A 'World Authoritarian Government' wouldn't last long if it were actually possible to get every nation on board, but I expect North America, Western Europe and their allies will attempt to pull something like this off in a last ditch attempt to regain control of their own failing countries and their global interests before they collapse and break up into smaller independent nations or get swallowed up by rival powers, with the inevitable conflict, death, poverty and misery that process will entail.
It won't happen all at once. Most of us will be able to see out our day to day lives and adjust accordingly as things become steadily worse over time. A percentage of the population will always thrive and do well out of a crisis, however small.
All of this is of course assuming it won't go thermo-nuclear, which cannot be ruled out. Accidents/errors are more likely to occur when tensions are raised.