A sting operation by the environmental group Greenpeace suggests that some researchers who dispute mainstream scientific conclusions on climate change are willing to conceal the sources of payment for their research, even if the money is purported to come from overseas corporations producing oil, gas and coal.

Over a period of several months, two Greenpeace employees posed as representatives of energy companies and offered to pay prominent commentators on climate change to write papers that extolled the benefits of coal and carbon emissions. The Greenpeace workers also asked that the payments not be disclosed.

The commentators — a professor from Princeton University and one from Pennsylvania State University — agreed to the offers.

Disclosure of funding for scientific research has been a flash point in the fight over climate change, especially in the case of published scientific research. The effort by Greenpeace, which has a long record of using aggressive tactics to make environmental statements, was to “unravel the story” of industry ties to denial of climate change, said Lawrence Carter, one of the Greenpeace employees involved in the subterfuge.