[sharkjacobs]

Engaging with the existing literature would be a good start.

If you were interested in studying the relationship between bias and funding you might do a survey of published papers and articles on the subject.

If you can identify some measurable criteria that can be used to rate how "green" a paper's funding is then you can use that as an axis and compare the surveyed papers to reveal trends.

[butterNaN]

Additionally, since one is already doing that, check out what kind of funding Fossil Fuel companies have done in the past and present.