I imagine it's the sentence "Some modelling studies have projected a decrease in the number of tropical cyclones globally...", which represents a decrease in on

I imagine it's the sentence "Some modelling studies have projected a decrease in the number of tropical cyclones globally...", which represents a decrease in one particular (important) kind of extreme weather event, although it says that in this case the tropical cyclones that do occur could be more intense. However, that might be the only kind of extreme weather event that the linked document mentions might become rarer; it also mentions other kinds of events for which it only mentions increased likelihoods, not decreased likelihoods.