This post lists 22 reasons as to why we should be skeptical of CAGW (catastrophic anthropogenic global warming) which claims human CO2-emissions are dangerously heating up the Earth’s atmosphere, requiring urgent mitigating measures to counteract. It’s my opinion that anthropogenic global warming is minuscule at only 0.0018°C per 1ppmv of CO2 and the punitive green-taxes, carbon offset programs and disruptive geoengineering projects are all unnecessary and a waste of time and resources.

1) CO2 has quite a trivial warming effect. The measured radiative forcing at the surface from CO2 from 2000-2010 was 0.2 W/m2 from a 22ppmv increase (Feldman et al 2015) which works out at about 0.01 W/m2 per 1ppmv. However, because of the logarithmic nature of CO2’s radiative forcing, regular 1ppmv increments of CO2 would produce ever diminishing increments of radiative forcing and so 0.01 W/m2 per 1ppmv would be a generous linear relationship to use as of 2020. According to the Keeling Curve, CO2 is increasing at the rate of around 2.5ppmv/year. Therefore, the annual radiative forcing from CO2 would be about 0.025 W/m2 and that would be sufficient to raise the global temperature at the surface by about 0.0046°C under the S-B law*1 (assuming none gets absorbed in the evaporation of seawater). Far from being catastrophic, such a trivial rate of warming would be lost in the inaccuracies of the measurements.

2) The effects of CO2 are overwhelmed by water vapour. The planet’s average surface temperature is currently about 15°C while its blackbody temperature is -18°C and the temperature difference of about 33°C represents a large amount of radiative forcing by the atmospheric greenhouse. In fact it amounts to about 153 W/m2. The concentration of water vapour in the atmosphere is on average 1% (source: NASA Earth Fact Sheet) while the concentration of CO2 is 0.04%. Hence water vapour is about 25 times more abundant than CO2 in the atmosphere, and pound for pound, it also has a far greater potency than CO2 as well because it absorbs IR-energy over a much greater spectrum. CO2 comprises approximately 4% of the total atmospheric greenhouse by volume and since it is a weaker greenhouse gas than water vapour it follows logically that it cannot be contributing more than 6 W/m2 (4%) to the greenhouse effect of 153 W/m2 whereas water vapour should contribute upwards of 146 W/m2 (96%).

Water vapour is by far and away the most important greenhouse gas… even if all other greenhouse gases (such as CO2 and CH4) were to disappear, we would still be left with over 98% of the current greenhouse effect

Richard Lindzen

3) The 13C/12C ratio confirms that CO2 has a small life-time and because of this short life-time there is only a tiny percentage of human CO2 residing in the atmosphere. The atmospheric life-time for CO2 has been confirmed empirically, by observations of the atmospheric 13C/12C ratio. Around 99% of atmospheric CO2 consists of the 12C isotope with the remaining 1% consisting of 13C. The 13C/12C ratio is commonly referred to as δ13C. δ13C is the difference between the ratio of 13C/12C in a substance compared to a standard of Vienna Pee Dee Belemnite (VPDB) minus one. The number is multiplied by one-thousand and expressed as “per mil” (parts per thousand). Anthropogenic CO2 has an approximate δ13C of around –29 (with values ranging between -20 to -44) and natural biogenic CO2 is similar with a δ13C of -26. The natural atmospheric CO2 reservoir has a δ13C of around -7 when in equilibrium with dissolved CO2 in the oceans. The CO2 in the atmosphere has a δ13C of about –8.3. So, the amount of anthropogenic CO2 in the atmosphere is 6%*2 (i.e. 6% of -29 and 94% of -7) with the rest of CO2 in the atmosphere (i.e. 94%) being isotopically-indistinguishable*3 from natural sources.

4) The demonstrable impotence of atmospheric CO2 as the driver of global warming is evidenced by the fact that from 1998 to 2012 the global temperature increased at the risible rate of 0.05°C per decade (source: IPCC AR5) despite the fact humans emitted a total of 30% of our cumulative emissions since 1850 (see graph here).

