Young grizzly bears can climb trees as well as black bears, but adult grizzlies are challenged. Shorter claws are ideal for a bear climbing trees, which is the case for black bears and young grizzlies. Adult grizzlies having bigger claws and more weight struggle climbing trees and are more likely to pull them self up, using limbs of the trees. In the case of this picture, one cub is part way up the tree and the other is thinking about it, after being startled by loud sound.
Until next moment,
Amar