19 million Amps
deblau writes "On July 27, scientists at the National Nuclear Security Administration's Nevada Test Site said they generated a current equal to about four times all the electrical current on Earth. During the few millionths of a second that it operated, the 650-ton Atlas pulsed-power generator discharged about 19 million amps of current through an aluminum cylindrical shell about the size of a tuna can. Official news release is available from the DOE (PDF)."
(12x10^6)^2*(.781x10-9) = 112.464kW.
That's not much power. In addition, it only lasted a few milliseconds so it wouldn't come close to the total power usage of the world in a year.
I've seen 1/1000th of this current used on a daily basis through 14 guage wire as part of the wire making process. When I worked on wire drawing and annealing machines, I measured a constant 1900 amps on the wire at about 2000 feet per second. The voltage drop was about 30 volts for about 15 feet. The magnetic field was pretty strong and the wire got hot enough to soften it. If the wire were stationary, it would take about a second or two to melt it. If I were to take 10,000 strands of that 14 guage copper wire (which is much more conductive than aluminum) we'd have about 19 million amps, but I'm sure the magnetic field would have presented interesting challenges.
Per this news release here this has already been done by the mentioned generator. They even use the tuna can size reference;
"In the shot, the 650-ton Atlas pulsed-power generator successfully discharged approximately 20 million amperes of current through an aluminum cylindrical shell or liner about the size and shape of a tuna can, causing the liner to implode at very high speeds. "
With this much current I think of the rail gun technology. Will this lead to a rail gun that is powerful enough to accelerate a chunk of metal to escape velocity. That is could we place a robotic factory in orbit around the earth and produce a gigantic mirror that could reflect light away from the path of a hurricane and use that light to generate huge amounts of power that could be microwaved back to earth.