Manager Phil Parkinson made his move after regular number one Rob Elliot was ruled out for a month with a groin injury.
"We needed to get a goalie because you can't go into the last nine games with only one senior goalkeeper," said Parkinson.
Warner will challenge Darren Randolph for the gloves when the Addicks travel to promotion rivals Huddersfield on Saturday.
Source: Team Talk
Source: Team Talk