60 Papers: Low Sensitivity

60 Papers Find Extremely Low CO2 Climate Sensitivity

(a) Quantified Low Climate Sensitivity to Doubled CO2

Florides and Christodoulides, 2009 (2X CO2 = ~0.02°C)

A very recent development on the greenhouse phenomenon is a validated adiabatic model, based on laws of physics, forecasting a maximum temperature-increase of 0.01–0.03 °C for a value doubling the present concentration of atmospheric CO2Moreover, data from palaeoclimatology show that the CO2-content in the atmosphere is at a minimum in this geological aeon. Finally it is stressed that the understanding of the functioning of Earth’s complex climate system (especially for water, solar radiation and so forth) is still poor and, hence, scientific knowledge is not at a level to give definite and precise answers for the causes of global warming.

Newell and Dopplick, 1979 (2X CO2 = ~.0.25°C )

Estimates of the atmospheric temperature changes due to a doubling of CO2 concentration have be with a standard radiative flux model. They yield temperature changes of >0.25 K.  It appears that the much larger changes predicted by other models arise from additional water vapor evaporated into the atmosphere and not from the CO2 itself. … It is important to stress…that CO2 is not the main constituent involved in infrared transfer. Water vapor plays the major role and ozone is also of importance.  With the infrared region divided into 22 spectral intervals, the infrared and solar fluxes have been computed at levels from the surface up to 5 mb using a procedure originally developed by Rodgers (1967) and modified by Dopplick (1972).  The procedure has previously been applied to the computation of heating rates for increased CO2 concentrations (Newell and Dopplick, 1970; Newell et al., 1972).  Table 1 gives the results of computations using standard climatological data for January. Twenty of the spectral intervals are dominated by water vapor and the other two contain CO2 (~15 µm) and O3 (~9.6 µm), although overlap with water vapor is also included. Calculations were performed for CO2 concentrations of 330 and 600 ppmv, taking care to include the changed CO2 concentrations also in the near-infrared solar absorption (cf. Newell et al., 1972). Both sets of computations were also repeated with cloud absent.   The infrared flux dominated by CO2, as is well known, is only about 10% of that controlled by water vapor. The decrease in infrared flux from the surface to the atmosphere due to the increase in CO2 ranges from 1.0 – 1.6 W m-2. The increased CO2 yields additional absorption of solar infrared radiation and therefore a decrease of solar energy available at the surface which ranges up to ~0.3 W m-2. The net change at the surface is an increase of 0.8 – 1.5 W m-2 with the smallest values at low latitudes.  … The fact that water vapor dominates CO2 in the radiation budget has been known and discussed for many years (see, e.g., Kondratiev and Niilisk, 1960; Möller, 1963; Zdunkowski et al., 1975) but it seems important to reemphasize when so much attention is being paid to CO2.
The conclusion is that at low latitudes the influence of doubling CO2 on surface temperatures is less than 0.25 K

Idso, 1998 (2X CO2 = ~0.4°C)

Over the course of the past 2 decades, I have analyzed a number of natural phenomena that reveal how Earth’s near-surface air temperature responds to surface radiative perturbations. These studies all suggest that a 300 to 600 ppm doubling of the atmosphere’s CO2 concentration could raise the planet’s mean surface air temperature by only about 0.4°C. Even this modicum of warming may never be realized, however, for it could be negated by a number of planetary cooling forces that are intensified by warmer temperatures and by the strengthening of biological processes that are enhanced by the same rise in atmospheric CO2 concentration that drives the warming.

Chylek et al., 2007 (2X CO2 = 0.39°C)

Consequently, both increasing atmospheric concentration of greenhouse gases and decreasing loading of atmospheric aerosols are major contributors to the top-of atmosphere radiative forcing. We find that the climate sensitivity is reduced by at least a factor of 2 when direct and indirect effects of decreasing aerosols are included, compared to the case where the radiative forcing is ascribed only to increases in atmospheric concentrations of carbon dioxide. We find the empirical climate sensitivity to be between 0.29 and 0.48 K/Wm-2 when aerosol direct and indirect radiative forcing is included.

Gates et al., 1981 (2X CO2 = 0.3°C)

Preliminary analysis of experiments on the climatic effects of increased CO2 with an atmospheric general circulation model and a climatological ocean
Preliminary results from numerical experiments designed to show the seasonal and geographical distribution of the climatic changes resulting from increased atmospheric CO2 concentration are presented. These simulations were made for both doubled and quadrupled CO2 levels with an improved version of the two-level OSU atmospheric GCM. In these experiments and in a control run with normal CO2, the solar radiation incident at the top of the model atmosphere and the sea-surface temperature and sea ice were given prescribed seasonal climatological variations. In January the globally averaged tropospheric temperature is increased with respect to the control mean by 0.30°C (0.48°C) for doubled (quadrupled) CO2, which may be compared with an interannual January temperature variability of 0.15°C in the control (as measured by the root-mean-square of January monthly averages in a 3-year control integration)

Gray, 2009 (2X CO2 = ~0.4°C)

CO2 increases without positive water vapor feedback could only have been responsible for about  0.1 – 0.2 °C of the 0.6-0.7°C global mean surface temperature warming that has been observed since the early 20th  century.  Assuming a doubling of CO2 by the late 21st  century (assuming no  positive water vapor feedback), we should likely expect to see no more than about 0.3-0.5°C global surface warming and certainly not the 2-5°C warming that has been projected by the GCMs [global circulation models].

Harde, 2014 (2X CO2 = 0.6°C)

The short- and long-wave absorption of the most important greenhouse gases water vapour, carbon dioxide, methane and ozone are derived from line-by-line calculations based on the HITRAN08-databasis and are integrated in the model. Simulations including an increased solar activity over the last century give a CO2 initiated warming of 0.2°C and a solar influence of 0.54°C over this period, corresponding to a CO2 climate sensitivity of 0.6 °C (doubling of CO2) and a solar sensitivity of 0.5°C (0.1 % increase of the solar constant).

Ollila, 2012 (2X CO2 = 0.51 °C)

Scientists are still debating the reasons for “global warming”. The author questions the validity of the calculations for the models published by the Intergovernmental Panel on Climate Change (IPCC) and especially the future scenarios. Through spectral calculations, the author finds that water vapour accounts for approximately 87% of the greenhouse (GH) effect and only 10% of CO2. A doubling of the present level of CO2 would increase the global temperature by only 0.51 °C without water feedback.

