From Dr. Roy Spencer:
If we assume ALL *observed* warming of the deep oceans and land since 1970 has been due to humans, we get an effective climate sensitivity to a doubling of atmospheric CO2 of around 1.9 deg. C. This is considerably lower than the official *theoretical* model-based IPCC range of 2.5 to 4.0 deg. C.
Via a Phys.org article:
Spencer and Christy’s climate model, based upon objective measured data, found carbon dioxide does not have as big of an effect of warming of the atmosphere when compared with other climate models.
“For over 30 years, dozens of highly sophisticated computerized climate models based upon theory have been unable to agree on an answer. That’s why we developed our own one-dimensional climate model to provide an answer,” says. Dr. Spencer.
When compared to other current climate models, the research results from Spencer and Christy’s one-dimensional climate model approached the bottom end of the range, 1.9° Celsius. The lower UAH value indicates that the climate impact of increasing carbon dioxide concentrations is much less that that based on other climate models.
The paper, published in Theoretical and Applied Climatology:
Effective climate sensitivity distributions from a 1D model of global ocean and land temperature trends, 1970–2021
Current theoretically based Earth system models (ESMs) produce Effective Climate Sensitivities (EffCS) that range over a factor of three, with 80% of those models producing stronger global warming trends for 1970–2021 than do observations. To make a more observationally based estimate of EffCS, a 1D time-dependent forcing-feedback model of temperature departures from energy equilibrium is used to match measured ranges of global-average surface and sub-surface land and ocean temperature trends during 1970–2021. In response to two different radiative forcing scenarios, a full range of three model free parameters are evaluated to produce fits to a range of observed surface temperature trends (± 2σ) from four different land datasets and three ocean datasets, as well as deep-ocean temperature trends and borehole-based trend retrievals over land. Land-derived EffCS are larger than over the ocean, and EffCS is lower using the newer Shared Socioeconomic Pathways (SSP245, 1.86 °C global EffCS, ± 34% range 1.48–2.15 °C) than the older Representative Concentration Pathway forcing (RCP6, 2.49 °C global average EffCS, ± 34% range 2.04–2.87 °C). The strongest dependence of the EffCS results is on the assumed radiative forcing dataset, underscoring the role of radiative forcing uncertainty in determining the sensitivity of the climate system to increasing greenhouse gas concentrations from observations alone. The results are consistent with previous observation-based studies that concluded EffCS during the observational period is on the low end of the range produced by current ESMs.
Full paper with open access is here:
For a description of climate sensitivity, see Everything Climate