5) CO2 behaves logarithmically and the more of it there is in the atmosphere the less warming each molecule should have. The logarithmic effect of CO2 is apparently due to the availability of photons of the required frequency that are absorbed. The vast majority of the warming from CO2 comes from the first 20ppmv and after that CO2 has essentially no effect (here). The insignificance of CO2 as a climate driver is corroborated by the fact that Atmospheric Emitted Radiance Interferometer measurements imply the warming from CO2 is only 0.01 W/m2 per 1ppmv (see Feldman et al 2015). That gives a warming at the Earth’s surface of [288^4+0.01/σ]^0.25-288 = 0.0018°C.*4

6) The ice-core data is not representative of true paleo-climate CO2 levels. The ice-core is not a closed-system and there are various processes that happen as CO2 is inside the ice that causes the ice to underestimate ancient CO2. Some of these processes include gravitational compression, which forces CO2 out of the ice over millennia and the high solubility of CO2 relative to N2O and O2 which is absorbed preferentially by liquid in the ice, underestimating CO2’s true values (Jaworowski 1997). Direct measurements of the surface-snow in Antarctica has shown that the surface-snow can underestimate atmospheric CO2 by up to 50% (Jaworowski et al 1992). Therefore, the ice-core is not a reliable representation of paleo-climate CO2 levels. There are chemical measurements suggesting CO2 was higher only a few hundred years ago, peaking at around 450ppmv, as shown in the graph below, adapted from Georg Beck (2007) and Stomata-proxy shows CO2 peaking at just below 450ppmv (Steinthorsdottir et al 2013). There’s different extraction methods in the ice-core to consider as well. The long-term wet-extraction method shows CO2 levels of over 900ppmv (see here).

7) The rate of warming is not unusual. The IPCC might want to explain why the global mean surface temperature increased at almost the same rate between 1860-1880, as it did between 1910-1940 and between 1975-1998 and 1975-2009 (see here). Human CO2-emissions increased by almost 3,500% from 1860-1880 to 1975-1998 and yet the rate of warming stayed essentially the same. The warming between the years 1860 to 1880 must have been natural because the Arrhenius equation for calculating radiative forcing (RF) increases from CO2 increases only gives 0.028 W/m2 of RF, or a total temperature increase of around 0.02°C — with the hypothesized positive fast feedbacks included — the data for anthropogenic CO2-emissions are from CDIAC and it can be seen here (note that the units are in ‘million metric tonnes’; to convert to CO2 multiply by 3.67 and then to convert to gigatonnes divide by 1,000). The time periods and warming trends below are from the 2010 BBC interview with Phil Jones.

8) Global warming is explainable by clouds. According to Ogurtsov et al (2012) changes in global cloudiness have increased the shortwave solar radiation reaching the surface. The increase in this shortwave forcing amounts to 3 W/m2 to 7 W/m2 (here) between 1983 to 2001 or 0.17 W/m2 to 0.39 W/m2 per year. These figures need to be divided by 2.5 to take into account the cooling effect due to a general decrease in clouds because clouds simultaneously cool and warm the Earth. For every 5 W/m2 that clouds cool the Earth by they warm it by 3 W/m2 (IPCC AR5). Thus the net-warming from the increase in shortwave solar radiative forcing (from a general decrease in cloud-cover) becomes 0.07 W/m2 to 0.26 W/m2 per year which corresponds to a warming of about 0.013°C to 0.048°C per year which corresponds to 0.13°C to 0.48°C per decade. The global surface temperature is assumed to be increasing at the rate of 0.15°C to 0.20°C per decade. So, changes in clouds could explain the warming. There’s not much room left for CO2. The idea that cloud-cover could be responsible for global warming has been further corroborated by Delgado-Bonal et al (2020) who, using NASA data, has estimated that there has been an increase in shortwave solar radiation of 3.5 W/m2 between 1984 to 2014 which was mainly determined by cloud-modulation (see graph here).

