If it doesn’t work, it doesn’t work. Back to the drawing board.

If it works, then let’s reproduce it a couple times to be sure that it works, and then start pouring concrete. Fusion isn’t worth pursuing just because of global warming, but because it’s akin to making energy out of nothing. We would have a nigh limitless capacity for conducting fusion and generating energy. A future with unlimited energy isn’t a climate goal necessarily, it’s a massive leap for humanity overall.