Climate change sceptic Wei-Hock 'Willie' Soon received funding from the energy industry amounting to more than $1.5m (£976,000) since 2001.

The Harvard-Smithsonian Center for Astrophysics (CfA) has now launched an investigation into Soon, a solar physicist, following the release of a Freedom of Information Act request obtained by Greenpeace that shows research contracts and commitments made by Soon to corporate funders.

CfA is looking at whether Soon reported the funding in the right manner – while there is no explicit policy on disclosing funding sources, authors are expected to announce any potential conflicts of interest.

The funding Soon is accused of receiving from the fossil fuel industry included $400,000 from the energy firm Southern Company and $200,000 from the Charles G. Koch Charitable Foundation, an organisation tied to the oil industry.

The report suggests that in at least eight papers since 2008, his failure to disclose the funding source would violate the ethical guidelines of the journals publishing his work.

Soon is known as a vehement climate sceptic, linking climate change to the sun rather than human activity. For example, in 2009, he said: "The evidence in my paper is consistent with the hypothesis that the Sun causes climatic change in the Arctic.

"It invalidates the hypothesis that CO2 is a major cause of observed climate change – and raises serious questions about the wisdom of imposing cap-and-trade or other policies that would cripple energy production and economic activity, in the name of 'preventing catastrophic climate change'."

He is yet to comment on the allegations.

However, in an interview with The State News in 2013, Soon said he has not received funding from the US government since 2004 and that he would take money from anyone, including the oil industry, because he is not biased in his work.

"I've been trying to get funding from whoever, you know, foundation – anybody wants to give me money. Coal, anything, I don't care. Really, I don't because I know that I'm not being influenced by money."

Charles Alcock, director of the CfA, said they want to get the "facts straight" and that if there is evidence Soon failed to disclose "we have a problem".