Princeton physicist Will Happer wonders what the optimum level of carbon dioxide is:
We conclude that atmospheric CO2 levels should be above 150 ppm to avoid harming green plants and below about 5000 ppm to avoid harming people. That is a very wide range, and our atmosphere is much closer to the lower end than to the upper end. The current rate of burning fossil fuels adds about 2 ppm per year to the atmosphere, so that getting from the current level to 1000 ppm would take about 300 years—and 1000 ppm is still less than what most plants would prefer, and much less than either the nasa or the Navy limit for human beings.
The Hockey Stick Illusion is mentioned too:
The IPCC and its worshipful supporters did their best to promote the hockey-stick temperature curve. But as John Adams remarked, “Facts are stubborn things, and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence.” The hockey-stick curve caught the attention of two Canadians, Steve McIntyre, a mining consultant, and an academic statistician, Ross McKitrick. As they began to look more carefully at the original data—much of it from tree rings—and at the analysis that led to the hockey stick, they became more and more puzzled. By hard, remarkably detailed, and persistent work over many years, consistently frustrated in their efforts to obtain original data and data-analysis methods, they showed that the hockey stick was not supported by observational data. An excellent, recent history of this episode is A. W. Montford’s The Hockey Stick Illusion.