One of the most obvious ways for warming to be caused naturally is for small fluctuations in circulation patterns of the atmosphere and ocean to result in a 1% to 2% change in global cloud cover

Dr. Roy Spencer

9) The mathematical properties for the growth-rates for the human CO2-emissions and atmospheric CO2 contents are unequivocal in showing that some source other than the anthropogenic one must be contributing significantly to the atmospheric rise. Between 1990-2003 anthropogenic CO2-emissions were stable, as atmospheric CO2 accelerated away from human emissions, meaning some source other than human emissions must be driving the acceleration (see graph below from Francey et al 2013). That non-human source is presently unidentified, but we can tell that it must exist. Furthermore, from 2003-2014 anthropogenic CO2-emissions accelerated while the CO2 growth-rate remained relatively flat. So, there is a definite mismtach between our emissions and the CO2 increase. See my post here talking about a natural candidate for the CO2 increase.

10) Anthropogenic CO2 should not take hundreds or thousands of years to be removed from the atmosphere. In AR5, the IPCC say: “The removal of human emitted CO2 from the atmosphere will take a few hundred thousand years”. The Gold Standard evidence for the removal of a pulse concentration of CO2 put in the atmosphere is the measured lifetime of 14CO2! 14CO2 was in equilibrium with sources and sinks before atmospheric nuclear-testing doubled the atmospheric concentration. After the 1963 test-ban treaty stopped nuclear-testing, the pulse concentration of anthropogenic 14CO2 was naturally removed from the atmosphere with a half-life of around 10-12 years (residence time 16 years) with today’s concentration (as of 2020) approaching natural equilibrium levels. Given a half-life of 10-12 years, equilibration for the pulse 14CO2 (by ~94%) with other carbon reservoirs would take around 4 half-lives (40-48 years) which is a far cry from the IPCC’s claim of “a few hundred thousand years”. The residence time of 14CO2 of 16 years has been measured longer than that for 12CO2 possibly due to differences in the kinetic absorption and dissolution rates of the two molecules (Segalstad 2009).

11) There’s a widespread misconception that the IPCC’s AR4 and AR5 reports are based on an overwhelming amount of peer-review science. The “overwhelming mountain of peer-reviewed science” in the IPCC reports is about as real as the mythical mountain of Shangri-La. A citizen audit of the IPCC’s AR4 report found over 5,600 grey references, which included magazine articles, newspaper clippings and NGO pronouncements.

12) The predictive performance of the CAGW-models have been completely refuted by real-world observations. The graph here (from former NASA scientist Dr. Roy Spencer) shows that the IPCC’s models have massively overestimated tropospheric warming. The CAGW-models can be seen to be irrational and represent the Earth’s actual climate system so poorly they can only be described as misrepresentations of it. Quote from Dr. Roy Spencer: “We know that 95% of the models have over-forecast the warming trend since 1979, whether we use their own dataset (HADCRUT4) or our own satellite dataset of lower tropospheric temperatures (UAH)”.

13) The IPCC may have overestimated climate sensitivity.

14) A widespread misconception disseminated by the media is that humans are making hurricanes worse. Below is a graph adapted from the NOAA showing hurricanes in the USA, dating back to 1850, and there’s been no appreciable increase in the frequency of hurricanes. There has been no increase in global hurricanes either (as shown here).

15) Far from being environmentally deleterious, CO2 is a vital requirement for all life on the Earth and more CO2 would enhance the growth-rate of photosynthetic organisms. According to Donohue et al 2013: “Using gas exchange theory, we predict that the 14% increase in atmospheric CO2 (1982 to 2010) led to a 5 to 10% increase in green foliage cover in warmer arid environments”. Hence more CO2 in the atmosphere means that more plant-life will grow which means that larger populations could be sustained. That’s a good thing. Click here to see a table that shows the increase in productivity of plant-foods from a 300ppmv increase in CO2 (from Craig Idso 2013).

