It's impractical to demand both domain expertise and total impartiality - even academic researchers have strong proclivities. There are no neutral parties, and this is clearly labeled as one person's opinion.
Granting the premise that there are no absolutely neutral parties, we can still agree that there are parties which are less neutral than others. Having a direct financial interest is a pretty hard line: for example, if the author was heavily invested in geoengineering companies, or had even been paid by geoengineering companies to write the article, I hope everyone would agree that his opinion was suspect. In this case, the author does not have a direct financial interest, but he has (I suppose) an indirect one, which is why I say I appreciate the article, but would prefer the same argument from coming another source, if I had the choice.
