After writing 10 columns on the subject, one for each "denier" and his theories, one fact is undeniable: The science is not settled. Not on man's role in causing the warming we've seen this century. Not on the consequences of this warming. Certainly not on the extent of warming -- or cooling-- to come.

The deniers I have written about are not just credible; they have reached the pinnacle of the scientific establishment, with credentials to rival those of any of scientists representing the IPCC position. Here's Russia's Habibullo Abdussamatov, head of the space research laboratory of the country's renowned Pulkovo Astronomical Observatory, a member of Russia's Academy of Science. Or Henk Tennekes, former director of research at the Royal Netherlands Meteorological Institute. Or Henrik Svensmark, director of the Centre for Sun-Climate Research at the Danish Space Research Institute. Or Edward Wegman, chair of the National Academy of Sciences' Committee on Applied and Theoretical Statistics.

Or, for a more direct comparison of scientists in the denier and the "science is settled" camps, consider Richard S. J. Tol, director of the Centre for Marine and Atmospheric Science at the Institute for Environmental Studies at Vrije Universiteit, or Christopher Landsea of the Atlantic Oceanographic & Meteorological Laboratory, or Richard Lindzen, professor of meteorology at the Massachusetts Institute of Technology and a member of the National Academy of Sciences. These three -- among the most cited scientists in the world in the field of climate change-- were universally acclaimed IPCC scientists until they disagreed with the positions espoused by the IPCC leadership. These deniers may no longer have an unqualified IPCC stamp of approval, but their academic credentials, record of scientific discoveries, and scientific prizes remain for all to see.