For years, politicians wanting to block legislation on climate change have bolstered their arguments by pointing to the work of a handful of scientists who claim that greenhouse gases pose little risk to humanity.

One of the names they invoke most often is Wei-Hock Soon, a scientist at the Harvard-Smithsonian Center for Astrophysics who claims that variations in the sun’s energy can largely explain recent global warming. He has often appeared on conservative news programs, testified before Congress and in state capitols, and starred at conferences of people who deny global warming’s risks.

But newly released documents show the extent to which Soon’s work has been tied to funding he received from corporate interests.

He has accepted more than $1.2 million in money from the fossil-fuel industry over the last decade while failing to disclose that conflict of interest in most of his scientific papers. At least 11 papers he has published since 2008 omitted such a disclosure, and in at least eight of those cases he appears to have violated ethical guidelines of the journals.

The documents show that Soon, in correspondence with corporate funders, described many of his scientific papers as “deliverables” that he completed in exchange for their money. He used the same term to describe testimony he prepared for Congress.

Though Soon did not respond to questions about the documents, he has long stated that his funding has not influenced his scientific findings.

The documents were obtained by Greenpeace under the Freedom of Information Act. They shed light on the role of scientists like Soon in fostering public debate over whether human activity is causing global warming. The vast majority of experts have concluded that it is and that greenhouse emissions pose long-term risks to civilization.

Historians and sociologists of science say that since the tobacco wars of the 1960s, corporations trying to block legislation that hurts their interests have employed a strategy of creating the appearance of scientific doubt, usually with the help of ostensibly independent researchers who accept industry funding.

Fossil-fuel interests have followed this approach for years, but the mechanics of their activities have remained largely hidden.

“The whole doubt-mongering strategy relies on creating the impression of scientific debate,” said Naomi Oreskes, a science historian at Harvard University. “Soon is playing a role in … political theater.”

Environmentalists have long questioned Soon’s work, and his acceptance of funding from the fossil-fuel industry was previously known. The full extent of the links was not; the documents show that corporate funds were tied to specific papers and not disclosed.

“What it shows is the continuation of a long-term campaign by specific fossil-fuel companies and interests to undermine the scientific consensus on climate change,” said Kert Davies of the Climate Investigations Center.

Charles Alcock, director of the Harvard-Smithsonian Center, acknowledged that Soon had violated some disclosure standards.

“That’s inappropriate behavior,” Alcock said. “This frankly becomes a personnel matter, which we have to handle with Dr. Soon internally.” Soon is employed by the Smithsonian Institution, which sponsors the astrophysics center with Harvard.

“I am aware of the situation with Willie Soon, and I’m very concerned about it,” said W. John Kress, interim undersecretary for science at the Smithsonian. “We are checking into this ourselves.”