Usage and Grammar
Q. Doesn’t “The US is the second-largest carbon dioxide emitter after China” make it sound like the US is actually the third-largest carbon dioxide emitter? I see these formulations, which include [number] plus [superlative] and a direct comparison, often, and they seem confusing. Wouldn’t it make more sense to say “The US is the largest carbon dioxide emitter after China” or “The US is the second-largest carbon dioxide emitter; China is the largest”?
A. You’re right: if you think about it for more than three or four seconds, that sentence is less than perfectly unambiguous. But no one would describe the third-largest emitter as the second-largest emitter after the second-largest emitter! This is an example of a convenient and harmless shorthand—where “after” means something like “trailing only.” And it’s a helpful shorthand: not only is it concise, but it also prevents the momentary ambiguity inherent in your first solution (“The US is the largest carbon dioxide emitter . . .”). Note that a comma, though typically omitted from “nth-largest . . . after . . .” constructions, would provide useful clarification before the prepositional phrase “after China”; before the participial phrase “trailing only China,” such a comma would be required (see CMOS 6.30).