Zdunkowski et al., 1975., 1975 (2X CO2 = 0.5°C)

It is found that doubling the carbon dioxide concentration increases the temperature near the ground by approximately one-half of one degree [0.5°C] if clouds are absent. A sevenfold [700%] increase of the present normal carbon dioxide concentration increases the temperature near the ground by approximately one degree. Temperature profiles resulting from presently observed carbon dioxide concentration and convective cloudiness of 50% or less are compared with those resulting from doubled carbon dioxide concentrations and the same amounts of cloud cover. Again, it is found that a doubling [100% increase] of carbon dioxide increases the temperature in the lower boundary layer by about one-half of one degree.

Idso, 1980 (2X CO2 = ≤ 0.26°C )

The mean global increase in thermal radiation received at the surface of the earth as a consequence of a doubling of the atmospheric carbon dioxide content is calculated to be 2.28 watts per square meter. Multiplying this forcing function by the atmosphere’s surface air temperature response function, which has recently been determined by three independent experimental analyses to have a mean global value of 0.113 K per watt per square meter, yields a value of ≤ 0.26 K for the resultant change in the mean global surface air temperature. This result is about one order of magnitude less than those obtained from most theoretical numerical models, but it is virtually identical to the result of a fourth experimental approach to the problem described by Newell and Dopplick. There thus appears to be a major discrepancy between current theory and experiment relative to the effects of carbon dioxide on climate. Until this discrepancy is resolved, we should not be too quick to limit our options in the selection of future energy alternatives.

Schuurmans, 1983 (2XCO2 = ~0.3°C )

For detection purposes we need to know the so-called transient response of climate to a given increase of the atmospheric CO2 concentration (observed or predicted). Transient response patterns, however, are generally much less well known than equilibrium responses.  The problems encountered in specifying the transient CO2-induced climate signal are discussed in detail by Michael et al. in his book.  From his review we may conclude that there is some general agreement amongst different modellers that the transient response of global mean temperature to increased CO2 concentration of the atmosphere at present amounts to less than 0.5 K (estimates of [temperature response] now varying between 0.2 and 0.4 K).

Weare and Snell, 1974 (2X CO2 = 0.7°C )

Introduction: There has been in recent years a growing concern over possible inadvertent climate alteration by man’s activity (SMI, 1971; Matthews et al., 1971). As a result, there has been considerable effort devoted to developing predictive global climatic models (Budyko, 1969, 1972; Sellers, 1969, 1973), or to otherwise assessing the climatic effect of atmospheric pollutants (see, e.g., Manabe, 1971; Lamb, 1970; Rasool and Schneider, 1971; Bryson, 1972; Mitchell, 1970). This effort has been useful in providing tentative predictions and has certainly stimulated more interest and even controversy. However, the climatic models have relied heavily on simplified empirical parameterizations and, in general, none of the assessments have been very inclusive of many of the earth-atmosphere dynamic feedback mechanisms. For instance, one of the most important factors potentially affecting the radiation balance of the earth-atmosphere system is clouds because of their high reflectivity in the visible spectrum and absorption-emission in the infrared.
In Fig. 6 we present the results of altering atmospheric aerosol from the assumed present day-day value of about 0.1 optical depth units. … A doubling produces a 1K decrease in mean annual global surface temperature, whereas a fourfold increase produces somewhat more than a 3K decrease. … As may be seen in Fig. 7, a doubling of CO2 increase the mean annual global surface temperature according to our dynamical model by about 0.7K, but a sixfold increase only increases the temperature 1.7K. The nonlinearity is due to saturation of the 15 µm band.

Lindzen and Choi, 2011 (2X CO2 = 0.7°C)

As a result, the climate sensitivity for a doubling of CO2 is estimated to be 0.7K (with the confidence interval 0.5K – 1.3K at 99% levels). This observational result shows that model sensitivities indicated by the IPCC AR4 are likely greater than the possibilities estimated from the observations.

Kimoto, 2015  [full] (2X CO2= ~0.16°C)

The central dogma is critically evaluated in the anthropogenic global warming (AGW) theory of the IPCC, claiming the Planck response is 1.2K when CO2 is doubled. The first basis of it is one dimensional model studies with the fixed lapse rate assumption of 6.5K/km. It is failed from the lack of the parameter sensitivity analysis of the lapse rate for CO2 doubling. The second basis is the Planck response calculation by Cess in 1976 having a mathematical error. Therefore, the AGW theory is collapsed along with the canonical climate sensitivity of 3K utilizing the radiative forcing of 3.7W/m2 for CO2 doubling. The surface climate sensitivity is 0.14 – 0.17 K in this study with the surface radiative forcing of 1.1 W/m2

Ollila, 2014 (2X CO2 = ~ 0.27°C)

The Potency of Carbon Dioxide as a Greenhouse Gas     
According to this study the commonly applied radiative forcing (RF) value of 3.7 Wm-2 for CO2 concentration of 560 ppm includes water feedback. The same value without water feedback is 2.16 Wm-2 which is 41.6 % smaller. Spectral analyses show that the contribution of CO2 in the greenhouse (GH) phenomenon is about 11 % and water’s strength in the present climate in comparison to CO2 is 15.2. The author has analyzed the value of the climate sensitivity (CS) and the climate sensitivity parameter (l)using three different calculation bases. These methods include energy balance calculations, infrared radiation absorption in the atmosphere, and the changes in outgoing longwave radiation at the top of the atmosphere. According to the analyzed results, the equilibrium CS (ECS) is at maximum 0.6 °C and the best estimate of l is 0.268 K/(Wm-2 ) without any feedback mechanisms.

Harde, 2016 (2X CO2 = 0.7°C)

Including solar and cloud effects as well as all relevant feedback processes our simulations give an equilibrium climate sensitivity of CS = 0.7 °C (temperature increase at doubled CO2) and a solar sensitivity of SS = 0.17 °C (at 0.1 % increase of the total solar irradiance). Then CO2 contributes 40 % and the Sun 60 % to global warming over the last century.

Bates, 2016  (2X CO2 = ~1°C)

Estimates of 2xCO2 equilibrium climate sensitivity (EqCS) derive from running global climate models (GCMs) to equilibrium. Estimates of effective climate sensitivity (EfCS) are the corresponding quantities obtained using transient GCM output or observations. The EfCS approach uses an accompanying energy balance model (EBM), the zero-dimensional model (ZDM) being standard. GCM values of EqCS and EfCS vary widely [IPCC range: (1.5, 4.5)°C] and have failed to converge over the past 35 years. Recently, attempts have been made to refine the EfCS approach by using two-zone (tropical/extratropical) EBMs. When applied using satellite radiation data, these give low and tightly-constrained EfCS values, in the neighbourhood of 1°C. … The central conclusion of this study is that to disregard the low values of effective climate sensitivity (≈1°C) given by observations on the grounds that they do not agree with the larger values of equilibrium, or effective, climate sensitivity given by GCMs, while the GCMs themselves do not properly represent the observed value of the tropical radiative response coefficient, is a standpoint that needs to be reconsidered.

