When I add an appositive clause explaining subject that is different in term of singular/plural , how to choose verb agreement with the subject. Should I use " these chemical reactions" or " that is the greenhouse effect" as a subject or should I avoid all along by not adding appositive clause?

Some greenhouse gases such as carbon-monoxide or water vapor are natural gases which exist in the atmosphere already. Nevertheless, when we produce too much of the greenhouse gases, they trap the solar heat rays and prevent them from escaping from the Earth's atmosphere and surface. These chemical reactions, that is the greenhouse effect, results/ result in global warming.

Does the fact that these refers to the post-positioned the greenhouse effect affect the choice of tense?

  • 1
    Plural "result" is required since the expression that is the greenhouse effect is supplemental, an interpolation, as are most clauses introduced by that is (called an 'indicator'), and hence does not make the subject NP singular. Incidentally, the supplement is not an appositive; it's just an ascriptive NP supplement. It doesn't qualify as apposition because the supplement cannot be substituted for the whole construction in such a way as to yield an entailment of the original.
    – BillJ
    Jan 16, 2017 at 20:35
  • @Mrt, I'm going to edit your quoted statement to try and fix some distracting errors in order to concentrate on your question. I think there is an interesting issue buried in here. You can roll the edit back if you don't like what I did.
    – Phil Sweet
    Jan 17, 2017 at 3:09


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