clipping kitten claws

I have a 5 week old kitten and I was wondering when to start trimming his nails, and how much effect it would have on his climbing abilities.

He does not scratch intentionally, but his claws are very sharp and at his young age he doesn't have the best control over them. He loves to climb and I don't want to hinder him in any way, but those nails are like razors!

Welcome to The Cat Site.
I would first just pet his paws, kind of play with his fingers/claws. That way you can maybe determine how sensitive your cat's paws are. I know of one cat who had no problem with me cutting his nails, but Ritz hates it, and I only do it when she is asleep.
Once you get an idea how sensitive they are which in turn will help you how many nails at a time can you clip before Kitty grows impatient!, then go ahead and try clipping one or two nails and proceed, or not, accordingly. Have treats nearby so every time you clip a claw Kitty gets a treat/reward.
And no trimming nails won't hinder his ability to climb; for one reason, cats use muscles in their legs and shoulders to climb.
Good luck!

With tiny kittens, it is often easier to use the small human nail clippers rather than cat claw scissors and just take off those razor-like points.  You don't have to cut them short, and always cut only in the clear area.  When we raise kittens, we start cutting their claws when they are only around 3 weeks old because it saves wear and tear on the mama cats (or us, if we are bottle feeding orphans).  It's best that tiny kittens can't get stuck in things also, so claw clipping helps with that.

Thank you both so much for the help!