The BBC must have a clerk stashed away in a dusty basement somewhere with a green eyeshade and a calculator to figure out these inane volumetric comparisons. No doubt they do that in the US as well. Let's see... That's enough spaghetti sauce to fill, er, "one hundred Madison Square Gardens all the way from the hockey rink surface to the cheap seats". Uh, no, how about, "to fill Lake Pontchartrain' - oh, that's too large, and it's in flyover country, it won't mean a thing to the average New York Times reader. OK, how about "to cover Central Park to a depth of (calculate... calculate... calculate...) eight inches"? Yeah, that'll really make it clear to the readers, eveybody can relate to having eight inches of spaghetti sauce covering Central Park...
Now you are gonna upset all the Italians who would see it as a waste of perfectly good spaghetti sauce....I like the stuff too...LOL!
I didn't think 2.5 cubic Km sounded like that much until I realized it would be a kilometer high.