Re: "Denier Debunked" by Steve Ghan (Letters, July 29)
Mr. Ghan cites ice cores as showing remarkable correlation of temperature with CO2 over an 800,000-year period with 8-degree ice age swings. If you look at the data closely there are periods where temperature rise does not correlate with CO2 at all. For example, the Vostok ice cores 125,000 years ago show over a 15,000 year period a drop in temperature of about 8 degrees with no essential change in CO2. Similarly in the Greenland data there are periods where CO2 actually lags temperature change. Hence, it could not be the cause of the change for this period.
Today the IPCC says that we are heading for potential catastrophe because man-made CO2 may cause a 2 degree increase in global temperature by 2050. This is based on computer models that are not well benchmarked, overstate positive feedbacks and cannot pick up variations in the CO2/temperature correlations found in, for example, the ice core data.
Is the planet warming slightly? Yes, as part of a normal cycle coming out of the last ice age. Is man the cause of this warming? No, if the basis of this conclusion is the climate models -- it is the sole basis -- and heck no, as justification for a $1 trillion carbon tax by 2030 to fix it.
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CRAIG BROWN, Richland