Stefani on the Sun vs. CO2 as climate drivers

By Andy May


Frank Stefani, of the Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics, has published a very interesting new paper that compares the solar “aa” index and CO2 emissions to global SST (sea surface temperatures using the HadSST4.2 dataset) and finds a CO2 sensitivity (TCR or the “Transient Climate Response”) of 1.1 to 1.4K. This is at the low end of the IPCC TCR range of 1.2 to 2.4K (IPCC, 2021, p. 93), but quite close to the values calculated by Lewis and Curry and Nicola Scafetta (Lewis & Curry, 2018), (Scafetta, 2023), and (Lewis, 2023). Scafetta found a plausible range of TCR (versus HadSST4.2) of 1.0K to 1.2K and Lewis & Curry report a range of 0.9K to 1.7K for TCR versus HadCRUT4. The estimates are compared in Table 1.

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Is the Ocean Surface a boundary condition?

By Andy May

My previous post was a discussion about an important paper by Elizabeth Wong and Peter Minnett. The paper discusses the interaction between the thermal (or electromagnetic) skin layer (TSL) on the ocean and the bulk ocean. The TSL is only about 10 microns thick on average, although the thickness and temperature profile through it and under it changes throughout the day and night. Virtually all greenhouse gas (GHG) infrared radiation (IR) is absorbed in the TSL, whereas over 99% of solar shortwave radiation (SW) passes right through it and is absorbed deeper in the ocean (the “bulk ocean”) in the tropics under clear skies (Wong & Minnett, 2018).

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Efficacy of downwelling IR

By Andy May

Solar radiation penetrates oceans to depths of 10-100 meters (depending on wavelength and water clarity), directly heating the ocean mixed layer. Greenhouse gas (GHG) infrared (IR), being longwave, is absorbed in the top ~10 microns (the thermal or electromagnetic skin layer or “TSL”), where it influences temperature gradients, evaporation, and conduction. The TSL lies on top of the mixed layer and has a different temperature. Below the TSL, especially in the daytime or in the presence of very light winds, there can develop a temperature gradient between it and the “foundation” temperature or the mixed layer temperature (see figure 1). The vertically nearly constant mixed layer temperature is maintained by turbulence and convection and follows overlying air temperature trends (although not the actual air temperature) by a few days to a few weeks, or even longer, depending upon the season and latitude. Higher latitudes respond slower and lower latitudes quicker; wind speed has a large effect on the lag.

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The Neoglacial Period

By Andy May

Most agree that the Milankovitch cycles of eccentricity, obliquity, and precession drive long-term global and hemispheric climate changes, see figure 4 in this post for a brief description of them. The modern climate debate is about short-term climate change. The “consensus” says that human emissions have caused “the most rapid change” or “temperatures are the warmest in X years” (Lecavalier et al., 2017) and (IPCC, 2021, p. 8) with X varying from one thousand years to over 100,000 years. Obviously, we only have global instrumental data for the past 170 years or so, so any global or hemispheric data before then is either local or proxy temperature data.

The mainstream view is to ignore inconvenient data that shows CO2 and methane air concentrations do not correlate with temperature during the Holocene Epoch, or the past 12,000 years as shown in figure 4 here. Correlation is not causation, but the lack of correlation normally precludes causation. If changes in heat storage in the climate system are ignored, as is often done, then only outside forcing can cause climate change. Since recent climate changes (since 1950) have been too rapid to be caused by the Milankovitch orbital cycles, the only outside forces left are the Sun and greenhouse gases (GHGs). Since the oceans and atmosphere change the amount of heat they store, as opposed to emit to space, climate changes as climatic heat storage changes (Irvine, 2014). We can observe this in the 60-70-year climate or ocean oscillations, like the Atlantic Multidecadal Oscillation (AMO, see here and here).

