This is a chart of Earth's magnetic field strength over the last 18,000 years.
I assume folks here know how to read a chart...
Earth's magnetic field strength may not be as weak as it was during the Younger Dryas catastrophe, but the rate of collapse is greater.
This tells us 2 things. The first being that Graham Hancock is full of shit. The root cause of the Younger Dryas event was no extraterrestrial impact, although it may very well have a role to play.
Something much bigger is at play.