"Due to the fact that the mailing list is more extensive than the discipline of climate science, a true random sampling technique was not employed.Rather, subjects were selected first according to institutional and disciplinary affiliations, all of which were related to the climate sciences. Nonetheless, the mailing list was adequate to provide the predetermined sample size of 500 North American scientists."
...Luntz suggested new White House phrasing on subjects like global warming (though "the scientific debate is closing against us," he wrote, minds could be eased by making "the lack of scientific certainty a primary issue"). He also laid out specific language designed to soothe voters. Some of it, such as the phrase "Safer, cleaner, and healthier," soon showed up verbatim in speeches by GOP policymakers.