Natural variation trumps CO2
Many climate scientists claim that our carbon dioxide emissions are the principal driver of global warming. I have asked several University of Arizona professors, who make such a claim, to provide supporting physical evidence. So far, none have been able to justify the claim with physical evidence.
In this article, we will examine the Earth’s temperature and the carbon dioxide (CO2) content of the atmosphere at several timescales to see if there is any relationship. I stipulate that the greenhouse effect does exist. I maintain, however, that the ability of CO2 emissions to cause global warming is tiny and overwhelmed by natural forces. The main effect of our “greenhouse” is to slow cooling.
There is an axiom in science which says: “correlation does not prove causation.” Correlation, however, is very suggestive of a relationship. Conversely, lack of correlation proves that there is no cause-and-effect relationship.
Estimates of global temperature and atmospheric CO2 content based on geological and isotope evidence show little correlation between the two. Earth experienced a major ice age in the Ordovician Period when atmospheric CO2 was 4,000ppm, 10 times higher than now. Temperatures during the Cretaceous Period were rising and steamy, but atmospheric CO2 was declining.
Notice also, that for most of the time, Earth’s temperature was much warmer than now and life flourished. There were some major extinction periods, all associated with ice ages.
- Berner, R.A., and Kothavala, Z, 2001, GEOCARB III: A Revised Model of Atmospheric CO2 over Phanerozoic Time, American Journal of Science, Vol. 301, February 2001, P. 182–204
- Scotese, C.R., http://www.geocraft.com/WVFossils/Carboniferous_climate.html
During the latter part of our current ice age, glacial-interglacial cycles occurred with a periodicity of about 100,000 years which correlates with the changes in Earth’s orbit around the sun as it changes from nearly circular to elliptical with an eccentricity of about 9%. Here we see an apparent correlation between temperature and CO2. The data are from ice cores collected at the Vostok station in Antarctica. The scientists working on the Vostok core noticed that temperature changes PRECEDED changes in CO2 concentration by about 800 years. Again, we see that CO2 doesn’t have much influence on temperature, but the temperature has great influence on CO2concentration because temperature controls CO2 solubility in the ocean.
- Petit, J.R., et al., 1999. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399: 429-436.
- Mudelsee, M, 2001. The phase relations among atmospheric CO2 content, temperature and global ice volume over the past 420 ka, Quaternary Science Reviews 20:583-589.
- Siegenthaler, U. Et al., 2005. Stable carbon cycle-climate relationship during the late Pleistocene. Science 310: 1313-1317.
The Holocene represents the current interglacial period. For most of the past 10,000 years, the temperature was higher than now. CO2 was fairly steady below 300ppm (vs over 400ppm now). There were cycles of warm and cool periods at a periodicity of 1200 to 1500 years. This periodicity correlates with the interplay of the several solar cycles. The sun itself goes through cycles of solar intensity and magnetic flux. When the cycles are in a strong phase, the strength of the cosmic rays entering our atmosphere is reduced, and there are fewer clouds to block the sun, making it warmer.
When solar cycles wane, as is beginning to happen now, more cosmic rays enter the atmosphere and produce more clouds which block the sun, so it becomes cooler. The number of sunspots (hence magnetic flux) varies on an average cycle of 11 years. There are also 87-year (Gliessberg) and 210-year (DeVriess-Suess) cycles in the amplitude of the 11-year sunspot cycle which combines to form an approximately 1,500-year cycle of warming and cooling.