Evans, 2016 (2X CO2 = <0.5°C)

The conventional basic climate model applies “basic physics” to climate, estimating sensitivity to CO2. However, it has two serious architectural errors. It only allows feedbacks in response to surface warming, so it omits the driver-specific feedbacks. It treats extra-absorbed sunlight, which heats the surface and increases outgoing long-wave radiation (OLR), the same as extra CO2, which reduces OLR from carbon dioxide in the upper atmosphere but does not increase the total OLR. The rerouting feedback is proposed. An increasing CO2 concentration warms the upper troposphere, heating the water vapor emissions layer and some cloud tops, which emit more OLR and descend to lower and warmer altitudes. This feedback resolves the nonobservation of the “hotspot.” An alternative model is developed, whose architecture fixes the errors. By summing the (surface) warmings due to climate drivers, rather than their forcings, it allows driver-specific forcings and allows a separate CO2 response (the conventional model applies the same response, the solar response, to all forcings). It also applies a radiation balance, estimating OLR from properties of the emission layers. Fitting the climate data to the alternative model, we find that the equilibrium climate sensitivity is most likely less than 0.5°C, increasing CO2 most likely caused less than 20% of the global warming from the 1970s, and the CO2 response is less than one-third as strong as the solar response. The conventional model overestimates the potency of CO2 because it applies the strong solar response instead of the weak CO2response to the CO2 forcing.

Gervais, 2016 [full]  (2X CO2  = <0.6°C)

Conclusion: Dangerous anthropogenic warming is questioned (i) upon recognition of the large amplitude of the natural 60–year cyclic component and (ii) upon revision downwards of the transient climate response consistent with latest tendencies shown in Fig. 1, here found to be at most 0.6 °C once the natural component has been removed, consistent with latest infrared studies (Harde, 2014). Anthropogenic warming well below the potentially dangerous range were reported in older and recent studies (Idso, 1998; Miskolczi, 2007; Paltridge et al., 2009; Gerlich and Tscheuschner, 2009; Lindzen and Choi, 2009, 2011; Spencer and Braswell, 2010; Clark, 2010; Kramm and Dlugi, 2011; Lewis and Curry, 2014; Skeie et al., 2014; Lewis, 2015; Volokin and ReLlez, 2015). On inspection of a risk of anthropogenic warming thus toned down, a change of paradigm which highlights a benefit for mankind related to the increase of plant feeding and crops yields by enhanced CO2 photosynthesis is suggested.

Soon, Connolly, and Connolly, 2015 [full] (2X [400 ppm] CO2 = 0.44°C)

Nonetheless, let us ignore the negative relationship with greenhouse gas (GHG) radiative forcing, and assume the carbon dioxide (CO2) relationship is valid. If atmospheric carbon dioxide concentrations have risen by ~110 ppmv since 1881 (i.e., 290→400 ppmv), this would imply that carbon dioxide (CO2) is responsible for a warming of at most 0.0011 × 110 = 0.12°C over the 1881-2014 period, where 0.0011 is the slope of the line in Figure 29(a). We can use this relationship to calculate the so-called “climate sensitivity” to carbon dioxide, i.e., the temperature response to a doubling of atmospheric carbon dioxide. According to this model, if atmospheric carbon dioxide concentrations were to increase by ~400 ppmv, this would contribute to at most 0.0011 × 400 = 0.44°C warming. That is, the climate sensitivity to atmospheric carbon dioxide is at most 0.44°C.

Reinhart, 2017 (2X [400 ppm] CO2 = 0.24°C)

Our results permit to conclude that CO2 is a very weak greenhouse gas and cannot be accepted as the main driver of climate change. … The assumption of a constant temperature and black body radiation definitely violates reality and even the principles of thermodynamics. … [W]e conclude that the temperature increases predicted by the IPCC AR5 lack robust scientific justification. … A doubling [to 800 ppm] of the present level of CO2 [400 ppm] results in  [temperature change] < 0.24 K. … [T]he scientific community must look for causes of climate change that can be solidly based on physics and chemistry. … The observed temperature increase since pre-industrial times is close to an order of magnitude higher than that attributable to CO2.

Balling Jr, 1994  (2XCO2 = <1.0°C)

Close examination of the global temperature record, together with other factors, does not support the global warming models’ predictions – the thermal response to a doubling of CO2 is likely to be ‘remarkably small’
An additional problem of linking the observed changes in surface temperature to the build-up of greenhouse gases involves the timing of the warming.  The problem here is simple.  The amount of warming from 1893 to 1992 shown in Figure 1 is well-established at 0.45°C.  However, the amount of warming in the first half of the record (from 1893 to 1942) is 0.32°C; this result clearly shows that nearly three-quarters of the linear warming of this century had occurred before the time of the most rapid build-up of greenhouse gases.
As we have seen, the surface air temperature records show a linear increase of 0.45°C pver the past 100 years.  However, urban heat islands may cause a 0.05°C reduction, overgrazing and desertification may lower the trend by the same amount as the urban heat island effect, and stratospheric aerosol variations may lower the trend by 0.15°C.  And if we include the statistical association between sunspot cycle length and global temperature, the trend is almost eliminated. Even without considering the possible role of solar output, at least half of the warming of the past century can be explained by non-greenhouse phenomena, and most of that warming occurred in the first part of the record.
[T]he temperature record of the past century suggests that a doubling of carbon dioxide will produce a global temperature response at the lowest end of the model predictions – probably not more than 1.0°C.

Bellamy, 2007  (2XCO2= <1.0°C)

This paper demonstrates that the widely prophesied doubling of atmospheric carbon dioxide levels from natural, pre-industrial values will enhance the so-called ‘greenhouse effect’ but will amount to less than 1°C of global warming. It also points out that such a scenario is unlikely to arise given our limited reserves of fossil fuels—certainly not before the end of this century.

