CO2 is a non-conductive gas so we are increasing our protection each day.
It didn't protect the earth between 10,000-2,000BC. If something like that happened again, virtually every electronic device and electric circuit would be completely fried. See the PDF at Scribd,
Characteristics-for-the-Occurrence-of-a-HighCurrent-ZPinch-Aurora-as-Recorded-in-Antiquity. Here is
another list of that and related material. You may have to find another way of downloading. I think I can because I'm doing it through my university that has library electronic journal privileges. Here is a
.gov site with these and other references that may be more generally accessible.