‘Increase,’ when combined with other ‘contemporaneous increases and decreases’ must result in an aggregate increase.

“(2) The term ‘increase’ includes the emission of a significant amount of any air pollutant which was not emitted before the physical change referred to in paragraph (1). The terms ‘significant net increase’ and ‘significant amount’ shall have such meaning as provided in regulations of the Administrator. Such regulations shall include within the meaning of such terms any increase in emission of an air pollutant (or new emissions of the pollutant) which, when combined with other generally contemporaneous increases and decreases in emissions (or new emissions) of that pollutant, result in an aggregate increase in emissions of that air pollutant in excess of a de minimus amount determined by the Administrator by rule.