This post is to highlight conclusions from a 1998 paper by Sherwood B Idso in Vol 10: 69-82 of Climate Research, "CO2-induced global warming: a skeptic’s view of potential climate".
Sherwood Idso finds that a consensus of 8 natural experiments he describes is that for a doubling of carbon dioxide to 600ppm, the global temperature might rise at most by 0.4 degrees C.
To save blog space the links below take readers to the relevant sections of an html version of Sherwood Idso’s paper.
2.1. Natural Experiment 1
The first of the unique meteorological situations investigated was the change in atmospheric water vapor that typically occurs at Phoenix, Arizona, USA, with the advent of the summer monsoon.
2.2. Natural Experiment 2
With respect to the phenomenon of naturally-occurring vertical redistribution of dust that occurs at Phoenix, Arizona, each year between summer and winter, (Idso & Kangieser 1970), Sherwood Idso had previously demonstrated that the restriction of airborne dust to a much shallower depth of atmosphere during winter does not alter the transmittance of the atmosphere for the total flux of solar radiation, but that it increases the atmosphere’s downwelling flux of thermal radiation at the Earth’s surface by
13.9 W m –2 (Idso 1981b).
2.3. Natural Experiment 3
The annual cycle of surface air temperature that is caused by the annual cycle of solar radiation absorption at the Earth’s surface was studied at 81 locations within the United States.
Discussion 2.4. Initial implications
2.5. Natural Experiment 4
The first of two 2 global-equilibrium natural experiments consisted of simply identifying the mean global warming effect of the entire atmosphere and
dividing it by the mean flux of thermal radiation received at the surface of the Earth that originates with the atmosphere and which would be non-existent
in its absence.
2.6. Natural Experiment 5
The second global-equilibrium experiment made use of the annually-averaged equator-to-pole air temperature gradient that is sustained by the annually-averaged equator-to-pole gradient of total surface-absorbed
radiant energy (Idso 1984).
Discussion 2.7. Intermediate implications
2.8. Natural Experiment 6
Considering what could be learnt from our nearest planetary
neighbors, Mars and Venus.
2.9. Natural Experiment 7
The same result may also be obtained from the standard resolution of the paradox of the faint early sun
(Sagan & Mullen 1972,
2.10. Natural Experiment 8
A final set of empirical evidence that may be brought to bear upon the issue of CO2 -induced climate change pertains to the greenhouse effect of water vapor over the tropical oceans.