The pervading mood all round the world (10)

I believe the answer is:

atmosphere

I'm a little stuck... Click here to teach me more about this clue!

'the pervading mood' is the definition.
(I've seen this before)

'all round the world' is the wordplay.
'all round' becomes 'atmo' (I can't justify this - if you can you should believe this answer much more).
'the world' becomes 'sphere' (I've seen this in another clue).
'atmo'+'sphere'='ATMOSPHERE'

Can you help me to learn more?

(Other definitions for atmosphere that I've seen before include "Air" , "Feeling" , "prevailing mood" , "blue?" , "Feel" .)

I've seen this clue in The Guardian, The Globe and Mail and The Telegraph.

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