made to yield a wide range of sensitivities by altering model parameterizations. We suggest that the best constraint on actual climate sensitivity is provided by paleoclimate data that imply a sensitivity 3 ± 1°C for 2 CO2 [Hansen et al., 1984, 1993, 1997b; Hoffert and Covey, 1992]. It is satisfying that the a priori sensitivity of the SI2000 model comes out near the middle of the empirical range of 2 – 4°C for 2 CO2. However, for the sake of interpreting observed climate change and predicting future change it is appropriate to consider climate sensitivity as an uncertain parameter that may, in fact, be anywhere within that range.”
“Therefore we include the possibility of altering the model’s climate sensitivity. We do this by adjusting an arbitrary cloud feedback as defined in the appendix of Hansen et al. [1997a]. Specifically, the cloud cover is multiplied by the factor 1 + cT , where T, computed every time step, is the deviation of the global mean surface air temperature from the long-term mean in the model control run at the same point in the seasonal cycle and c is an empirical constant. For the SI2000 second-order model we take c = 0.04 and -0.01 to obtain climate sensitivities of 2°C and 4°C for 2 CO2.”
In my view – the idea that the conclusion by IPCC is substantiated by the considerations that IPCC has actually made is falsified – the idea is wrong. Judgement about United Nations climate theory must be suspended.
