Vail Daily letter: No causal relationship |

Vail Daily letter: No causal relationship

Whoa! My letter (Jan. 7) questioning human caused global warming science seems to have caused greenhouse gas emotions to rise in two Eagle households (Letters to the Editor, Jan. 12 and 13).

Again, I know of no one who would dispute that climate is changing. Regardless of whether or not certain factions believe that because we’re here to see it and measure it that we must be causing it, is no reason to accept a hypothesis unsupported by actual evidence. Computer simulations are not evidence.

As a chemist I do admit I enjoy stirring the flask to engage others in discussions of this topic. But, I confess amazement when people pushing the warmist point of view are threatened by disagreement and resort to innuendo and name calling. That said, this arrogant frog will hold no resentment for such actions. I am old and have long since learned that holding on to resentment is like drinking poison and then waiting for someone else to die. So, let us get on with the discussion.

Of the questions that I asked before, the most important was “what CO2 concentration is required to support plant life?” That answer is 150 parts per million. Modern plant life evolved during a time when CO2 concentrations averaged over 1,500 parts per million. At 180 parts per million plants are surviving on a starvation level of CO2. At 400 parts per million they are malnourished. Experimental evidence suggests that a much better level for plants is 1,500 parts per million. Experiment suggests that the growth enhancement for crops from increasing present levels to 600 ppm is over 100 percent and an increase to 1,200 parts per million would enhance crop yields by over 200 percent.

On the question of what the optimum temperature for human flourishing is, the short answer is that no one knows. We do know that humans evolved as a tropical species, so I doubt that warmer will hurt. We also know that humans did quite well during the medieval warm period when average global temperatures were over one degree centigrade higher than now. Vikings could sail across the North Atlantic and could farm on the coasts of Greenland and Newfoundland. At the present rate of temperature rise it will take two centuries to get back to the temperature of that period.

Claims that CO2 is a causative agent in climate change are not substantiated by evidence. For most of the last 500 million years temperature and CO2 levels have risen and fallen independently of each other. There is no identifiable causal relationship there. More recently over the last 300,000 years or so changes in CO2 levels have lagged behind temperature changes by an average of 800 years. In this last case, it is more accurate to say that temperature change caused the CO2 level to change through increasing and decreasing levels of ocean outgassing. This outgassing is the largest source of atmospheric CO2.

To repeat, no one denies that climate is changing. What I and many others deny is that CO2 (and thus human activity) is a significant causative agent. We can of course agree to disagree. For a more complete discussion of this issue please read through the material at

Tom Chastain


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