Everyone could have a zero carbon footprint right now, and it wouldn't matter.   The abrupt change would continue, as would the storms, the melting ice, the forest fires, and the mass die-offs.   Geologic records indicate that the earth reaches tipping points.   Once a tipping point is reached, the changes occur very quickly and cannot be altered.   The same records also indicate that the earth has warmed as much as 6C to 8C in as few as 13 years in the distant past.   

What is occurring now is taking place with only about a 1C degree rise in global temperatures.  We will see 2C in the very near future.  Projections are at least 4C+ by 2100, but maybe much sooner than that, maybe even within a few years.  

This is going to get much, much worse.