In case nobody noticed, former TX gov. Rick Perry did speak out on this, and he was in favor of the Paris accord, also.
Shocking that Trump would go against the current head of Exxon, the ex-head of Exxon who is also his Sec. of State, and another very conservative oil-state politician in Rick Perry.
I believe Tillerson wanted to stay in Paris so the United States would be involved in the program and shape it's direction. I'd say that's quite a bit different than voluntarily taking on the pledges for Texas.