Most media articles about global warming or climate change are written with the acceptance of carbon dioxide (CO2) as the cause.  I have no bias as to whether there is climate change or if CO2 is the cause, but I am a humble scientist who understands the basic chemistry and physics and demands proof of cause, especially when radical solutions are being proposed that will affect us all in highly significant ways.  So far, the case for blaming CO2 is not convincing.

There are few articles available that present the whole CO2 case in a balanced, comprehensible way.  Two that are worth reading are "The Clouds of Unknowing" (The Economist, 3/20/2010) and "Global Warming and Climate Change" (Chemical and Engineering News, 12/21/2009).  These and other sources raise numerous awkward questions that need to be addressed by the accusers of CO2, including:

CO2 Molecule (credit: Jynto).

• Why does the minute 100-parts-per-million (ppm) increase in CO2 have such an impact on warming?  CO2 concentrations in our air have increased over the last century from 0.03% to 0.04%, a rise of about 0.01%, or 100 ppm — that is, one part in 10,000.  It is the impact of this tiny increase that needs to be explained by advocates of human-induced warming.  Over geological time, CO2 has reached atmospheric levels up to about 8,000 ppm, cycling with various geological events.  The current 400 ppm is at the low end of the average over millions of years.
• Why is CO2 currently the cause of warming when there have been cooling and warming cycles before, not related to CO2?
• Why is the minute effect of CO2 significant when the impact of water as a greenhouse gas is about 250 times greater?  CO2 is a greenhouse gas, but, due to its low concentration and potency, its contribution is insignificant compared to water, the major greenhouse gas in our atmosphere.  Adjusting for water's four times greater greenhouse gas potency than CO2 and taking its average concentration in our air as 2.5%, or 25,000 ppm, increases its influence on warming to about 250 times more than the 400-ppm CO2 and about 1,000 times more than the 100-ppm increase in CO2.  Don't the natural fluctuations in water levels swamp the minute contribution of CO2 to warming? 
• Are the models of climate scientists credible when they treat water as a feedback and not as a forcing in their models?  Their rationale is that water forms clouds above the surface of the Earth that have a different effect on warming.  Clouds actually increase warming due to their insulation effect.
• Are we better off with higher CO2 levels since they accelerate plant growth?  CO2 has a vital role as the raw material for the growth of all green plants by photosynthesis, which we depend on for our nutrition and our oxygen.  This acts as a natural regulator of CO2 levels in the air.  Plants grow faster in higher CO2 concentrations, which would help to feed the world, and they also produce more oxygen, which we need to live.  To call CO2 a pollutant is disingenuous.
• Finally, are warnings of the effect of warming on serious weather events and rising sea levels credible?  Data do not support substantial increases in unusual weather events like hurricanes and storms in recent times. Further, warming would probably not significantly raise sea levels.  Water expands about 10% on freezing and shrinks on melting (this is why water pipes burst on freezing/melting), and it expands slightly on warming when liquid.  There will be a rise in sea levels only if most of the melting ice is above sea level and the water warming is much more than a few degrees, an unlikely scenario.  Warming is unlikely to cause the rising sea calamities that are threatened.

The last sentence in the Economist's 2010 article reads: "The doubters are right that uncertainties are rife in climate science.  They are wrong when they present that as a reason for inaction."  The first part is correct, but the second part is not, as I hope my comments show.  There are a lot of others like me who need to see CO2 proven guilty before we upend society in the ways that are proposed.  And if it is innocent, let's find the real culprit, assuming that there is a warming crisis and that warming would be bad for us.

Terence Winters, Ph.D. is the retired CEO of a publicly listed biotechnology company.