Translation:In the South it is warm, and in the North it is cold.
I had the same "error' -- and this after having just read in the previous lesson's notes that i and not a should be used for complete sentences. I admit I am not clear on the Russian, but it is very irritating to not be able to use appropriate English (explained by one user as having to do with the programming of R-E with E-R).
No, it's unrelated. The word «север» is the original Russian word, the word «Сибирь» 'Siberia' is a loanword, it was borrowed from the people who lived in Siberia.
The suggested translation uses «на юге» = 'in the South', and «на севере» = 'in the North'. Север and юг are the usual Russian words for 'South' and 'North'.