There is no denying that the atmospheres of Earth and Venus are responsible for a "greenhouse effect" that raises their surface temperatures significantly above their black body or effective temperatures. However, claims by anthropogenic global warming (AGW) alarmists about excess CO2 being responsible for temperature anomalies in the order of 1 °C are contradicted by the fact that Mars has more CO2 than Earth, but has no greenhouse effect.
Data is mostly sourced from NASA. The solar irradiance at 1 astronomical unit (AU) from the Sun is taken as 1,366 W/m2, from World Radiation Center measurements. For the other orbital radii of Mercury, Venus and Mars, an inverse square law adjustment is applied. Since we want to obtain the average solar flux received over the entire planet's surface as opposed to at some point where the Sun is directly overhead, the figure is then divided by four, being the ratio of the surface area of a sphere to its cross-section. In order to obtain the absorbed radiation after allowing for reflected sunlight, the solar irradiance per square meter of the planet's surface is multiplied by a factor of one minus its Bond albedo. The effective temperature, i.e., the temperature of a black body emitting the same flux as the absorbed radiation and hence in thermal equilibrium, is calculated from the Stefan Boltzmann law according to:
T = [Pd / σ]1/4 where T is the absolute temperature (K), Pd is the flux or power density (W/m2), and σ is the Stefan-Boltzmann constant of 5.6703×10-8 W/m2.K4.
Mercury's atmosphere is essentially a vacuum, and so the mean surface temperature equals the effective temperature, although there is of course a large difference between the sun-facing side and the regions experiencing a long night. For the next three planets, it may be seen that the excess temperature over the effective temperature is more strongly correlated with the quantity of all atmospheric gases, or with the nitrogen, rather than the so-called greenhouse gases CO2 or H2O. At 210 K, Mars has the same mean surface temperature as its effective or black body temperature. Yet it has 167.6 kg/m2 of CO2, which is 28.1 times the 5.96 kg/m2 for Earth, which has an excess temperature of some 34 K or 13.3% over its black body temperature. But Venus has 1,021,000 kg/m2 of CO2, which is 171,000 times the value for Earth, whilst the surface temperature of Venus is 737 K, which is 4 times its black body temperature.
The proportions of each gas are generally quoted by volume, so these values were adjusted by a factor comparing the molecular mass of the gas with the molecular mass of the planet's atmosphere, to find the mass quantity for each gas. Water vapor on Earth is reckoned to average about 1% by volume albeit highly variable, whereas H2O has a molecular weight of 20.04 compared to the average MW of 28.97 for Earth's air, so the mass fraction is taken as 0.69%.
|Effective temp. or
black body temp.
|440 K||184.2 K||254.2 K||210 K|
|440 K||737 K||288 K||210 K|
|Surface temp. /
black body temp.
|Volumetric mean radius
Total surface area
|Mass of CO2||Possible trace amounts; negligible||4.7E20 kg
|Mass of H2O||Possible trace amounts; negligible||3.98E15 kg
|Mass of N2||Possible trace amounts; negligible||
|Mass of O2||<~8.5E-12 kg/m2; negligible||None||1.18E18 kg
When faced with the example of Mars, the global warming alarmist will typically reply that Mars has no greenhouse effect because it has only about one-hundredth the atmosphere of the Earth. Yes, but it still has around 28 times as much CO2 per square meter column of its atmosphere compared to Earth!
It is interesting that the warming effect on Venus raises its temperature to four times its black body temperature, but this is probably mere coincidence. If Venus is so saturated with CO2 that increases in levels had stopped leading to any further temperature rise long ago, a fourfold limit on the absolute temperature rise would not derive from a geometric effect, such as compensating for the fourfold reduction in flux over the surface area of a sphere compared to the incident flux on the cross-sectional area of the planet facing the Sun. A four-fold increase in black body temperature corresponds to a 44 times or 256 times increase in flux.
