Rock climbing, in my limited experience, has had a profound effect on my grip strength, biceps, triceps, forearms, and core. But when I think about it, I firmly believe that this has to be the best back workout since you can have fun and test your mental capacity as well.
Basically, climbing is as close to a full body workout I have ever experienced. I get to train at a high quality gym with inverted walls, hundreds of bouldering problems, a bouldering cave, and plenty of tough climbs. But when you’re primarily pulling on the wall/holds, this puts a huge emphasis on the back. The motions put into rock climbing can lead to a developed and defined upper back.
Climbing is awesome and I highly recommend it. It is an excellent whole body workout, with the exception of chest, so you’ll want to supplement it with push ups etc. You have to take note however, that climbing will not get you to be massive. Most dedicated climbers have great bodies, but they are usually very lean, not massive and stacked. So it depends on what kind of body type you are after.
You put your eggs into one basket and go rock climbing if your goal is back development. You can come to the point that I don’t have to do any lifts specifically for your back. All you’re doing is pulling, so you’re going to see lots of development in your biceps and lats as well.