Actually there can be. It's called technique. My power to weight ratio did not change but my climbing got better because of two things I learned from others. First, I learned to exhale with force which emptied my lungs allowing me to inhale more air. That helped me a lot. Then a professional trainer explained that some people can climb better with increased rpms while others can use bigger gears and rely on power. It depends on your body type and strength. I abandoned the former for the latter and my climbing improved again. So, it doesn't have to be just power to weight.