We consider the wave equation (−∂ 2 t +∂ 2 ρ −V −VL(−∆ S 2 ))u = f F ′ (|u| 2 )u with (t, ρ, θ, φ) in R×R×S 2 . The wave equation on a spherically symmetric manifold with a single closed geodesic surface or on the exterior of the Schwarzschild manifold can be reduced to this form. Using a smoothed Morawetz estimate which does not require a spherical harmonic decomposition, we show that there is decay in L 2 loc for initial data in the energy class, even if the initial data is large. This requires certain conditions on the potentials V , VL and f . We show that a key condition on the weight in the smoothed Morawetz estimate can be reduced to an ODE condition, which is verified numerically.We consider the following defocusing wave equation:Our goal is to show that, under conditions 1-11 on the potentials (see below),if the initial data (u 0 , u 1 ) has finite (but possibly large) energy. In fact, we show the stronger result that. Equation (1) describes several interesting geometric wave equations. On a spherically-symmetric, 3-dimensional, warped-product of R and S 2 , Riemannian manifold, the metric is ds 2 = dρ 2 + r(ρ) 2 dω 2 , and if r has a unique minimum, it corresponds to a closed geodesic surface. This is the first problem we consider, and, by translation, we may assume that the closed geodesic surface occurs at ρ = 0. The semi-linear wave equation (−∂ 2 t + ∆ g )ũ = |ũ| p−1ũ can be reduced to (1) by setting u = rũ, in which case V = r ′′ /r,. The conditions 1-11 on the potentials are, therefore, conditions on r. These conditions are not vacuous, since, for example r = 1 + ρ 2 generates a wave equation which satisfies these conditions. Similarly the wave equation on the exterior region of the 3 + 1-dimensional, Schwarzschild manifold also can be reduced to (1) if p = 3, and this is the second case we consider. Both cases are explained in more detail in [2].The purpose of this note is to show that there is decay even for large data (defocusing) semi-linear problems. In [2], we considered the linear equation ((1) in which the right-hand side is absent) in both the Riemannian and Schwarzschild cases, and the non-linear problem with small initial data in the Riemannian case. In these cases, we were able to show that the space-time integral ũ L 4 (dtdρd 2 ω) is controlled by weighted H 1+ǫ norms. This built on previous work [3], in which the L ∞ norm was shown decay if weighted H 3 norms were bounded (and the initial data was small in the non-linear case). Similar results, with better decay estimates at the event horizon (an important part of the Schwarzschild manifold, corresponding to ρ → −∞) have also been proven [4].We make the following assumptions on the potentials and non-linear terms:1