Actually you are just not a comprehensive reader.
Article FULLY explains how this could cause an ice age.
Straight up.
You're extrapolating madly, to the point of confabulation. Ms. Smith provides little more than hand-waving. Here's the key passage:
The Earth's atmosphere would absorb the energy, which would separate nitrogen and oxygen molecules in the atmosphere, creating nitrogen oxides, including nitrogen dioxide, which plays a major role in the atmospheric reactions that produce ground-level ozone or smog.It is quite unclear what exactly produces the "global cooling." For instance, does the ozone depletion mentioned right in front of it figure in the chain of causation or is it just another effect? Even the wording is ambiguous. What exactly causes ambient temperatures to fall worldwide? Runaway albedo effect? Decreased greenhouse gasses? What?The scientists' research has led them to believe the long-term effects of gamma-ray bursts would deplete the ozone and cause global cooling and acid rain. It would also increase the amount of direct ultraviolet rays from the sun, which only reach a depth of 10 meters in water. This explains why only shallow marine species were involved in the extinction.