Just build a skyscraper with around 40,000 cu metres of concrete = 80,000 tonnes - each tonne equivalent to one tonne CO2 emissions. That's bad.
But this is the really clever bit, mandate some greenery and trees. That should do the trick. In this case about 20 small trees, perhaps weighing half a tonne = 10 tonnes C or 34 tonnes CO2 equivalent. That's good.
80,000 - 34 = 79,966 tonnes CO2 emitted in the construction of the tower, no calculation given or attempted as the CO2 emitted powering this building or keeping it cool, which of course will be massive as the building is faced with glass (to be banned in New York). That's mad.
And some people remain optimistic we'll deal to global warming??