And the four-fold temperature increase on Venus is after allowing for its Bond albedo being much higher than the other planets at 0.9, so that only 10% of the incoming radiation is assumed to be absorbed for purposes of calculating Venus's black body temperature. If Venus had the same Bond albedo of Earth, say, at 0.306, then its absorbed radiation before any greenhouse effect increases from 65.33 to 453.4 W/m2, raising its black body temperature from 184.2 to 327.6 K. So in this case the warming to 737 K is a temperature rise of 2.25 times instead of 4 times, and again with 171,000 times as much CO2 as on Earth.
A model that attempts to quantify how much of each gas would lead to a rise of, say, 10% in absolute temperature works best when CO2 is deemed to be relatively insignificant as a greenhouse gas. A simple program was written in which various values for CO2, H2O, N2 and O2 were inputted as the assumed amount in kg/m2 that would lead to a 10% increase in temperature (corresponding to a 46.41% increase in net flux absorbed). For each planet, the actual values (kg/m2 ) of each gas from the above table were assigned, with the final predicted increase being the product of four factors: 1.1 raised to the power of each assigned value divided by the inputted value assumed to produce a 10% temperature rise. For example, if the actual CO2 level was twice the assumed amount necessary for a 10% temperature rise, the increase would be a factor of 21% for that gas, and if another gas was at the level assumed to give a 10% increase, the overall increase would be 1.21 times 1.1 times whatever factors were obtained for the other two gases.
In all cases the values of each gas on Mercury was taken as sufficiently low in relation to that required for any greenhouse effect that a value of zero could be assigned for each gas, with the predicted surface temperature to black body temperature being a ratio of 1.0. The first result in agreement with the observed values for the other planets assumed 89,208 kg/m2 for the amount of CO2 required to raise the temperature by 10%, and 7,577 kg/m2 for each of H2O, N2 and O2 to raise the temperature by 10%. With these inputted values, the predicted increase was 4.0010 for Venus, 1.1330 for Earth, and 1.000219 for Mars.
If we suppose that the "correct", pre-industrial level for CO2 on Earth is 284 ppm by volume, and 2011 is up to 392 ppm, then that is multiplied by 44.01 / 28.97 (the ratio of the molecular weights of CO2 and air) to get the mass fractions of 431 ppm and 596 ppm respectively. Thus, the man-made increase is 165 ppm by mass, which taking Earth's atmosphere as 5.1E18 kg is an increase of 8.415E14 kg or 1.65 kg/m2 of CO2. If 89,208 kg/m2 of CO2 is required for a 10% rise in temperature, then 1.65 kg/m2 of CO2 would lead to a temperature rise of 1.11.65/89208 = 1.000001763 times, or an increase of 0.0005077 K on Earth's 288 K.
In order to increase CO2's potency as a "dangerous" greenhouse gas, it is necessary to start ignoring the predictions for Venus by the addition of a postulate about carbon dioxide levels being saturated or close to saturation there. Given this proviso, when we assume 7,583 kg/m2 is required for each of the four gases to bring about a 10% increase in absolute temperature, the predicted increase for Venus is an absurd 503,006 (but limited to 4 by the additional postulate), with 1.13300 for Earth and 1.00215 for Mars. So in this case, the extra 1.65 kg/m2 of CO2 would lead to a temperature rise of 1.11.65/7583 = 1.000020739 times, or an increase of 0.005973 K on Earth's 288 K.
By the time Venus has warmed up to a surface temperature of 737 K, its peak emission wavelength has shifted down to 3.93 μm, from 15.73 μm (at the 184.2 K effective temperature with no global warming). At 737 K the intensity radiated at 15 μm, around CO2's broadest peak absorption wavelength, is 58.641 W/m2/sr/µm compared to the 890.589 W/m2/sr/µm at the peak wavelength. But even if CO2 absorption was zero at shorter wavelengths - which it isn't, as can be seen in the plot below, a reduction of around 15 times would not account for Venus having a temperature rise of only eleven times greater than Earth whilst having 171,000 times a much CO2. Thus, the postulate about saturation is still required. On the other hand, in the case of Mars, at 210 K its peak emission wavelength is 13.7988 µm compared to Earth's 10.0616 µm at 288 K. With Mars' infra-red emission being closer to CO2's main absorption band, not only does Mars have 28 times as much CO2 for each column of air compared to Earth, but the greenhouse effect per kg of CO2 should be greater on Mars than on Earth.