(b) Non-Quantified ‘Practically No Effect’, ‘Close To Zero’ CO2 Climate Sensitivity

Chillingar, 2009

Conventional theory of global warming states that heating of atmosphere occurs as a result of accumulation of CO2 and CH4 in atmosphere. The writers show that rising concentration of CO2should result in the cooling of climate. The methane accumulation has no essential effect on the Earth’s climate. Even significant releases of the anthropogenic carbon dioxide into the atmosphere do not change average parameters of the Earth’s heat regime and the atmospheric greenhouse effect. Moreover, CO2 concentration increase in the atmosphere results in rising agricultural productivity and improves the conditions for reforestation. Thus, accumulation of small additional amounts of carbon dioxide and methane in the atmosphere as a result of anthropogenic activities has practically no effect on the Earth’s climate.

Miskolczi, 2010

There are accumulating evidences that the greenhouse effect in the Earth’s atmosphere is not a ‘free’ parameter and anthropogenic global warming (AGW) estimates based on the classic greenhouse theory and CO2 doubling experiments (usually conducted by general circulation models) are totally wrong. Based on large number of observed atmospheric thermal and humidity structures and global scale simulations of the true greenhouse gas absorption properties of the atmosphere it is shown that the global average clear sky greenhouse effect is constant. The observed true infrared optical thickness of the clear atmosphere is 1.87 and this value proved to be very stable in the last 61 years. With the help of the observed relationships among the radiative flux components and the association of those relationships with known fundamental physical laws new structural equations of the global radiation field were established. The theoretically predicted IR optical thickness is fully consistent with, and supporting the observed value of 1.87.

Möller, 1963

The numerical value of a temperature change under the influence of a CO2 change as calculated by Plass is valid only for a dry atmosphere. Overlapping of the absorption bands of CO2 and H2O in the range around 15 μ essentially diminishes the temperature changes. New calculations give ΔT [temperature] = + 1.5° when the CO2 content increases from 300 to 600 ppm. Cloudiness diminishes the radiation effects but not the temperature changes because under cloudy skies larger temperature changes are needed in order to compensate for an equal change in the downward long-wave radiation. The increase in the water vapor content of the atmosphere with rising temperature causes a self-amplification effect which results in almost arbitrary temperature changes, e.g. for constant relative humidity ΔT = +10° in the above mentioned case. It is shown, however, that the changed radiation conditions are not necessarily compensated for by a temperature change. The effect of an increase in CO2 from 300 to 330 ppm can be compensated for completely by a change in the water vapor content of 3 per cent or by a change in the cloudiness of 1 per cent of its value without the occurrence of temperature changes at all. Thus the theory that climatic variations are affected by variations in the CO2 content becomes very questionable.       

Singer, 2006

Consistency or lack thereof between observed temperature trends and those predicted by Global Circulation Models (GCMs) are a contentious though important issue. The lack of consistency between observed and modeled temperature trends has frequently been used to argue against a significant human contribution to global warming – and vice versa. We present here additional and independent evidence that there is no agreement between observed and modeled warming trends in the tropical troposphere during the last two decades of the 20th century. This finding is shown to put constraints on surface trend and Climate Sensitivity, limiting them to values close to zero.

Willett, 1974

W.J. Humphreys, (1940, pp. 585-6), and outstanding meteorological physicist, after careful consideration of CO2 absorption and the water vapor absorption spectrum, concludes that either doubling or halving the present amount of carbon dioxide could alter but little the total amount of radiation actually absorbed by the atmosphere, and, therefore, seemingly, could not appreciably change the average temperature of the earth, or be at all effective in the production of marked climatic changes.”
In view of the mere 7% observed increase of CO2, of the conclusion of Humphreys quoted above and of the work of the numerous authorities quoted by him, the author is convinced that recent increases of atmospheric carbon dioxide have contributed much less than 5% of the recent changes of atmospheric temperature, and will contribute no more than that in the foreseeable future. Furthermore, the carbon dioxide hypothesis for the upward trend of northern hemispheric temperature from 1920-50 does not at all account for the fact that this trend terminated in higher middle latitudes before it even started in subtropical latitudes, where it peaked long after it terminated in high latitudes.

Sagan and Mullen, 1972

[W]e find a serious discrepancy between theory and observation. … A decline in the global temperature of Earth is likely to increase rather than decrease the albedo, but in any case the albedo decline required to explain the discrepancy appears to be out of the question.  Indeed, detailed global climate models suggest that a relative increase in [albedo] of only 2 percent is enough to induce extensive glaciation on Earth, which implies that the present climate is extremely sensitive to albedo.  This leaves changes in atmospheric composition as a possible explanation [for climate changes]. Major variations in the CO2 abundance will have only minor greenhouse effects because the strongest bands are nearly saturated.  A change the present CO2 abundance by a factor of 2 will produce directly a 2° variation in surface temperature. The CO2 abundance is highly controlled by silicate-carbonate equilibria; by buffering with seawater, which contains about 100 times the atmospheric CO2; and by the respiration and photosynthesis feedback loop.  The negative exponential dependence of the vapor pressure of water on reciprocal temperature implies that for a lower global temperature there is no likelihood of gaining more water vapor than the contemporary global average, about 1 g cm-2.   The only surviving alternative appears to be that the atmosphere of Earth 1 or 2 aeons ago contained some constituent or constituents, not now present, with significant absorption in the middle infrared, in the vicinity of the Wien peak of Earth’s thermal emission.

Oliver, 1976

A period of several decades existed (~1915-1945) in which volcanic activity was unusually light and, as mentioned earlier, the temperatures were higher than the preceding [1880s to 1910s] or, in fact, the subsequent (current) [1960s-1970s] period. … Numerous possible causes of climate change have been discussed in the literature, including both anthropogenic and natural factors. Two principal anthropogenic sources are often considered: changes in atmospheric carbon dioxide and changes in tropospheric dust. … The possible effects due to changes in CO2 are perhaps most readily subject to analysis, for good data do exist on atmospheric CO2 and its increase over recent decades. Thus, according to Reitan (1971), based on calculations by Manabe and Wetherald (1967), the increase in CO2 between the 1880’s and the 1960’s could have caused a mean temperature increase of 0.3°C. Unfortunately, however, such computations are based on assumptions of constant cloudiness, and possible changes in cloud cover are exceedingly important. Manabe and Wetherland (1967) show, for example, that a 1% increase in low cloudiness would cause an 0.8°C decrease in mean temperature; thus, a 0.3° warming could be compensated by a change of about 0.4% in low cloudiness. A change of 0.4% in low cloudiness would obviously be exceedingly difficult to detect. … Mitchell (1975) concluded that neither tropospheric particulates [anthropogenic pollution] nor atmospheric CO2, in concert or separately, could have accounted for the major part of the observed temperature changes of the past century.

