The magma pocket, which scientists have recently found to be 2.5 times larger than previously thought, measures 55 miles by 20 miles on each side and about 6 miles deep. That’s close to the size of the pocket when the supervolcano last erupted, 640,000 years ago...

If the supervolcano erupts, scientists predict that magma will spew more than 240 cubic miles from the eruption site, covering sections of Montana, Idaho and Wyoming. Global climate repercussions are also expected with ash and pulverized rock particles shooting into the atmosphere and drifting back down to Earth.

“You’ll get ashfall as far away as the Great Plains, and even farther east,” Farrell said.

...Any volcanic material that remains in the atmosphere will make it difficult for the sun’s rays to penetrate down to the ground. As a result, it’s predicted that temperatures across the world will decrease.

http://www.yellowstonepark.com/2014/01/super-volcano-twice-large/

    So is this the cure for global warming? :-)