There are two verbs: pouvoir and causer. Each has its own tense, which might be a compound tense involving the auxiliary avoir (with some verbs, it would be être instead). “Pouvoir causer” as a whole doesn't have a tense.
- pourrait: conditionnel présent
- aurait pu: conditionnel passé
- causer: infinitif présent
- avoir causé: infinitif passé
Both sentences are correct. They have different meanings.
Cet événement climatique pourrait causer de graves conséquences.
The event is happening now, or this is a discourse about the event in the present tense. It is not known whether the event will have grave consequences, but it is a possibility. The conditional makes it a hypothetical of the not-known variety: we don't have enough knowledge to decide whether grave consequences will result. The distinction between “pourrait causer” and
“peut causer” (indicatif présent) is similar to the distinction between “can cause” and “could cause” in English.
Cet événement climatique pourrait avoir causé de graves conséquences.
The event happened in the past. Whether it has had grave consequences is not known yet. There are no known grave consequences, but bad things may have already been triggered. If bad things have been triggered, we haven't found out yet, or we know about these things but we don't know that the event in question caused them.
Cet événement climatique aurait pu causer de graves conséquences.
The event happened in the past. Events of this nature are known to have a possibility of causing grave consequences. However, we know that this particular event did not have grave consequences. Here the conditional is a hypothetical of the what-if variety: if the event had turned out differently, it could have been bad, but in this particular case it didn't turn out to be bad.