Clark, 2010  (full paper)

Energy transfer at the Earth’s surface is examined from first principles. The effects on surface temperature of small changes in the solar constant caused by the sunspot cycle and small increases in downward long wave infrared (LWIR) flux due to a 100 ppm increase in atmospheric CO2 concentration are considered in detail. The changes in the solar constant are sufficient to change ocean temperatures and alter the Earth’s climate. The surface temperature changes produced by an increase in downward LWIR flux are too small to be measured and cannot cause climate change. The assumptions underlying the use of radiative forcing in climate models are shown to be invalid. A null hypothesis for CO2 is proposed that it is impossible to show that changes in CO2 concentration have caused any climate change, at least since the current composition of the atmosphere was set by ocean photosynthesis about one billion years ago.
The ‘clear sky’ upper limit for the CO2 induced increase in evaporation is below the measurement uncertainty bounds. Long term averages of surface air temperatures are approximately 2 C below the corresponding ocean surface temperatures. This means that there is usually no direct heating of the ocean by the atmosphere, as required by the Second Law of Thermodynamics. As discussed below (Figure 15), any slight increase in atmospheric H2O vapor concentration will produce atmospheric cooling through increased upward LWIR emission under these conditions. Latent heat of evaporation is not released until the water condenses, which is generally at altitudes above 1 km. It is therefore impossible for an increase in downward atmospheric LWIR flux of 1.7 W.m−2 to heat the ocean.

Ramanathan et al., 1989

Water vapour and cloud are the dominant regulators of the radiative heating of the planet. ..The greenhouse effect of clouds may be larger than that resulting from a hundredfold increase in the CO2 concentration of the atmosphere. … The size of the observed net cloud forcing is about four times as large as the expected value of radiative forcing from a doubling of CO2. The shortwave and longwave components of cloud forcing are about ten times as large as those for a CO2 doubling.

Khilyuk and Chilingar, 2006  (full)

The current global warming is most likely a combined effect of increased solar and tectonic activities and cannot be attributed to the increased anthropogenic impact on the atmosphere. Humans may be responsible for less than 0.01°C (of approximately 0.56°C (1°F) total average atmospheric heating during the last century … [G]lobal natural forces are at least 4–5 orders of magnitude greater than available human controls.

Newell and Dopplick, 1970

The greenhouse theory as usually discussed puts such a “heating” interpretation on the CO2 changes even though the actual effect of a CO2 increase is to diminish the cooling rate. It is well to stress that the conditions here are such that all other items are unchanged. The term greenhouse is of dubious applicability because the greenhouse glass leads to higher temperatures by reducing turbulent eddy heat losses, rather than by a radiative influence (Kondratyev, 1965). To place the CO2 contribution to temperature change in perspective it is compared with other radiative components at two levels in Table 2. Clear skies are assumed. Carbon dioxide is secondary to water vapor in the troposphere as noted by others (e.g., Rodgers and Walshaw, 1966) and dominant in the lower stratosphere under the conditions assumed here. When looking for a potential influence of global pollution on the tropospheric temperature it would be therefore wise to pay careful attention to the water cycle and its possible modification, particularly as it enters also through the effect of latent heat.

Manabe and Möller, 1961

The heating due to the absorption of solar radiation by carbon dioxide is still small compared with the effects of other processes. However around the tropopause, where the contributions of various radiative processes are at a minimum, it is not always negligible.
 The long wave radiation by carbon dioxide has a strong tendency to destroy the existing latitudinal increase of the temperature. The net effect of these radiative processes could barely maintain the stratospheric temperature approximately constant with latitude and hardly explains the sharp latitudinal temperature increase observed in the stratosphere.

Libby, 1970

Item: American Scientist, January-February 1970, p. 18, “Though dire effects on climate of an increase in CO2 have been predicted, they are far from being established. The cycle is not really understood; carbon dioxide may well prove to be the least objectionable or the only beneficial addition to the atmosphere from industrial sources … Atmospheric CO2 is the source of almost all the carbon of organic compounds in our bodies. It is likely that CO2 from industrial sources has actually increased the productivity of terrestrial vegetation since 1900, and that as fossil fuels are exhausted and industry goes to atomic power there will be a decrease, possibly ten percent, in agricultural yields….”

Gervais, 2014

The anthropogenic CO2 additional warming extrapolated in 2100 is found lower than 0.1°C in the absence of feedbacks. The global temperature data are fitted with an oscillation of period 60 years added to a linear contribution. The data which support the 60-year cycle are summarized, in particular sea surface temperatures and sea level rise measured either by tide gauge or by satellite altimetry. The tiny anthropogenic warming appears consistent with the absence of any detectable change of slope of the 130-year-long linear contribution to the temperature data before and after the onset of large CO2 emissions.

Rasool and Schneider, 1971

It is found that, although the addition of carbon dioxide in the atmosphere does increase the surface temperature, the rate of temperature increase diminishes with increasing carbon dioxide in the atmosphere.  … It is found that even an increase by a factor of 8 in the amount of CO2, which is highly unlikely in the next several thousand years, will produce an increase in the surface temperature of less than 2°K.

Chilingar et al., 2014

Even significant releases of anthropogenic carbon dioxide and methane into the atmosphere do not change average parameters of the Earth’s heat regime and have no essential effect on the Earth’s climate. Thus, petroleum production and other anthropogenic activities resulting in accumulation of additional amounts of methane and carbon dioxide in the atmosphere have practically no effect on the Earth’s climate.

Ludwig et al., 1973

There have been a number of theoretical models developed in which the effect of the CO2 increase is linked with a mean global temperature increase. In general, these models have not been too successful because the end results were unreasonably sensitive to minor changes in some critical assumptions. For example, Manabe and Wetherald (ref. 7) calculate that the estimated increase in CO2 concentration by the year 2000 would raise the average atmospheric temperature by 0.5° C. Whether this temperature increase would really occur is open to question, since it could be counterbalanced by a 1% change in total average cloudiness (ref. 8). In addition, the apparent increase of global aerosol concentration (ref. 9) could have a similar counterbalancing effect.

Singer, 1976

The distribution of the radiating gases is largely responsible for the layering of the Earth’s atmosphere. The troposphere extends from sea level up to approximately 12 km at which point the temperature has dropped to approximately -60°C. Water vapor is about 10 times more important than carbon dioxide, both for radiative heating by absorbing solar radiation and for radiative cooling. In the stratosphere, however, radiative heating by the absorption of solar radiation by ozone is dominant.

