An individual named Martin Hertzberg did a grave disservice to your readers by making false and defamatory statements about me and my climate scientist colleagues in his recent commentary in your paper.
It's hard to imagine anyone packing more lies and distortions into a single commentary. Mr. Hertzberg uses libelous language in characterizing the so-called "hockey stick" -- work of my own published more than a decade ago showing that recent warming is unusual over at least the past 1,000 years -- as "fraudulent," and claiming that it "it was fabricated from carefully selected tree-ring measurements with a phony computer program."
These are just lies, regurgitation of dishonest smears that have been manufactured by fossil fuel industry-funded climate change deniers, and those who do their bidding by lying to the public about the science.
The highest scientific body in the nation, the National Academy of Sciences affirmed my research findings in an exhaustive independent review published in June 2006 (see e.g. "Science Panel Backs Study on Warming Climate," New York Times, June 22, 2006, among many others).
Dozens of independent groups of scientists have independently reproduced and confirmed our findings, and more recent work by several groups shows that recent warmth is unusual over an even longer time frame.
Mr. Hertzberg then continues the smear by lying again about my work, claiming that "when those same tree-ring data actually showed a decline in temperature for the past several decades, Mann and his co-authors simply 'hid the decline' by grafting direct measurements (inadequately corrected for the urban heat island and other effects) to his flat tree-ring line."
That is, once again, a string of lies tied together. This statement falsely equates my work, which was not based on tree rings but rather a diverse network of different types of "proxy" climate data, with tree-ring work by an entirely different scientist, Keith Briffa of the University of East Anglia.
And it is is a highly dishonest characterization of his Briffa's work, as well, since the "decline" was a well-known problem with those particular data that Briffa was the first to describe and attempt to deal with, in the scientific literature.
Mr. Hertzberg's lies are pernicious. Their intent appears to be to do convince you that there is no harm in our continued unfettered release of carbon into the atmosphere.
It is not only us, but our children and grandchildren who will suffer the consequences of devastating changes in our environment in the years and decades to come if we listen to charlatans like Mr. Hertzberg.
Readers interested in the truth behind the science, rather than the falsehoods and smears perpetuated by people like Mr. Hertzberg, should consult the scientist-run website www.realclimate.org and www.skepticalscience.com, or scientifically-based books on the topic like my "Dire Predictions: Understanding Global Warming."
Michael E. Mann is a professor in the Department of Meterology at Penn State University and director of Penn State Earth System Science Center.