Answer
weeks
days
centuries
decades
To see statistically significant warming, the planetary imbalance must persist for decades.
Imbalance? It doesn't define how much of an imbalance.
Significant? Significant to whom?
It isn't a very good scientific question so you have to analyze its political intent.
Since weeks or days can be eliminated, you have to wonder if it is decades or centuries. Since centuries is too long to push a political agenda, your answer is probably decades.
Decades.
Another gobble-de-**** question from a communist agitator.
A planetary imbalance must persist for ________________ before we see significant warming.
Answer
weeks
days
centuries
decades