Two years ago today, the sun spit out a storm powerful enough to shut down the Internet, GPS, satellites and more. Huge plasma clouds, known as coronal mass ejections (CME), made up what's thought to be the most powerful solar storm in 150 years.

As you probably know, the Internet never came to a screeching halt. But it nearly did, according to a University of Colorado researcher.

"I have come away from our recent studies more convinced than ever that Earth and its inhabitants were incredibly fortunate that the 2012 eruption happened when it did," Daniel Baker of the University of Colorado tells NASA .  "If the eruption had occurred only one week earlier, Earth would have been in the line of fire."

The last big solar storm, the Carrington Event of 1859, shut down telegraph lines. The damage today would be far worse, NASA explains:

A similar storm today could have a catastrophic effect. According to a study by the National Academy of Sciences, the total economic impact could exceed $2 trillion or 20 times greater than the costs of a Hurricane Katrina. Multi-ton transformers damaged by such a storm might take years to repair.

So, what makes our technology so sensitive? 

Extreme solar storms pose a threat to all forms of high-technology. They begin with an explosion--a "solar flare"—in the magnetic canopy of a sunspot. X-rays and extreme UV radiation reach Earth at light speed, ionizing the upper layers of our atmosphere; side-effects of this "solar EMP" include radio blackouts and GPS navigation errors. Minutes to hours later, the energetic particles arrive.  Moving only slightly slower than light itself, electrons and protons accelerated by the blast can electrify satellites and damage their electronics. Then come the CMEs, billion-ton clouds of magnetized plasma that take a day or more to cross the Sun-Earth divide.  Analysts believe that a direct hit by an extreme CME such as the one that missed Earth in July 2012 could cause widespread power blackouts, disabling everything that plugs into a wall socket. Most people wouldn't even be able to flush their toilet because urban water supplies largely rely on electric pumps. 

And while it didn't happen in 2012, it could happen in the near future. A recent journal article from "Space Weather" gives a 12 percent chance that another Carrington-class storm will hit earth in the next 10 years. 

"We need to be prepared," Baker told NASA.