Factor of climate change disseminated on-line (2,4)
I believe the answer is:
el nino
'factor of climate change' is the definition.
(El Nino is a climate pattern)
'disseminated on-line' is the wordplay.
'disseminated' indicates anagramming the letters.
'on line' becomes 'on-line' (synonyms).
'online' is an anagram of 'EL NINO'.
(Other definitions for el nino that I've seen before include "Warm sea-current" , "Periodical Pacific weather phenomenon" , "Pacific climate pattern" , "Pacific weather feature" , "system of current activity" .)