16) According to the IPCC, in AR5, the solar forcing since pre-industrial times has been small, amounting to only 0.05 W/m2. However, there are various reconstructions that show a large increase in TSI since pre-industrial times. Quote from Egorova et al 2018: “There is no consensus on the amplitude of the historical solar forcing. The estimated magnitude of the total solar irradiance difference between the Maunder Minimum and present time ranges from 0.1 W/m2 to 6 W/m2 making uncertain the simulation of the past and future climate”. Quote from Scafetta et al 2018: “The solar radiative forcing is quite uncertain because from 1700 to 2000 the proposed historical TSI reconstructions vary greatly from a minimum of 0.5 W/m2 to a maximum of about 6 W/m2”. One of the reconstructions below (from the book, Climate Change The Facts) shows an increase in TSI of about 4 W/m2 since 1800 which works out at a forcing of 0.7 W/m2 (since TSI is traditionally converted into solar forcing by dividing by 4 in order to take into account the spherical geometry of Earth and multiplying by an albedo of about 0.7). That is 14 times greater than what the IPCC attribute to solar forcing since pre-industrial times.

17) It’s often claimed by CAGW-alarmists that the modern sea level rise is alarming and unprecedented, thus implying that human activity must be responsible. This is another misconception. The global sea level has been rising long before human CO2-emissions became a significant factor — post-1950 (see graph below). The sea level rise pre-1950 must have been naturally-caused because human CO2-emissions were pretty negligible (as shown here). Whatever natural factors caused the sea level to rise between 1880 to 1950 could have still been at play post-1950. About 50% of human CO2-emissions have occurred after 1990. The graph below shows that the sea level has not accelerated as human CO2-emissions increased and the modern sea level rise is well-within long-term natural variation. So, how do we know that what is happening with the sea level rise is not just Mother Nature rolling on with natural cycles as she has done for eons?

18) Compelling evidence the IPCC’s models misrepresent the Earth’s climate is shown in the graph below. The IPCC’s climate models predict that as atmospheric CO2 and other greenhouse gases increase then the outgoing longwave radiation (OLR) will decrease as more radiation is trapped and re-radiated back towards the surface. The graph below (from Lindzen et al 2009) is a compelling refutation of the CAGW-hypothesis and shows that OLR has not increased as the models have predicted. This shows that the climate models trap heat too aggressively. The vertical axis in the graph below is OLR and the horizontal axis is sea-surface temperature. The red line is from the ERBE satellites and the green line are the IPCC’s model predictions. The ERBE satellite shows the opposite to what the models have predicted, that is, that more radiation is being re-radiated out to space as the temperature rises and is not being trapped as the models predict.

The climate models are violently at odds with reality

David Evans

19) Another widespread misconception is that (the mythical planet) Venus is hot due to the radiative enhancement from its high atmospheric CO2 concentration (96.5%). This claim is dubious and due to Venus’ high albedo, there is insufficient solar energy that the planet absorbs to drive a powerful greenhouse effect. Venus is estimated to have a solar irradiance of 2600 W/m2 and its bond albedo is usually cited to be between 0.75 to 0.80 (Colin 1983) but other observations and sources indicate a higher bond albedo of 0.90 (see Mallama et al 2006 and Tian et al 2013). We can use the equation here to calculate the effective blackbody temperature of Venus, assuming a solar irradiance (Iₒ) of 2600 W/m2 and a bond albedo (ᴬB) of 0.90.

Where T is the effective blackbody temperature, Iₒ is the solar irradiance or solar constant, ᴬB is the bond albedo, and σ is the Stefan-Boltzmann constant. Plugging the values into the equation, we get 65 W/m2 of absorbed solar radiation which would only be enough to raise the surface temperature of Venus to 184K. However, we find that the surface temperature of Venus is 740K (according to NASA), requiring a radiative enhancement by the atmospheric CO2-greenhouse of ~16,000 W/m2 (by the S-B law*1). Yet Venus absorbs 65 W/m2 of solar radiation (or 160 W/m2 assuming an albedo of 0.75). For the greenhouse effect to operate, the atmosphere of a planet needs to be relatively transparent to incoming shortwave solar radiation and relatively opaque to outgoing longwave radiation. However, due to Venus’ high albedo, this is not possible. Something else on Venus must be causing its high temperature, such as adiabatic compression.

