Tag: warming effect

The Effect of a Colder Solid’s Thermal Radiation on a Warmer Solid Exposed to Sunlight

It is experimentally shown that the thermal radiation from a transparent, colder solid has the capacity to influence a solid warmer than it to become even warmer, under the right circumstances. This dispels the critique of the greenhouse effect that, as heat only flows from hot to cold, the effect is thermodynamically impossible. Even so, significant portions of the theory of the greenhouse effect remain experimentally unproven, signaling caution rather than uncritical acceptance of the theory.

From Watts Up With That?

experiments performed July 10th 2024

by Dale Cloudman

Abstract

It is experimentally shown that the thermal radiation from a transparent, colder solid has the capacity to influence a solid warmer than it to become even warmer, under the right circumstances. This dispels the critique of the greenhouse effect that, as heat only flows from hot to cold, the effect is thermodynamically impossible. Even so, significant portions of the theory of the greenhouse effect remain experimentally unproven, signaling caution rather than uncritical acceptance of the theory.

Introduction

A long-running debate about the physical reality of the greenhouse effect centers around whether the thermal radiation from the colder atmosphere can possibly have a warming effect on the warmer Earth’s surface. The argument goes as follows: as heat only flows from hot to cold, the radiation emitted by a colder object cannot possibly cause a warmer object to become warmer. It might have a reduced cooling effect, but under no circumstances can it result in a warming effect.

The most salient features of such debates are that neither side provides experimental evidence in their defense, and that the debates frequently devolve into heated arguments, which is generally an indicator that solid arguments are lacking. As genuine scientific knowledge is acquired via experimentation performed in physical reality, and not theory or “experiments” (sic!) consisting of computer simulations, I sought to settle the debate once and for all with a properly-performed experiment.

I constructed a de Saussure-style hotbox, above which I placed a clear glass plate separated by a good amount of space. I pointed it towards the Sun, and, left to its own devices, the bottom of the box got to around 100ºC, with the glass plate getting to around 30ºC. I then swapped the glass plate with an identical one that was pre-heated to 60-70ºC, and the result was unmistakable: the already much hotter bottom of the box got even hotter as a result. I ruled out any possible conductive or convective effects, concluding it was due to increased thermal radiation coming from the +30-40ºC warmer glass plate. Although this neatly dispels this particular critique of the greenhouse effect, significant obstacles remain before being able to accept that the greenhouse effect behaves as-described.

The Demonstration

The apparatus (Figure 1, Figure 2) consists of a hotbox made of styrofoam, with the inside floor being cardboard and the inside walls and floors spray-painted black. Two layers of thin plastic polyethylene film suppress convection with the outside air. Surrounding these is another piece of styrofoam to further prevent heat loss through the sides. Cotton padding between the styrofoam pieces provides further insulation.

On top of the hotbox are two styrofoam walls that support an extra-clear glass plate on top. This is the glass that is swapped with an identical, hotter version during the experiment. A middle mount point allows the optional mounting of another plate in the middle.

Temperatures are measured with Type K thermocouples, labeled and color-coded for ease of reference. Styrofoam pieces immediately above yet not touching them serve as radiation shields. The solar insolation is measured with an Apogee SP-510-SS pyranometer, and the net infrared gain or loss is measured with an Apogee SL-510-SS pyrgeometer.

I pointed the apparatus at the sun and let it heat up on its own. In the meantime, I set aside an identical extra-clear glass plate, on top of which I placed an aluminum plate with a pot of water on top. An immersion heater kept the water temperature at a constant 80-90ºC, which heat diffused downwards to heat the glass plate.

Once the bottom plate exceeded 100ºC, I swapped the cool glass with the hot glass, first by hovering the hot glass above it, then removing the cool glass and placing the hot glass in the same position. This swapping technique provides a dip in measured solar insolation due to both glasses absorbing the sunlight rather than just one. This clearly delineates the swaps, and ensures there is no extra heating effect due to slightly higher insolation that would happen if we first removed one glass and then replaced it with the other glass.

