"The goal is to inform the public, scientific community and media that the upcoming IPCC report doesn't have all the science to make informed judgments," said Jim Lakely, a spokesman for the Heartland Institute, a libertarian think tank based in Chicago that has been spearheading the efforts.
Heartland gained notoriety last year after running a billboard campaign comparing climate change believers to "Unabomber" Ted Kaczynski, which caused several corporate donors to withdraw support for the group.
The fifth assessment by the IPCC, the world's leading scientific advisory body on global warming, is expected to conclude with at least 95 percent certainty that human activities have caused most of earth's temperature rise since 1950, and will continue to do so in the future. That's up from a confidence level of 90 percent in 2007, the year the last assessment came out. The IPCC, which consists of thousands of scientists and reviewers from more than 100 countries, shared the Nobel Peace Prize with Vice President Al Gore. Governments often use its periodic reviews of climate risks to set targets for reducing carbon emissions and other policies.