How the HELL would you measure something like that?
It's really simple.
Step 1: Take a measurement of the sea level.
Step 2: Take a measurement of the sea level after Michael Moore has jumped in the ocean.
Step 3: "Oh n0es! Global warming has caused the sea level to rise three feet in the past two days! We're doooooooooomed!
Step 4: Blame Bush, Rove, Palin, the JOOOOOOS, Bush again, and Cheney