I performed five swaps as above, with Tcoolglass measuring 30-38ºC and Thotglass measuring between 67-75ºC at the start of the swaps. The result was clear and unambiguous in every case: Tbottom shot up rapidly in response. The following two runs are representative (Figure 3):

As is evident, before the first swap on the graph, Tbottom was increasing at a certain steady pace. After the swap to the hot glass (delineated by the purple vertical line), the rate of increase rapidly shot up. Once swapped back to the cool glass (delineated by the gray vertical line), Tbottom stabilized around 108ºC. It remained there for ~5 minutes, after which another swap caused it to increase rapidly again.

It is notable that at the exact moment of the swaps, the net infrared radiation Net IR picked up by the pyrgeometer remains negative yet increases. That is, the bottom’s radiative cooling is measurably lessened as a result of this swap.

To rule out differences between the two glass plates, such as the possibility of slightly more solar insolation which could cause a temperature change, I did two swaps with both glass plates at around the same temperature. With these swaps, no difference was observed in the evolution of Tbottom or in the Net IR.

Confirming the Radiative Nature of the Effect

It is important to rule out any convective effects as having caused the increase. The hotter glass will, of course, heat the air around it as well. How do we know that Tbottom didn’t get hotter because the hotter glass heated the air in-between, which then heated the thin plastic films, which then reduced the convective loss of the bottom and caused its temperature to increase?

The evidence is three-fold. First, we can observe that Tlowair did not noticeably increase as a result of the swap. Indeed, it was warmer before the swap than after (Figure 4):

Second, by including Tthin1 and Tthin2 in the graph, we can see that Tbottom increased first, and only nearly half a minute later did Tthin1 start to increase, soon after which Tthin2 increased as well (Figure 5). Thus the temperature increase started from bottom to top, not from top to bottom, meaning the observed increase could not be due to the air being heated from the top. 

Third, I repeated the experiments, but with a thin borosilicate plate mounted in the middle of the apparatus (Figure 6). Borosilicate is highly absorbent of infrared radiation. If the effect is radiative, we would expect the borosilicate to absorb any extra thermal radiation from the hotter glass, preventing Tbottom from increasing. This is precisely what happened. During these runs, the Net IR did not change when the hotter glass was swapped in, nor did Tbottom respond to the swaps.

Thus we have to conclude that the increased thermal radiation from the hotter glass is what caused the bottom to increase in temperature, even though the hotter glass itself was much cooler than the bottom.

Analysis

How does this not violate the laws of thermodynamics, wherein heat only flows from hot to cold? The answer is that one must consider all the heat flows in the system. When Tbottom is at a steady temperature around 108ºC, it is because the amount of heat it is gaining from all sources is equal to the amount of heat it is losing to all sinks. At that temperature, the only heat it is gaining is from the sunlight, which is actually the thermal radiation emanating from our nearby star with its surface temperature of 5900K. It is at the same time losing heat conductively with the bottom of the hotbox and the walls, convectively with the air in the box, and radiatively with the plastic wrap layers, the glass, and the sky above. The hotbox itself is also losing heat convectively with the outside air.

When the hotter glass is swapped in, effectively the only change is that now the bottom is losing less heat radiatively to the glass. With all else being equal, it is thus now gaining more heat from the sunlight than it is losing to all other sources, and the result is an increase in temperature. Notably, without the much hotter sun as a heat source, the increase in temperature would not be observed; only a reduced cooling effect would occur.

Conclusion

There are several key differences between the experiment performed here and the theorized radiative greenhouse effect, such that this experiment does not serve as verification of the latter.

