Cho Oyu is a recurrent problem peak as it is a small hump about 30 mins into the summit plateau, and the main proxy of a view of Everest, which is possible from the true summit, requires clear weather. Shishapangma is another problem peak because of its dual summits, which despite being close in height, are up to two hours climbing time apart. Hawley judged that Ed Viesturs had not reached the true summit, and he re-climbed the mountain to definitively establish his ascent.