1) opposing views, conflicting arguments, debate.
3) Je n'ai pas vraiment compris la question ... a quoi doit - on relier ces phrases ?
4) Global warming is one the biggest problems knows nowadays, because nobody until now can predict what would exactelly happen in the futur and how big would be it's impact on us. However, even if all scientist agree on the fact that it's caused by human activity, their opinions about it are still devided.
Il pourrait y avoir quelques fautes d'orthographe et de grammaire mais bon j’espère t'avoir aidé.