  1. The hotbox is heavily insulated and enclosed to suppress convective heat loss. By contrast, the majority of the heat loss by the Earth’s surface is due to convective loss to the air.
  2. The temperature ranges are different, with the Earth’s surface being around 15ºC and the air ranging from 15ºC to -55ºC with increasing altitude, contrasted with 100ºC for the black bottom and 30-70ºC for the glass.
  3. The colder object is a solid plate of glass as opposed to a column of atmospheric air, i.e. a large volume of gas.
  4. The warmer object is a uniform pitch-black plate, as distinct from the Earth’s surface with its varied terrain, soil, plant, foliage, ice, snow, water, etc. 
  5. The greenhouse effect is due to the air becoming more absorbent of and emissive of thermal radiation at the same temperature, while the experimental result was due to the colder object retaining the same emissive properties yet becoming hotter.
  6. The observed time duration was minimal and no conclusions can be drawn about the total magnitude of the effect or what effects it may have in the long run.

    Indeed, the greenhouse effect theory has a large gap when it comes to the empirical demonstration of the greenhouse effect’s total effect on surface temperatures. It largely relies on a simplified calculation that shows the Earth’s average temperature would be -18ºC without any atmosphere. This calculation even includes the albedo effect of clouds, which would not be present without an atmosphere. Further it ignores all the distinctions listed above, and doesn’t account for the adiabatic lapse rate, which is the main reason why the bottom of the grand canyon is +50ºC warmer on average than the peak of Mount Everest. Such a lapse rate occurs entirely due to non-radiative effects, and therefore would have some effect even if the air were fully transparent to infrared radiation.
  7. The observed temperature increase here was due to swapping in a hotter glass plate that was externally heated by another heat source (i.e. neither the sun nor the black bottom). This is in contrast with the greenhouse effect, where the atmosphere’s thermal radiation that is theorized to result in a much warmer surface temperature, is initially warmed by the surface itself. This gives the appearance that it presents a situation where an object is able to heat itself up with its own heat – first the atmosphere at the same temperature emits thermal radiation according to its own temperature, which then results in a warmer surface, that then in turn heats the atmosphere further, etc., in a (diminishing) feedback loop.

    Although the experiment performed here indicates that the presence of the sun ought to make this possible, and Infrared Halogens appear to exploit an analogous mechanism to reduce energy consumption, an experiment should be done to confirm this is the case. It is notable that past experiments have failed to definitively show a powerful effect: R W Wood’s 1909 experiment showed “scarcely a difference of one degree” between two hotboxes, one with a radiatively-absorbent glass lid and one with a radiatively-transparent rock salt lid, where we would expect the radiatively-absorbent lid to result in a much hotter temperature due its higher radiative emissions as well. More recently, a re-do of Wood’s experiment “performed more carefully” by Pratt actually replicated the result, despite being heavily critical of Wood: a difference of 1.1ºC between the floor of a hotbox with a glass lid vs one with a rock salt lid. Pratt further showed that the glass lid was actually 6.2ºC hotter than the rock salt lid. This further complicates the analysis as convective heat transfer is proportional to temperature difference and indicates the +1.1ºC result is at least in part due to reduction of convective heat loss.
  8. Finally, even if the basic greenhouse effect were to be conclusively demonstrated, it is well-known that the current levels of CO2 are already saturated with regards to higher concentrations causing higher thermal emissions. The enhanced greenhouse effect is said to occur due to the much colder higher-altitude layers of the atmosphere absorbing and emitting more thermal radiation, thus having a cascading effect on the air immediately below it, which in turn has an effect on the air below, and so on up to the surface. In other words, the hotter absorbing element in the enhanced greenhouse effect is also atmospheric air, and not a solid object. This provides further complications as atmospheric air can freely travel vertically up and down, and hot air tends to expand and rise.

In conclusion, although the thermodynamic possibility of colder objects causing warmer objects to increase in temperature has finally been conclusively demonstrated, a lack of experimental verification of other facets of the greenhouse effect theory warrants caution before accepting its conclusions.

