Consider the idea that incremental CO2 promotes reduced cloud cover, ending up warming the planet through increased ASR (absorbed solar radiation). Is it reasonable to think that the climate models could ever represent clouds and precipitation with sufficient fidelity to support this concept? Short answer – No.
About the uncertainty of measured precipitation data, I found a web page for NOAA’s “Global Precipitation Climatology Project (GPCP) Monthly Analysis Product” and generated this image for May 2025.
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I asked Grok, the X AI agent: “For the “Global Precipitation Climatology Project (GPCP) Monthly Analysis Product” generated by NOAA’s Physical Sciences Laboratory, please explain the meaning of the “Monthly Error Surface Precipitation” values in mm/day.”
An excerpt from the response:
“Example
If a grid cell in the GPCP Version 2.3 Monthly Analysis Product reports a precipitation rate of 3 mm/day with a monthly error of 0.5 mm/day for a given month, this indicates:
The best estimate of average daily precipitation for that month is 3 mm.
The true precipitation rate could reasonably range between 2.5 and 3.5 mm/day, based on the error estimate.
This uncertainty could affect applications like validating climate models or studying precipitation trends, so users should account for it in their analyses.”
I followed up: “Please compute the thermal flux uncertainty of a +/- 1 mm/day estimated error in the monthly precipitation value. Report the answer in units of +/- W/m^2.”
The response, summarized at the end:
“The thermal flux uncertainty corresponding to a ±1 mm/day error in the monthly precipitation value is approximately ±29 W/m².”
https://x.com/i/grok?conversation=1938952771492864329
Have ANY of the climate models ever had ANY diagnostic or prognostic authority concerning the overall response of clouds and precipitation to the minor longwave radiative effect of incremental CO2? No.
How can this be so confidently stated? Because the models must inherit the large uncertainty in the observed data, which is involved in tuning the simulation of precipitation, which necessarily involves the tuning of cloud parameters.
The implication is that no one knows – whether by models or not – that the computed radiative influence of incremental CO2 has anything to do with the reported trends of reduced cloud cover and increased ASR from the satellite data.
Thank you for listening.