The single most important strength in ice climbing is the ability to hang onto your ice tools. Getting pumped while ice climbing is sketchy because if your forearms get pumped you can't swing effectively at best, and at worst you'll fall off if your feet blow. So, get stronger. Tabata hangs are just 20 seconds of hanging followed by ten seconds of rest, done for eight reps. I find four sets of these are about all that I can handle. If I could only do one ice climbing specific exercise it would Tabata hangs.
You can reduce load by keeping your feet on the ground in front of you, or add rubber bands if you want to get fancy. Increase load by doing them one-handed in a figure four or nine. Note that hanging one-handed for an entire Tabata set will likely mess you up unless you're psycho strong, so I like to do them in a figure four or nine to save my shoulder.
You can do these on your normal ice tools too, but the Furnace tools are a bit harder to hang onto, and you can use them in your normal weight room without freaking people out like ice tools would. In fact, this exercise is the single most important training exercise to do in any weight room. Add in some pullups during the hangs, front lever progressions, but the emphasis is always on developing the ability to hang on for longer periods of time.
You will have reached "Gecko Mode" when you can hang onto your ice tools for