Climate Model Bias 3: Solar Input

In part 2 we discussed the IPCC hypothesis of climate change that assumes humans and our greenhouse gas emissions and land use choices are the climate change “control knob.” This hypothesis underpins their attempts to model Earth’s climate. But the model output fails to match many critical observations and in some cases the model/observation mismatches are getting worse with time.

From Watts Up With That?

By Andy May

In part 2 we discussed the IPCC hypothesis of climate change that assumes humans and our greenhouse gas emissions and land use choices are the climate change “control knob.”[1] This hypothesis underpins their attempts to model Earth’s climate. But the model output fails to match many critical observations and in some cases the model/observation mismatches are getting worse with time.[2] Since these mismatches have persisted through six major iterations of the models, it is reasonable to assume the flaw is in the assumptions, that is within the hypothesis itself, as opposed to being in the model construction. In other words, it is likely the IPCC conceptual model should be scrapped, and a new one using different assumptions constructed. In this post we examine their underlying assumption that the Sun has not varied significantly, at least from a climate perspective, over the past 150-170 years.

As well-explained by Bob Irvine,[3] there are only two things that contribute to the thermal energy content of a planet, the amount of incoming energy and the energy residence time within the system. These two things, along with the climate system heat capacity, determine the surface temperature. Arrhenius assumed and the IPCC still assumes the Sun delivers a nearly constant amount of energy to Earth over periods of a few hundred years, constant enough that it has no impact on our climate. In addition, they work with annual averages to avoid seasonal and orbital changes. In AR6, the base period is 1750 to 2019. The IPCC assumes the Sun is invariant, at least on an annual basis, over this period and volcanic activity is just slightly negative, as shown in figure 2.[4] AR6 summarizes their views as follows:

“Changes in solar and volcanic activity are assessed to have together contributed a small change of –0.02 [–0.06 to +0.02] °C since 1750 (medium confidence).”AR6 p. 962.

The change of “-0.02°C” is indistinguishable from zero. Since the IPCC assumes that solar input to Earth’s climate system does not change, temperature only varies as a function of the “energy residence time,” which they assume is controlled by human activity and greenhouse gas emissions.

As explained in part 2, greenhouse gases absorb radiation emitted by Earth’s surface and use it to warm the lower atmosphere, thus delaying its eventual escape to space. It is uncontroversial that adding more of these gases increases the delay, warming the planet’s surface.

The IPCC assumes that the radiative forcing for a doubling of CO2 from 1750 levels is 3.9[5] W/m2 or less and that the climate impact of this forcing change is roughly equivalent to a change in solar forcing of 3.9 W/m2.[6] But a 3.9 W/m2 change in greenhouse gas emissions from the atmosphere in the infrared frequencies cannot penetrate the top millimeter of the ocean. Thus, it has a different impact than a 3.9 W/m2 change in solar radiation, part of which penetrates more than 100 meters into the ocean before it is fully absorbed. Oceans cover 70% of Earth’s surface and have a low albedo (reflectivity) to sunlight, thus the oceans absorb most sunlight reaching Earth.

Figure 2. The IPCC AR6 model simulated temperature change components for the period 1750-2019. Source: AR6, p 961, figure 7.7.

Downwelling greenhouse gas radiation warms the surface of the ocean briefly, then most of it is quickly carried away by the overlying wind or as latent heat of evaporation. It has a short residence time in the ocean and in Earth’s climate system. A change in incoming solar radiation is absorbed deeper in the ocean and has a longer residence time. This increases the ocean warming effect at the point of incidence and spreads the new thermal energy over a larger volume of water. The difference in the surface warming effect can be a factor of three or more, Watt-per-Watt, relative to a change in greenhouse gas back-radiation.[7]

Evidence that Bob Irvine’s hypothesis is correct includes the change in ocean temperatures over the course of one approximately 11-year solar cycle.[8] The shallow ocean heat storage above the 22°C isotherm,[9] increases almost an order of magnitude more than the direct effect[10] of the solar cycle radiation increase. Further, this change is in phase with the solar cycle. Small changes in the Sun’s output can accumulate over time, increasing their effect on total climate system heat storage.

