I have always thought it would be incredibly easy for terrorists to shutdown oil pipelines if they tried. 1000's of km of completely isolated unguarded pipeline. But Sabotage would be devastating to the local environment, even if it would save the global one long term.
It doesn't have to be environmentally damaging. Years ago there was a group called "valve turners" who just closed emergency shut off valves all over the place.
I agree but I also wouldn't call something like that terrorism either. Turning a valve can be reversed in seconds, some sort of destructive sabotage could take months to repair.
Now we've gone from seconds to fix to hours to fix. If you wanted better I'd say to target pumping stations. If you could cause some serious damage to the pumps that push the oil, you could take the entire line out of commission for a good long while.
Of course, the pumping stations are guarded, and it isn't a good look for ecoterrorists to kill people. But maybe you could pull a Stuxnet.