There is his out. Pumping the oil TO refineries in Texas and Oklahoma does nothing to "exacerbate" but just having it refined and used does. He will do everything in his power to make sure it never gets there and instead to reward his benefactors in China who eventually will.
He wants the Chinese to gain profit from refining it and then transporting it all back here as just another means to take us down just one more notch. It has always been about damaging this country and has nothing to do with the environment. Case in point; It is just fin to be killing protected eagles and other winged creatures to advance his super expensive wind energy loser. All the while, the air in China is actually worse than all of the cartoons that the environmentalists want you to believe is happening here.
He will ultimately rely on the law of supply and demand. If the pipeline is built, more supply in the US for less money, enabling more demand to be met... - while if they have to ship it to China, even though ultimately it is burned there, he will justify keeping the prices higher in the US as a means to encourage conservation.