Wigley and Raper calculated that for a change in solar output of about 1.1 W/m2, roughly the change over one solar cycle, the direct change in Earth’s surface temperature should theoretically be in the range of 0.014°C to 0.025°C, which is undetectable.[11] However Judith Lean shows the observed surface temperature change, due to the increase in solar activity is about 0.1°C, 4 to 7 times what is expected and the increase in the upper atmosphere is 0.3°C, more than an order of magnitude more than expected from the change in radiation delivered to Earth.[12]

Lean also adds that were the Sun to become anonymously low, like during the Maunder Solar Grand Minimum (from 1645 to 1715) the expected global surface temperature cooling would still be less than a few tenths of a °C. This is only true if the cooling is linear with the change in radiation and if there are no unexpected amplifiers in the climate system, both assumptions are unlikely. We know that there are amplifiers in the climate system because the warming and cooling over the solar cycle are more than the theoretical change as Wigley and Raper have shown. The warming and cooling could be linear with the change in radiation, but there is no reason to assume this, Earth’s surface is complex and ever changing.[13]

More simply put, we know that the climate system somehow amplifies changes in insolation, but we don’t know exactly how. We know that solar output in the Maunder Solar Grand Minimum was less than now and the change from current solar output is small in percentage terms, but we have no idea what the effect on Earth’s climate of the change was, only that historical records and climate proxies suggest the effect was very large.

Known solar cycles correlate well with known climate cycles and are in phase with them.[14] Various hypotheses have been proposed to show how the Sun’s output changes over time periods of a thousand years or less. These are periods short enough to affect surface temperature from 1750, near the end of the Little Ice Age,[15] to 2019. The problem is that although a correlation between solar activity proxies[16] and climate change can be demonstrated,[17] a mechanism for the change in solar activity cannot. Attempts to explain solar variability by internal changes in the Sun only work in some cases. For example, Frank Stefani and colleagues have shown how the approximately 193-year de Vries solar cycle may be a beat period between the 22.14 Hale Solar Cycle and the 19.86-year orbit of the Sun around the solar system barycenter.[18]

Nicola Scafetta and Antonio Bianchini have shown that the orbits of the planets around the Sun correlate with solar activity proxies.[19] However, exactly how the small gravitational changes influence the solar dynamo is unclear. Thus, the hypothesis that solar activity is regulated within the Sun itself cannot completely reproduce observations, and planetary tidal forces seem too weak to accomplish the changes. These gaps in our knowledge of the mechanisms impede the acceptance that multi-centennial or multi-millennial solar changes can influence our climate. The Sun does change according to accepted solar proxies, like carbon-14 and beryllium-10 records, but the change mechanism is unclear.

The problem with the IPCC (and Arrhenius’) assumptions is that they ignore this empirical and theoretical evidence that solar output and/or solar energy input to the Earth’s climate system varies significantly over periods of a few hundred years. Their obsession with human greenhouse gases has blinded them to possible natural influences on climate change that they should be investigating. This is not to say that human greenhouse gases have no effect, it is likely that they do have some effect, but evidence suggests that natural influences, like the Modern Solar Maximum[20] and ocean oscillations,[21] play a significant role also.

There is a large body of peer-reviewed papers on the subject of solar activity as a climate change driver, yet AR6 ignores most of them. A very comprehensive review of recent research on the effect of the Sun on Earth’s climate is presented in a recent paper by Ronan Connolly and 22 colleagues.[22] In the paper they cite 396 papers on the connection between the Sun and climate, as opposed to only 68 in AR6 WG1,[23] both AR6 WG1 and the paper by Connolly, et al. were first published in 2021. This illustrates how selective the IPCC authors were in what research was considered in their report.