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Holocene Glacier Records

By Andy May

Glacier length changes through time, they advance when the local climate around them is colder and retreat when it is warmer (Bray, 1968). Over century and greater time scales glacier length is considered a highly reliable indicator of both regional and worldwide warming trends according to Olga Solomina, Johannes Oerlemans, and the IPCC (Solomina et al., 2008), (Oerlemans, 2005) & (IPCC, 2001, pp. 127-130). While studying glacier lengths can illuminate long-term warming or cooling trends in glaciated areas is true, the idea that they can reveal hemisphere-wide or global climatic trends is somewhat speculative.

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Holocene Warming

By Andy May

I find it amazing that some papers still state:

“air temperatures in the [Arctic or globally] are now at their warmest in the past 6,800–7,800 y, and that the recent rate of temperature change is unprecedented over the entire Holocene.” (Lecavalier et al., 2017)

While it is remotely possible that current Arctic or global average temperature is higher than any seen in the past 6,800 years, it is very unlikely and can’t be demonstrated with data we have today. It is almost certainly true that the rate of change in global or Arctic temperature observed recently is not unprecedented in the Holocene Epoch. This modern myth has been thoroughly debunked in the literature and seeing it pop up in PNAS and elsewhere is disconcerting. I thought peer-review was supposed to catch such errors.

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Re-evaluating the Concern of Climate Change

By Andy May

I’ve just been made aware of a paper critical of the “consensus” view that man-made climate change is dangerous. It is by Ashutosh Sharma, Vinit Vithalrai Shenvi, and Mohit Sain of the MS Ramaiah Institute of Technology in India (or MSRIT) (Sharma et al., 2024). It was published just two months before “Carbon Dioxide and a Warming Climate are not problems,” by Marcel Crok and myself (May & Crok, 2024) and makes similar points, at least until we reach the paper’s conclusions. The paper argues that: “climate change policies impose unwarranted economic strains on nations and impede technological advancement.”

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The Cost of Wind and Solar Power Backup

By Andy May

There have been many attempts to compare wind and solar power generation to generation with natural gas and other fossil fuels. I have summarized and criticized these attempts before, see here and here. Another excellent discussion of the topic is in this TPPF report by Michael Reed and Brent Bennet. Reed and Bennett estimate that modifying the Texas grid to handle wind and solar output variability cost Texas electricity consumers $2.3 billion in 2023. The purpose of this post is not to cover the whole issue, as Reed and Bennett do, but only discuss how to account for the natural gas swing generation used to backup wind and solar when these sources are unavailable, like on windless nights. The power one can produce using wind turbines and solar panels varies a lot from place to place and from time to time. Figure 1 shows the mix in Texas on 27 January 2026 at 12:21PM.

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Weather Reanalysis Models

By Andy May

My new paper (May, 2025) emphasizes that while many of the underlying observations used to build weather reanalysis datasets, such as ERA5 (European Centre for Medium-Range Weather Forecasts or ECMWF Reanalysis v5) (Soci et al., 2024) or MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, Version 2) (Gelaro et al., 2017), are from radiosondes, weather reanalysis models are still models and have the same problems that other models have. Thus, they are not observations or measurements, like those in radiosonde data repositories such as IGRA2, and should not be treated as such. The reanalysis models assimilate surface measurements and satellite data in addition to radiosonde data and blend the measurements together into a global or regional grid using a general circulation atmospheric model. Weather reanalysis models produce reasonably consistent, physics-based periodic (usually every 6 to 12 hours) estimates of the global atmospheric state (Bloom et al., 1996), but they are not observations. Dr. Hans Hersbach of ECMWF (European Centre for Medium-Range Weather Forecasts) provides us with figure 1 below which is an illustration of the data assimilation process in ERA5.

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The Monthly ITCZ Central Latitude

By Andy May

The Intertropical Convergence Zone or ITCZ is where the trade winds from the Northern and Southern Hemisphere converge and where the column-integrated meridional (north-south) circulation and the “near-surface meridional mass flux” vanishes according to Adam et al., 2016. For a history of the discovery of the ITCZ see Nicholson, 2018. The ITCZ is not the solar equator, the latitude where the Sun is directly overhead at noon, but it is closely related to it, and they move in a coordinated fashion. The ITCZ is an oceanic phenomenon and doesn’t really exist over land in the same way as described here, except in coastal areas (Nicholson, 2018).

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