The petition project is bunkum
a petition of scientists including such luminaries as Dr Michael J Fox, Geri Halliwell
Several environmental groups questioned dozens of the names: "Perry S. Mason" (the fictitious lawyer?), "Michael J. Fox" (the actor?), "Robert C. Byrd" (the senator?), "John C. Grisham" (the lawyer-author?). And then there's the Spice Girl, a k a. Geraldine Halliwell: The petition listed "Dr. Geri Halliwell" and "Dr. Halliwell.
.. If we remove all the engineers, medical professionals, computer scientists, and mathematicians, then the 31,478 “scientists” turn into 13,245 actual scientists, as opposed to scientists according to the OISM’s expansive definition..
..13,245 scientists is only 0.1% of the scientists graduated in the U.S. since the 1970-71 school year...
from skeptical science
A more recent survey of earth scientists asked the question "Do you think human activity is a significant contributing factor in changing mean global temperatures?". 97.5% of climatologists who were actively publishing papers on climate change responded yes.(Doran 2009). What is most interesting about this study was that as the level of active research and specialization in climate science increases, so does agreement that humans are significantly changing global temperatures.
Figure 1: Response to the survey question "Do you think human activity is a significant contributing factor in changing mean global temperatures?" (Doran 2009) General public data come from a 2008 Gallup poll.