But that doesn't make sense? The Paris agreement was NOT ratified by the Senate.
Exactly. See article [1], it lists all the weaknesses of the Paris agreement and why it was so weak. US, sorry, it's actually US' president, seems to act more and more selfish - it's almost humiliating to watch this as a European.
[1] https://theintercept.com/2017/06/01/will-trumps-slow-mo-walk...
It is important to know that the reason the Paris agreement is aspirational only is that it was necessary in order for the US to sign.
And the reason for that is the US political system. Any commitments would have had to be ratified by the US senate, which was deemed unlikely. Actual commitments had to be deferred to later agreements.
There is a whole string of climate agreements going all the way back to 1992, all building on another. (Therefore just pulling out of one of them isn't necessarily straightforward.)