There is no valid reason to assume that the Sun was constant in its effect on Earth’s climate from 1750 until today. The usual reasoning is that observed changes in solar output are too small, in terms of power delivered per square meter (W/m2) relative to changes caused by increasing greenhouse gases, but as Irving explains these two sources of change are not comparable because the frequency content of the two sources are different.

Summary

The goal of this post is not to convince anyone that solar variability is responsible for all or part of modern global warming, a subject that is well covered elsewhere.[24] The point is that the IPCC reports and the CMIP models do not consider or investigate this possibility.

It is true that exactly how solar variability occurs and how it affects climate are not known, but the Sun does vary, and the variations correlate with climate changes. It is unlikely that climate changes are a direct result of the change in insolation, the solar changes are amplified by Earth’s climate system somehow.

We also do not know how much solar output has varied since 1650, the middle of the devastatingly cold Little Ice Age and the onset of the Maunder Solar Grand Minimum. There are several possible reconstructions of solar output since then. Figure 3 shows one of them constructed from an ice core beryllium-10 isotope record by Steinhilber, et al. The major climatic periods since 0AD are noted on it, and the Solar Grand Minima are identified.

Figure 3. The Steinhilber, et al. (2009) TSI reconstruction from 10berylium isotopes. The solar grand minima are identified, as well as the major climatic periods since 0AD.

The absolute values of delta-TSI (the change in total solar irradiation), in W/m2, plotted in Figure 3 are based on one of many possible modern TSI reconstructions (PMOD) and may not be accurate, but their values relative to one another are reasonable. None of the modern satellite TSI reconstructions are well supported, and the debate over which one is the best is furious and ongoing. See the discussion here for an introduction to the debate. It is best to not consider the absolute value of the Y axis in Figure 3, and consider it a TSI index, no one really knows how much TSI has changed, even over the satellite era. Further, as we’ve seen, how TSI changes relate to climate changes quantitatively is also not known. All we know is that they generally change together.

In Figure 3 we can see that colder periods, like the Little Ice Age, have some solar peaks and some warmer periods, and the Medieval Warm Period has solar lows. None of the climatic periods identified in Figure 3 were uniformly cold or warm. What we call the Little Ice Age, had some hot periods, and the Medieval Warm Period had cold periods (see the section after figure 2 here for references). Further, the correlation between solar activity and climate is not exact, nor is it uniform and synchronous over the whole planet. This is probably because of the effects of convection and atmospheric and oceanic circulation that I examine in the next post. Climate change is complicated.

The beginning and end of the climate periods identified in figure 3 are approximate, and mostly a judgement call. All the climate periods start and end at different times in different places.

However, we do know that some solar proxy reconstructions correlate well with climate proxies since 1850 (see Table 1 here),[25] and that alone is justification for additional research. Solar variability can explain anywhere from zero to almost 100% of the warming since 1850, depending upon the datasets used.[26]

This is a very brief summary of the evidence that changes in solar activity affect climate. More comprehensive discussions of possible mechanisms and the evidence for them are available.[27] Suffice it to say that this is an area of research that is too often ignored and brushed away as unimportant, especially by the IPCC. The sometimes excellent correlations in the peer-reviewed literature between solar activity and climate change alone should be enough to spur research. The fact that the IPCC has ignored these correlations is evidence of bias.

A point we will make many times in this series is that the Earth is not a uniform single thermodynamic body. Its surface is constantly changing. Treating it as a simple thermodynamic body, and one that can be characterized by a global average temperature is a huge mistake. Next, in part 4, we will discuss the potential impact of long-term changes in convection patterns.

Download the bibliography here.



