Ralph Bush, in his April 20 letter, seems to have misinterpreted the science he holds in such high regard. The latest dendrochronology study of 2,000 years of tree ring data did indeed suggest that the climate has fluctuated in the past between warmer and cooler periods, based upon natural factors such as volcanoes and shifts in the orbit of the earth. This was not the new information produced by the study.
Moreover, Robert Wilson, a paleoclimatologist who co-authored the study, said, None of this changes the fact that the current warming cant be modeled based on natural forces alone. ... Anthropogenic emissions are the predominant forces in the late 20th century and early 21st century period. And as for the validity of those models, its true that they are not always correct: The models appear to have significantly underestimated the rate at which the earth is warming, giving us a shorter window of time in which to act to reverse it.