When CO2 and H2O are assumed to be ten times as important as nitrogen and oxygen in the greenhouse effect, then setting the CO2 and H2O requirement for a 10% temperature rise at 810 kg/m2 and the corresponding N2 and O2 levels at 8,100 kg/m2 predicts an even more absurd increase of 1.98E52 for Venus, 1.13297 for Earth and 1.01996 for Mars. The increase for Mars is only a few K, so is probably acceptably low. In this case, then, the extra 1.65 kg/m2 of CO2 would lead to a temperature rise of 1.11.65/810 = 1.000194169 times, or an increase of 0.05592 K on Earth's 288 K.
If CO2 and H2O are assumed to be a hundred times as important greenhouse gases as nitrogen and oxygen, then values of 132 kg/m2 for CO2 and H2O to cause a 10% temperature rise, and 13,200 kg/m2 as the corresponding values for N2 and O2, predicts 1.75E320 as the unadjusted increase for Venus, 1.13351 for Earth, and 1.12868 for Mars. So this can be safely ruled out since the predicted increase on Mars is inconsistent with observations.
When CO2 is ten times as important as N2 and O2, and H2O is ten times as important as CO2, then taking 1,280 kg/m2 of CO2 to produce a 10% rise in temperature, 128 kg/m2 as the requirement for H2O, and 12,800 kg/m2 for N2 and O2 predicts an increase of 1.2E33 times for Venus, 1.3342 for Earth, and 1.01259 for Mars. In this case the extra 1.65 kg/m2 of CO2 would lead to a temperature rise of 1.11.65/1280 = 1.000122868 times, or an increase of 0.03539 K on Earth's 288 K.
Oxygen and nitrogen are "greenhouse" gases, since their main absorption bands are 6-7 μm and 4-5 μm respectively, which is closer to the 288 K Earth's peak infra-red emissions of 10 μm than to the Sun's 0.5 μm.
In contrast, the absorption of CO2 covers a wide band extending almost to the optical range (see the first plot).
Given that Earth's atmosphere has much more nitrogen and oxygen than CO2, and Mars has much more CO2 than Earth but not even the slightest greenhouse effect, it is obvious that the vast majority of Earth's greenhouse effect derives from N2 and O2 rather than CO2.
The doom-mongers' claims of man-made global warming in the order of 1 K are a combination of over-hyped hysteria and blatant lies, which have been concocted and whipped up in order to benefit politicians in the short-term via pretexts for raising taxes, certain scientists in the short-term who promote the hoax and so are likely to receive plenty of funding, and to benefit bankers in the long-term by the interest on the inexorably rising massive levels of debt as the world economy is damaged by the shameful waste of countless trillions of dollars. The effect is to hit the world's poor disproportionately, with the winners being the rich, powerful, and the false prophets.
Any honest, independent researcher who is not being funded by those with ulterior business or political interests will soon find that so-called "anthropogenic global warming" is junk 'science', like homeopathy. For example, Al Gore's movie on "global warming" has already been proven to be riddled with dozens of errors whilst being short on facts. Historic CO2 levels lag global air temperatures, and so cannot be a primary driver of climate change.
Amusingly, the IPCC's bogus "scientists" have proposed a novel ad hoc 'theory' that is supposed to account for the slowdown in increasing surface temperatures since 1998 whilst CO2 levels continue to increase. They claim that the heat is not missing, but it's hiding deep beneath the sea. Thus, if schoolchildren are going to be taught about "man-made global warming", they will have to stop teaching them about convection currents and about water's high heat capacity relative to air.
It is time to stop the climate change alarmists' preposterous political agenda and business scam before the damage incurred is sufficient to impoverish humankind for hundreds of years.