20) The threat from methane has been overblown. The graph here adapted from Barret (2005) show the absorption characteristics of the main atmospheric greenhouse gases. Water vapour is the top, methane is second, and CO2 is third. T0 means all radiation is absorbed and T1 means nothing is absorbed. Strong absorbance from methane occurs at wavenumbers around 1300 cm⁻¹. CO2 absorbs radiation strongly at around 670 cm⁻¹ and 2350 cm⁻¹, while water vapour absorbs strongly over much of the electromagnetic spectrum. We can see from the graph below that methane is rather weak at absorbing radiation when compared to water vapour. Methane exists as a tenuous trace gas, and comprises about 1.9ppmv of the atmosphere (as of 2020) whereas water vapour makes up about 10,000ppmv (NASA Earth Fact Sheet) making water vapour 5,000 times more abundant than methane while being more efficient at absorbing radiation. Methane is a trivial greenhouse gas and its effects are completely overwhelmed by water vapour. The current methane concentration of 1.9ppmv corresponds to around 5 gigatonnes (Gts); about 0.38ppmv per 1 Gt. Assuming the permafrost melted and it added an extra 5 Gts to the atmosphere by 2100 (IPCC AR5: Biogeochemical Cycles, page 530 to 531) then that would only increase the concentration of methane by 1.9ppmv, which is still 5,000 times less abundant than the concentration of water vapour. Methane only makes up 1 molecule in every 500,000 molecules spread evenly throughout the atmosphere.

The IPCC’s formula below can be used to determine how much radiative forcing a given increase in CH4 would have. Where ΔF stands for the ‘increment of radiative forcing’ in W/m2; M is the new CH4 concentration in ppbv after the increment is added, and M₀ is the old CH4 concentration before the increment was added.

Accepting that the current CH4 concentration is around 1900ppbv (as of 2020) and that the IPCC claim another 1900ppbv will be added to the atmosphere by 2100 due to the melting permafrost (total of 3800ppbv) then that would give us a radiative forcing from the released CH4 of 0.036(√3800−√1900) = 0.65 W/m2 which would only be enough to raise the surface temperature by 0.12°C. And that is on the basis of their own figures! It makes you wonder how people can justify ‘the sky is falling’ hysteria about CH4.

21) It’s claimed the increase in CO2 is causing the ocean to acidify at an unprecedented rate and this will cause harm to coral reefs and marine life. Firstly, the term ‘acidify’ is a misnomer, because the current average ocean pH is assumed to be between 7.9 to 8.0 (depending on the source) below an assumed pre-industrial level of 8.2 and that is very much alkaline. Secondly, while humans are assumed to have contributed to the change in ocean pH, it can change naturally, and has done so in the past, due to things such as temperature, eutrophication and biological activity. The graph here (from Pelejero et al 2005) is based on paleo-climate reconstructions and it shows the rate of change of pH going back 300 years and we can see that pH changed naturally and rapidly long before humans started emitting CO2. The graph in the link above shows that between 1710 to 1750 and 1815 to 1845 ocean pH decreased by about 0.05 units per decade while the modern decrease in pH as measured at Hawaii is around 0.033 units per decade. Hence the rate of modern decrease in pH is not unusual and is within natural variation.

This image has an empty alt attribute; its file name is graphic.PNG

22) Here is a video from PragerU explaining various alarmist AGW misconceptions, with one of them being that global droughts are not increasing, according to a Nature study (Hao et al 2014). See graph here.

*1 The Stefan-Boltzmann law

*2 Assuming a pre-industrial δ13C value of -6.5 instead of -7, we get a total amount of 8% of human CO2 in the atmosphere instead of 6%

*3 If there were more than one source for the CO2 increase then the human component could be more or less than 6% due to the anthropogenic signature being mixed up with negative and positive δ13C values of CO2 emissions from other sources. A decrease in δ13C is not a unique signature of anthropogenic CO2 and natural CO2 depleted in 13C like biogenic CO2 or bacteriogenic methane (which oxidizes to CO2) would decrease δ13C and there is evidence that this has occurred naturally in the past

*4 This tiny warming by CO2 is corroborated by Stallinga 2020 who calculates climate sensitivity to rising CO2 concentrations of 0.0014°C per 1ppmv


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