The Glasgow skipper made a big impact in his first season at the Warriors after leaving Ednburgh.
Al told The Times: "You have a look round to see what is going on but to be honest there was never any real doubt that I would sign. It was a rugby decision. Glasgow are looking good, have signed really well and will continue to improve over the next couple of years. I want to be part of that."
Al was a surprise omission from the World Cup squad but said he is now over the disappointment and wants to lead Glasgow Warriors to as high a league position as possible.
"We are in a stronger position than we were last year. I feel I can improve as a player at Glasgow and that the team can improve as well," he said at the launch of the new Magners League season, held in the Swansea home of the Ospreys. "We have not set ourselves any targets. We have to improve on last year but we will sit down after the World Cup and assess where we are, then do the same at Christmas, and continue with that. As long as we are getting better, that is important."