There are different grades of aluminum such as 4043. or1100 which 1100 is a little harder to weld but if I can do it anyone can, Lol. Just make sure you do the research on the material that you are using. I personally have welded plenty of pipe in the 4043 type which is very strong. And you can use either Tig, or Mig for your application, they also make a regular aluminum welding rod but good luck in running it, for it is truly different. I hope this helps, but as one welder to another you always have to watch both sides to make sure that you are actually bonding, & not simply laying medal over another.
Another thing to think of is research what type of material they use on the aluminum climbers, just food for thought.