Abstract Although the distribution of sunshine is symmetrical about the equator, the earth's climate is not. Climatic asymmetries are prominent in the eastern tropical Pacific and Atlantic Oceans where the regions of maximum sea surface temperature, convective cloud cover, and rainfall are north of the equator. This is the result of two sets of factors: interactions between the ocean and atmosphere that are capable of converting symmetry into asymmetry, and the geometries of the continents that determine in which longitudes the interactions are effective and in which hemisphere the warmest waters and the intertropical convergence zone are located. 'The Ocean-atmosphere interactions are most effective where the thermocline is shallow because the winds can readily affect sea surface temperatures in such regions. The thermocline happens to shoal in the eastern equatorial Pacific and Atlantic, but not in the eastern Indian Ocean, because easterly trade winds prevail over the tropical Atlantic and Pacific wher...