  1. (Lacis, Hansen, Russell, Oinas, & Jonas, 2013), (Lacis, Schmidt, Rind, & Ruedy, 2010), and (IPCC, 2021, p. 179) ↑


  2. (McKitrick & Christy, A Test of the Tropical 200- to 300-hPa Warming Rate in Climate Models, Earth and Space Science, 2018), (McKitrick & Christy, 2020), (Lewis, 2023), (IPCC, 2021, p. 990) ↑


  3. (Irvine, A Thought Experiment; Simplifying the Climate Riddle, 2023) and (Irvine, A comparison of the efficacy of green house gas forcing and solar forcing, 2014) ↑


  4. (IPCC, 2021, p. 961) ↑


  5. (IPCC, 2021, p. 925) ↑


  6. (IPCC, 2021, p. 959), (Hansen, et al., 2005), and (IPCC, 2013, pp. 664-667) ↑


  7. (Irvine, A Thought Experiment; Simplifying the Climate Riddle, 2023) and (Irvine, A comparison of the efficacy of green house gas forcing and solar forcing, 2014). Irvine provides estimates of the surface warming “efficacy” of greenhouse gas forcing versus solar forcing. ↑


  8. Also called the Schwabe solar cycle. ↑


  9. An isotherm is a plane of equal temperature, in this case 22° below the ocean surface. ↑


  10. (White, Dettinger, & Cayan, 2003). The change in radiation expected ocean temperature change is done with the Stefan-Boltzmann equation. The expected change in heat content assumes a solar cycle radiation change of about 0.1 W/m2. ↑


  11. (Wigley & Raper, 1990) ↑


  12. (Lean, 2017) ↑


  13. https://andymaypetrophysicist.com/2017/09/09/hadcru-power-and-temperature/ ↑


  14. (Connolly et al., 2021), (Soon W. , et al., 2023), (Scafetta N. , Empirical assessment of the role of the Sun in climate change using balanced multi-proxy solar records., 2023), and (Soon, Connolly, & Connolly, 2015). ↑


  15. (Behringer, 2010) and (May, Are fossil-fuel CO2 emissions good or bad?, 2022) ↑


  16. (Scafetta N. , Understanding the role of the sun in climate change, 2023c) and (Scafetta N. , Empirical assessment of the role of the Sun in climate change using balanced multi-proxy solar records., 2023) ↑


  17. (Connolly, et al., 2023), Table 1 ↑


  18. (Stefani, Horstmann, Klevs, Mamatsashvili, & Weier, 2023) ↑


  19. (Scafetta & Bianchini, Overview of the Spectral Coherence between Planetary Resonances and Solar and Climate Oscillations, 2023b) and (Scafetta & Bianchini, The Planetary Theory of Solar Activity Variability: A Review, 2022) ↑


  20. (Vinós & May, The Sun-Climate Effect: The Winter Gatekeeper Hypothesis (I). The search for a solar signal, 2022) and (Usoskin, Solanki, & Kovaltsov, 2007) ↑


  21. (Vinós & May, The Winter Gatekeeper hypothesis (VII). A summary and some questions, 2022f), (Wyatt & Peters, A secularly varying hemispheric climate-signal propagation previously detected in instrumental and proxy data not detected in CMIP3 data base, 2012b), (Wyatt, Kravtsov, & Tsonis, Atlantic Multidecadal Oscillation and Northern Hemisphere’s climate variability, 2012a), and (Wyatt & Curry, 2014). ↑


  22. (Connolly et al., 2021) ↑


  23. (Soon, Connolly, & Connolly, 2024, p. 60) ↑


  24. (Connolly et al., 2021), (Soon, Connolly, & Connolly, Re-evaluating the role of solar variability on Northern Hemisphere temperature trends since the 19th century, 2015), (Crok & May, 2023), (Hoyt & Schatten, 1997), and (Haigh, 2011) ↑


  25. (Connolly, et al., 2023), see Table 1. ↑


  26. (Connolly et al., 2021) ↑


  27. (Soon, Connolly, & Connolly, Re-evaluating the role of solar variability on Northern Hemisphere temperature trends since the 19th century, 2015), (Connolly et al., 2021), (Soon W. , et al., 2023), (Vinós, Climate of the Past, Present and Future, A Scientific Debate, 2nd Edition, 2022), (Hoyt & Schatten, 1997), and (Haigh, 2011). ↑