I think you have misunderstood their position. They are the senior officers in their respective organisations. They represent the work of hundreds, thousands, of scientists
This.
And they should not be the ones making the decisions at a national policy level.
That is the job for people we elected. The problem is that the current government is utterly incompetent and actually doesn't really care.
And by the way, there seems to be wide misunderstanding of the ways that scientists work. Scientific data aren't ever absolutely in agreement - that is the point of proper science: researchers offer the best solution to explain the data as they exist.
But those explanations and deductions are always contingent, and open to interpretation (on a data-driven basis). It's a misunderstanding of scientific method that it aims to prove that something is right. Mostly scientists are working to see which theoretical model is the least wrong in accounting for the data (falsifiability).