Kauppinen et al., 2014

We will show that changes of relative humidity or low cloud cover explain the major changes in the global mean temperature. We will present the evidence of this argument using the observed relative humidity between years 1970 and 2011 and the observed low cloud cover between years 1983 and 2008. One percent increase in relative humidity or in low cloud cover decreases the temperature by 0.15 °C and 0.11 °C, respectively. In the time periods mentioned before the contribution of the CO2 increase was less than 10% to the total temperature change.

Lightfoot and Mamer, 2014

Each method shows that, on average, water vapour contributes approximately 96% of current greenhouse gas warming. Thus, the factors controlling the amount of water vapour in the air also control the earth’s temperature.   … TOTAL BACK RADIATION OF ALL GHG Figure 7 is FAQ 1.1 Figure 1 from page 96 of AR4. It shows the radiation balance for the earth and that the back radiation of all of the greenhouse gases is 324 W m-2. This is the value used to calculate the RF [radiative forcing] of CO2 at 378 ppmv as (8.67/324)/100 = 2.7% back radiation of the total of all of the greenhouse gases  … From Table 1, CO2 accounts for 2.7% of the global warming while all of the other gases account for approximately 0.7% for a total of approximately 3.4%. It becomes evident that, on average, water vapour accounts for approximately 96% of the current global [greenhouse effect] warming. This is an important finding because it leads to the conclusion that the factors controlling the average level of water vapour in the atmosphere also control atmospheric temperature. … [O]n average, each molecule of CO2 is surrounded by approximately 23 molecules of water vapour at ground level. …  If the warming effect of water molecules and CO2 molecules were the same, then the contribution of CO2 would be (1/22.7) = 4.4% of that of water vapour. But from the previous section, water molecules are 1.6 times more effective at warming than CO2 molecules. Using this value and the ratio of 22.7:1, the contribution of CO2 to warming of the atmosphere is approximately (1/22.7)/1.6 = 2.8% of that of water vapour. As water vapour is approximately 96% of the total RF of all of the GHG, the contribution of CO2 is approximately 4% less than this, i.e., 2.69%. If the average RH were 60%, the contribution of CO2 would be ((1/27.4)/1.32) x 0.96 = 2.65%. For practical purposes, these values are the same as the 2.7% obtained by the quadratic model.

Arrak, 2011

Arctic Warming is Not Greenhouse Warming
After two thousand years of slow cooling Arctic, warming suddenly began more than a century ago. It has continued, with a break in the middle, until this day. The rapid start of this warming rules out the greenhouse effect as its cause. Apparently the time scale of the accumulation of CO2 in the air and the Arctic warming does not match. It is likely that the cause of this warming was a relatively sudden rearrangement of the North Atlantic current system at the turn of the century that directed warm currents into the Arctic Ocean. All observations of Arctic warming can be accounted for as consequences of these flows of warm water to the Arctic. This explains why all attempts to model Arctic warming have failed: Models set up for greenhouse warming are the wrong models for non-greenhouse warming. It turns out that satellites which have been measuring global temperature for the last 31 years cannot see any sign of current warming that supposedly started in the late seventies. This absence of warming in the satellite record is in accord with the observations of Ferenc Miskolczi on IR absorption by the atmosphere. What warming satellites do see is only a short spurt that began with the super El Nino of 1998, raised global temperature by a third of a degree in four years, and then stopped. It was of oceanic origin.

Kahl et al., 1993

Absence of evidence of greenhouse warming over the Arctic Ocean in the past 40 years
In particular, we do not observe the large surface warming trends predicted by models; indeed, we detect significant surface cooling trends over the western Arctic Ocean during winter and autumn. This discrepancy suggests that present climate models do not adequately incorporate the physical processes that affect the polar regions. … The lack of widespread significant warming trends leads us to conclude that there is no strong evidence to support model simulations of greenhouse warming over the Arctic Ocean for the period 1950-1990.  Our results, combined with the inconsistent performance of model simulations of Arctic climate indicate a need to understand better the physical processes that affect polar regions, especially atmosphere-ice-ocean interactions, ocean heat transfer and cloud radiative effects

Robock, 1979

Carbon dioxide produced by fossil fuel burning does not seem to have had a significant effect on climatic change as yet. With it the results are slightly better for the entire record and slightly worse for the most recent portion. This conclusion should be qualified because there may be compensating anthropogenic influences such as aerosols, and the model tends to underemphasize the CO2 effect as compared to more sophisticated radiation models which treat the stratosphere explicitly

Fang et al., 2011

In recent decades, there have been a number of debates on climate warming and its driving forces. Based on an extensive literature review, we suggest that (1) climate warming occurs with great uncertainty in the magnitude of the temperature increase; (2) both human activities and natural forces contribute to climate change, but their relative contributions are difficult to quantify; and (3) the dominant role of the increase in the atmospheric concentration of greenhouse gases (including CO2) in the global warming claimed by the Intergovernmental Panel on Climate Change (IPCC) is questioned by the scientific communities because of large uncertainties in the mechanisms of natural factors and anthropogenic activities and in the sources of the increased atmospheric CO2 concentration. More efforts should be made in order to clarify these uncertainties.

Hertzberg et al., 2017 

This study examines the concept of ‘greenhouse gases’ and various definitions of the phenomenon known as the ‘Atmospheric Radiative Greenhouse Effect’. The six most quoted descriptions are as follows: (a) radiation trapped between the Earth’s surface and its atmosphere; (b) the insulating blanket of the atmosphere that keeps the Earth warm; (c) back radiation from the atmosphere to the Earth’s surface; (d) Infra Red absorbing gases that hinder radiative cooling and keep the surface warmer than it would otherwise be – known as ‘otherwise radiation’; (e) differences between actual surface temperatures of the Earth (as also observed on Venus) and those based on calculations; (f) any gas that absorbs infrared radiation emitted from the Earth’s surface towards free space. It is shown that none of the above descriptions can withstand the rigours of scientific scrutiny when the fundamental laws of physics and thermodynamics are applied to them.

