It's not a question of whether humans have any influence (I think you would be hard pressed to find any serious scientist who would hold that position) but of the balance between human and natural factors. The set of people who hold dissident beliefs is not tiny, and many of them are very serious people indeed. One can't dismiss them for saying many are not specialists in the official field of climatology because insights can come from many places (and there is the matter of playing games with the journals and people deliberately using political power to shut out dissident views).

Wiki isn't the best source on this topic, but here is one list, for example: https://en.m.wikipedia.org/wiki/List_of_scientists_opposing_...

The work that has been done relies heavily on models and simulations. These are both not realistic (because there are many factors that are too complex to model, or that we don't yet understand fully) and have not predicted temperature well since the outturn of past years has been significantly lower than predicted by the envelope of such models.

The political climate clearly is not one where people feel free to speak (see other stories on attempts or proposals to criminalise the expression of dissident views under certain circumstances or to create legal liabilities) and in that situation many people will keep quiet and hide what they really believe. See Timur Kuran's work on preference falsification.