We consider the effects of volcanic activity upon zonal wind flow in a model atmosphere. A low latitude volcanic eruption could lower the tropospheric pole to equator temperature difference and thereby affect the atmospheric motions. When the temperature contrast decreases, the zonal wind velocities at high altitudes are reduced. To conserve angular momentum, the velocities in the lower atmosphere near the surface must increase, thus providing a momentum source for ocean currents. We suggest that this momentum source may have played a role as a trigger for inducing the 1982--83 anomalous El Nino and possibly other climate changes.