No, do not prune back your young climbing rose. The plant is building a frame for future blooms and you will most likely see more flowers next summer. The main canes or branches should be allowed to grow tall and trained over an arch or curved into a fan shape. This bending of the tips of the new growth will encourage side shoots to emerge from these main stems. It is the side shoots that bear the blooms usually after a summer or two of growth. In future years you can prune back the side shoots by one third but don't prune back the entire climbing rose. I can almost promise you a better rose garden next summer if you fertilize in the spring and summer and keep the soil moist during droughts. Keep growing, Marianne Binetti