[keiferski]

That's not how science works. "Have been found" is not a weasel phrase, it's an accurate description of empirical observations.

[kd5bjo]

It is a weasel phrase: It gets you out of citing your source for the information, which deprives the reader of judging its accuracy for themselves. I'd probably write it this way:

"Jones (2018) showed that regular patterns of drought and precipitation coincide with cycles of sunspot activity."

[BigJ1211]

It also implies you weren't the one to find it and are you relaying that information to the reader.