Because climate is part of the global system, clearly one must understand the interaction of all the components.
Which means the Climate Whiz (et al) know what all the components are.
And naturally, the Climate Whiz (et al) know what all the components do and how they work.
And, of course, how all the components interact.
With such knowledge one supposes that what 'they' say is true, there is nothing left to discover.
Oh, hey look here, was this already known? Hope there's nothing else hidden out there. How catastrophic could that be