Dr. David Evans:
Now that ClimateGate has buried the fraudulent hockey stick for good, it is easy to prove that global warming is not man-made: just compare the timing of our carbon dioxide emissions with the timing of global warming.
Human Emissions of Carbon Dioxide
Emissions of carbon dioxide by humans are easy to estimate from our consumption of coal, oil, and natural gas, and production of cement:
Figure 1: Carbon emissions by humans. Source: Carbon Dioxide Information Analysis Center. The vast bulk of human emissions occurred after 1945, during post-WWII industrialization. Half of all human consumption of fossil fuels and cement production has occurred since the mid 1970s.
Temperatures
Global temperature proxies (sediments, boreholes, pollen, oxygen-18, stalagmites, magnesium to calcium ratios, algae, cave formation, etc. over a wide geographical range) show a warming trend starting around 1700, with warming and cooling periods about the trend:
Figure 2: Mean global temperature reconstruction based on 18 non-tree-ring proxies, to 1935. Only 11 proxies cover the period after 1935, dotted line. Sources 1, 2, 3, 4: Dr Craig Loehle, National Council for Air and Stream Improvement. Global thermometer records are more reliable and precise, but only go back to 1880. They confirm that the warming trend extends back to at least 1880, and show warming and cooling periods of about thirty years in each direction:
Figure 3: The global instrumental temperature record to 2000, in the yellow box. Simply draw a trend line through the data. In 2009 we are where the green arrow points. . Source: Dr Syun Akasofu, International Arctic Research Center, University of Alaska Fairbanks. Compare the Timing
The timing is all wrong for the theory of manmade global warming:
- Temperature increases started in 1700, and the underlying rate of increase has been roughly steady (though there have been warming and cooling fluctuations around the trend).
- Human emissions of carbon dioxide were negligible before 1850, and really only took off after 1945.
If human emissions of carbon dioxide caused global warming, then there would be massive and accelerating global warming after 1945 and almost no global warming before 1945. Obviously this is not the case.
Conclusions
- There is almost no relationship between human emissions and global temperature, so global warming is not mainly due to human emissions of carbon dioxide.
- Something other than human emissions caused the global warming prior to 1850.
- The steadiness of the underlying temperature trend since 1700 suggests that whatever caused the warming prior to 1850 is still causing warming, and that the effect of human emissions of carbon dioxide is relatively insignificant.
QED
Notes
- This only proves that the recent global warming was not mainly due to human emissions of carbon dioxide. It does not rule out all possible man-made influences, but since the popular debate is overwhelmingly about the role of our carbon dioxide emissions this simplification is justifiable in this context.
