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Pervasive Warming Bias in CMIP6 Tropospheric Layers

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This paper by Ross McKitrick and John Christy examined the first 38 models of CMIP6 over 1979 - 2014. The paper reports that every model overshoots the observed trend in both the lower and mid troposphere, globally and in the tropics. The models as a group warm too much throughout the global atmosphere. “The models with low ECS values tend to have lower tropospheric trends, thus closer to observed values, and therefore are more likely to be realistic.” The observed trends in the lower and mid troposphere are 0.148 °C/decade and 0.091 °C/decade, respectively. The paper’s conclusions state “An ensemble of models with warming rates consistent with observations would likely have to have ECS values at or below the bottom of the CMIP6 range.” The models average global warming trends of the lower and mid troposphere are 1.86 and 2.40 times the observations. The models tropical trends of the lower and mid troposphere are 2.40 and 3.24 times the observations, respectively.



Climate Models Provide unrealistically high projections of future warming

Climate researchers have tested a climate model against geological evidence from a previous warming period called the Early Eocene, a time when rainforests thrived in the tropics of the New World, according to fossil evidence. The CESM2 model (USA) projected Early Eocene land temperatures exceeding 55 °C (131 °F) in the tropics, which is much higher than the temperature tolerance of plant photosynthesis — conflicting with the fossil evidence. This projected temperature would have created lifeless tropical deserts during the Early Eocene, a period of high atmospheric CO2 and abundant tropical life. ScienceDaily reports about the study “On average across the globe, the model projected surface temperatures at least 6 °C (11 °F) warmer than estimates based on geological evidence.”



Models and Rainfall – Four Climate Models Compared

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This article from the website ‘scienceofdoom’ compares global rainfall among the Japanese, German, Canadian and Australian climate models. The first set of four maps compares each model’s rainfall prediction for the moderate emissions scenario RCP4.5 for 2081-2100 as a percentage of that model’s historical 1979-2005 simulations. The second set of maps shows similar comparisons but for the extreme emissions of RCP8.5. The modeled change of precipitation between the two periods varies substantially between models. Each model shows some areas getting wetter and other areas getting drier. The changes in RCP8.5 are just more extreme than RCP4.5. But the models disagree about which regions get wetter or drier. For example, the German model shows North Africa in 2081-2100 receiving only 40% of the rainfall of 1979-2005, whereas the Canadian and Japanese models predict North Africa will get up to 160% of the 1979-2005 rainfall. The Canadian model overestimated rainfall in North Africa by 80% and underestimated rainfall in Northern South America by about 60%.



The Flaw in Relying on Worst-Case-Scenario Climate Model

Dr. Ross McKitrick published an article in The Financial Post on June 23, 2020. He wrote: The purpose of global climate policy is to get us from the dangerous upper end of the forecast range down to the safe bottom end — we are already there. Whenever you read a media story about how we’re heading toward catastrophe if we continue operating “business as usual” — i.e., if we don’t slash carbon emissions — the reports are almost always referring to a model simulation using RCP8.5. And you can bet that nowhere in the story will they explain that RCP8.5 is an implausible worst-case scenario that was never meant to represent a likely base case outcome, or that scientists have begun castigating its usage as a prediction of a doomed business-as-usual future.



Testing the Tropical 200-300 mbar Warming Rate in Climate Models

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The tropical warming rate in climate models in the 200-300 mbar (9 to 12 km altitude) is compared to weather balloon measurement at a fundamental test of the models. Dr. McKirtick and Dr. Christy show that the average trend of the measurements is only about half of the climate models. They report a discrepancy across all runs of all models, taking the form of a warming bias at a sufficiently strong rate as to reject the hypothesis that the models are realistic. This means that the water vapour feedback is too strong in the models, and that they overestimate the warming due to greenhouse gas emissions.



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