Sawyer, 1972

The output of human industry is still very much less than the total mass of the atmosphere and man-made energy is still small compared with the energy of meteorological systems. The total industrial output of heat each day is, for example, considerably less than 0.1% of the total kinetic energy of the atmosphere, which itself is destroyed by friction and replaced naturally within a few days. Another useful comparison is that of the total man-made heat output in Britain with natural processes over the same area.  Even over this area of relatively intense human activity man’s efforts are relatively quite small – man-made heat is less than 1% of the energy received from the Sun. It also must be remembered that the mass of the atmosphere is enormous compared with the products of human activity. The total mass of the atmosphere is more than 500 times the mass of the known coal reserves, for example, and human activities will not change its chief constituents
Even global mean temperatures have varied by 0.6°C from a minimum around 1880 to the last maximum around 1940. Against this background a change of  0.6°C by the end of the century [2000] will be not be easy to distinguish from natural fluctuations and certainly is not a cause for alarm. Even a doubling of the amount of carbon dioxide in the atmosphere, which would probably require the burning of a large part of the known fuel reserves, would appear to result in a rise of temperature little above that experienced in the climatic optimum which followed the last ice age.  

Gerlich and Tscheuschner, 2009

Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics
It is an interesting point that the thermal conductivity of CO2 is only one half of that of nitrogen or oxygen. In a 100 percent CO2 atmosphere a conventional light bulb shines brighter than in a nitrogen-oxygen atmosphere due to the lowered thermal conductivity of its environment. But this has nothing to do with the supposed CO2 greenhouse effect which refers to trace gas concentrations. Global climatologists claim that the Earth’s natural greenhouse effect keeps the Earth 33°C warmer than it would be without the trace gases in the atmosphere. About 80 percent of this warming is attributed to water vapor and 20 percent to the 0.03 volume percent CO2. If such an extreme effect existed, it would show up even in a laboratory experiment involving concentrated CO2 as a thermal conductivity anomaly. It would manifest itself as a new kind of ‘superinsulation’ violating the conventional heat conduction equation. However, for CO2 such anomalous heat transport properties never have been observed.

Miskolczi, 2014

This paper presents observed atmospheric thermal and humidity structures and global scale simulations of the infrared absorption properties of the Earth’s atmosphere. These data show that the global average clear sky greenhouse effect has remained unchanged with time. A theoretically predicted infrared optical thickness is fully consistent with, and supports the observed value. It also facilitates the theoretical determination of the planetary radiative equilibrium cloud cover, cloud altitude and Bond albedo. In steady state, the planetary surface (as seen from space) shows no greenhouse effect: the all-sky surface upward radiation is equal to the available solar radiation. The all-sky climatological greenhouse effect (the difference of the all-sky surface upward flux and absorbed solar flux) at this surface is equal to the reflected solar radiation. The planetary radiative balance is maintained by the equilibrium cloud cover which is equal to the theoretical equilibrium clear sky transfer function. The Wien temperature of the allsky emission spectrum is locked closely to the thermodynamic triple point of the water assuring the maximum radiation entropy. The stability and natural fluctuations of the global average surface temperature of the heterogeneous system are ultimately determined by the phase changes of water. Many authors have proposed a greenhouse effect due to anthropogenic carbon dioxide emissions. The present analysis shows that such an effect is impossible.

Ollila, 2013

Analyses of IPCC’s Warming Calculation Results
Some researchers have noticed that the warming calculations of Intergovernmental Panel on Climate Change (IPCC) are not always based on the atmospheres, which use the global average values. CO2 effect of 26% in greenhouse phenomenon is based on the modified U.S. Standard Atmosphere 1976 (USST 76 atmosphere) containing only 50% of water in comparison to the true value. The calculations prove that the warming of 0.76°C can be achieved if the USST 76 atmospheric model is applied and constant relative humidity (RH) assumed. The analysis also reveals that IPCC’s scenario presentation contains choices, which make the warming results look higher than they should be. All the climate sensitivity values above 1.7 °C conflict with the explanation given by IPCC for the 1750 – 2005 periods. The global warming potential (GWP) values of CH4 and N2O are applicable only for small concentration changes and in higher concentrations these greenhouse (GH) gases are even weaker than CO2. The ultimate worst case scenario is the release of methane from the methane clathrates on the ocean floor. The calculations show that the release would cause 2.1°C temperature increase, which is only 68% of the CO2 warming effect. The spectral analysis show that in the prevailing atmospheric conditions the warming potency of methane is about 14% from the potency of CO2, and the same of N2O is about 17%. The effect of water in the same conditions is 15.2 times greater than that of CO2.

Dyson, 1977

The magnitude of this negative feed-back effect of atmospheric CO2 upon itself depends on many ecological interactions which have yet to be disentangled. The effect could be negligibly small, or it could be as large as 3 x 109 tons of carbon per yr. In summary, there is insufficient evidence to decide whether the carbon content of the biosphere has decreased, increased or remained stationary in response to the manifold human activities of recent decades. There exists a huge literature attempting to assess or to prognosticate the effects of the increasing atmospheric CO2 on the climate of the earth. Such attempts are useful and necessary, hut they run into formidable technical difficulties. Even the mean global temperature rise caused by a given quantity of CO2 is subject to great uncertainty: and the effects of CO2 on local and time-variable phenomena (which may be crucially important to agriculture and other human activities) are more uncertain still. It is possible that the rise in CO2 will be on balance beneficial to mankind, especially in reducing climatic extremes in very cold and very dry regions.

Hertzberg and Schreuder, 2016

The authors evaluate the United Nations Intergovernmental Panel on Climate Change (IPCC) “consensus” that the increase of carbon dioxide in the earth’s atmosphere is of anthropogenic origin and is causing dangerous global warming, climate change and climate disruption. They conclude that the data do not support that supposition. Most of the currently accepted scientific interpretations are examined and the given impression that increased atmospheric carbon dioxide will increase the earth’s surface and/or air temperature is questioned. New insight is offered drawing a conclusion that no additional warming is possible due to the increase of atmospheric carbon dioxide. Acceptance of that IPCC paradigm is incurring costly and draconian efforts to reduce CO2 emissions, tax such emissions and replace fossil fuel combustion by alternative energy systems whether such alternatives will achieve the desired results or not. The totality of the data available on which that theory is based is evaluated here, from Vostok ice core measurements, to residence time of CO2 in the atmosphere, to more recent studies of temperature changes that inevitably precede CO2 changes, to global temperature trends, to the current ratio of carbon isotopes in the atmosphere, to satellite data for the geographic distribution of atmospheric CO2, to the effect of solar activity on cosmic rays and cloud cover. Nothing in the data supports the supposition that atmospheric CO2 is a driver of weather or climate, or that human emissions control atmospheric CO2. Furthermore, CO2 is not a pollutant, but an essential ingredient of the Earth’s ecosystem on which almost all life depends via photosynthesis. This paper rejects the new paradigm of “climate science” and asserts that the traditional, century old meteorological concepts for the factors that control weather and climate remain sound but need to be reassessed.

