by R. McKitrick and J. Christy, July 6, 2018 in AGU100

Abstract

Overall climate sensitivity to CO2

doubling in a general circulation model results from a complex

system of parameterizations in combination with the underlying model structure. We refer to this as the model’smajor hypothesis, and we assume it to be testable. We explain four criteria that a valid test should meet: measurability, specificity, independence, and uniqueness. We argue that temperature change in the

tropical 200- to 300-hPa layer meets these criteria. Comparing modeled to observed trends over the past

60 years using a persistence-robust variance estimator shows that all models warm more rapidly than

observations and in the majority of individual cases the discrepancy is statistically significant. We argue that

this provides informative evidence against the major hypothesis in most current climate models.

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