If the observations of the AMOC are wrong and the multi-model mean of the CMIP6 ensemble
members does represent the twentieth century AMOC, the only problem with the models is
that there is a large range of trends in the CMIP6 ensembles.

From NoTricksZone

By Kenneth Richard on 9. November 2023

IPCC models rooted in assumptions that we humans can and do control the Atlantic Ocean’s circulation with our daily-activity CO2 emissions have been wrong since the mid-1980s. Why should we still believe in them?

The latest IPCC report continues to say it is “very likely” the Atlantic Meridional Ocean Circulation (AMOC), a fundamental climate parameter, will weaken (and unleash cooling, catastrophic storms, drought, floods) in the 21st century.

But, as the authors of a new study note, since the mid-1980s the 84 (CMIP5) and 56 (CMIP6) AMOC models have been contradicted by observations in both magnitude and sign. The AMOC has not been declining in response to increases in atmospheric CO2. There is even evidence of trend increases.

“[W]e find that neither the CMIP5 nor the CMIP6 ensemble mean are successful at representing the observational AMOC data. … We show that both the magnitude of the trend in the AMOC over different time periods and often even the sign of the trend differs between observations and climate model ensemble mean, with the magnitude of the trend difference becoming even greater when looking at the CMIP6 ensemble compared to CMIP5.”

So, as the scientists ask, why should we trust future modeled predictions?

“[I]f these models cannot reproduce past variations, why should we be so confident about their ability to predict the future?”

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