Avakyan, 2013

The author associates the recently observed climate warming and carbon dioxide concentration growth in the lower atmospheric layers with variations of solar-geomagnetic activity in global cloud formation and the significant decrease in the role of forests in carbon dioxide accumulation in the process of photosynthesis. The contribution of the greenhouse effect of carbon-containing gases to global warming turns out to be insignificant.

Zhao, 2011

Although there is little controversy about global warming, there is still a debate regarding whether global warming is mainly due to anthropogenic greenhouse gas emissions. Many researchers strongly believe that global warming is mainly due to greenhouse gas emissions. However, other scientists argue that the standard models overstate the importance of CO2 emissions. We propose a reduced-form regression-based test. With the temperature and CO2 emissions data from the U.S., we find little evidence in support of the notion that recent global warming is mainly due to CO2 emissions. Our results, therefore, call for more research on the causes of recent global warming.

(c) Rising CO2 Causes Surface Cooling

Choudhury and Kukla, 1979

Impact of CO2 on cooling of snow and water surfaces
The levels of CO2 in the atmosphere are being increased by the burning of fossil fuels and reduction of biomass. It has been calculated that the increase in CO2 levels should lead to global warming because of increased absorption by the atmosphere of terrestrial longwave radiation in the far IR (>5 μm). From model computations, CO2 is expected to produce the largest climatic effect in high latitudes by reducing the size of ice and snow fields. We present here computations of spectral radiative transfer and scattering within a snow pack and water. The results suggest that CO2 significantly reduces the shortwave energy absorbed by the surface of snow and water. The energy deficit, when not compensated by downward atmospheric radiation, may delay the recrystallisation of snow and dissipation of pack-ice and result in a cooling rather than a warming effect.

Idso, 1984

An analysis of northern, low and southern latitude temperature trends of the past century, along with available atmospheric CO2 concentration and industrial carbon production data, suggests that the true climatic effect of increasing the CO2 content of the atmosphere may be to cool the Earth and not warm it, contrary to most past analyses of this phenomenon. A physical mechanism is thus proposed to explain how CO2 may act as an inverse greenhouse gas in Earth’s atmosphere. However, a negative feedback mechanism related to a lowering of the planet’s mean surface albedo, due to the migration of more mesic-adapted vegetation onto arid and semi-arid lands as a result of the increased water use efficiency which most plants experience under high levels of atmospheric CO2, acts to counter this inverse greenhouse effect. Quantitative estimates of the magnitudes of both phenomena are made, and it is shown that they are probably compensatory. This finding suggests that we will not suffer any great climatic catastrophe but will instead reap great agricultural benefits from the rapid increase in atmospheric CO2 which we are currently experiencing and which is projected to continue for perhaps another century or two into the future.

Ellsaesser, 1984  (full)

If additional greenhouse gases are added to the atmosphere, it is logical to expect that the greenhouse blanket will thicken; i.e., the average altitude from which the atmosphere emits energy to space will rise above its present level of 6 km. But, since the absorbed solar energy which has to be rejected remains essentially unchanged, the radiating temperature also must remain the same.  That is, the average atmospheric temperature at the new higher level of the top of the greenhouse blanket must warm to the temperature existing now at the present top of the greenhouse blanket.  And if the lapse rate remains the same, then the temperature of the Earth’s surface will also warm. This is a somewhat simplistic but physically valid picture of the mechanism by which increases in the greenhouse gas content of the atmosphere will lead to climatic warming. Unfortunately, this simple picture of how the greenhouse effect operates is of little help in quantifying the amount of warming to be expected.  To see why this is so, examine Fig. 3 [p. 7].  This shows a terrestrial IR spectrum taken by Nimbus IV near Guam on 27 April 1970 on a background of temperature-labeled black body curves and with the wave length range of the principal atmospheric IR absorbers (emitters) indicated.  It is obvious that water, including the dimer, (H2O)2 – believed to be responsible for the continuum absorption (and emission) of water vapor, is the principal emitter, without even considering the effect of clouds, which are also composed of water.  And since this spectrum is taken at latitude 15.1°N, it appears quite credible that the global average temperature of this emitter is 255 K. On the other hand, the IR flux from the CO2 band centered near 15-microns, is both a small fraction of the total and is coming from an emitter with a temperature near 220 K (-50 to -55°C). Returning to Fig. 2, this temperature range is found in the altitude range 12 to 20 km.  If the top of this CO2 greenhouse blanket were to be raised by the addition of CO2 and maintained at constant temperature, this would have little or no effect on the temperature at the surface and, if anything, might cause the surface to cool (i.e., if this radiating layer were pushed above 20 km without changing its temperature).

Bryson and Dittberner, 1976

A simple mean hemispheric temperature model has been constructed in the form of a differential equation which is a function of three independent variables: carbon dioxide content of the air, volcanic ejecta and anthropogenic particulate pollution. This model appears to simulate the behavior of Northern Hemisphere mean temperatures as well as they are known and gives a different pattern of behavior for the Southern Hemisphere. By more completely accounting for those anthropogenic processes which produce both lower tropospheric aerosols and carbon dioxide, such as fossil fuel burning and agricultural burning, we calculate an expected slight decrease in surface temperature with an increase in CO2 content. Though an invariant “solar constant” was assumed, an unmistakable 20–25 year periodicity was found in the difference between the calculated and observed direct solar flux reaching the earth’s surface, suggesting a definite but small periodic variation in the solar constant.

Schmithüsen et al., 2015

Abstract: For this region [central Antarctica], the emission to space is higher than the surface emission; and the greenhouse effect of CO2 is around zero or even negative, which has not been discussed so far. We investigated this in detail and show that for central Antarctica an increase in CO2 concentration leads to an increased long-wave energy loss to space, which cools the Earth-atmosphere system.
For most of the Antarctic Plateau, GHE-TES [greenhouse effect as measured by the Tropospheric Emission Spectrometer] is close to zero or even slightly negative; i.e., the presence of CO2 increases radiative cooling. Over Greenland, the greenhouse effect of CO2 is also comparatively weak but invariably positive. An evaluation of monthly averages of GHE-TES shows that the increased cooling due to CO2 of Antarctica is strongest during austral spring and autumn. … Central Antarctica is the only place on the planet where increased CO2 concentrations lead to an increased LW energy loss to space [cooling]. In the Northern Hemisphere the lowest, but invariably positive, [CO2] forcing values are seen over Greenland and Eastern Siberia.