One factor that plays into the amount of rainfall an area receives is the temperature of the seas from which the rain originates. Insufficient amounts of rainfall in a given area that is dependent on local agricultural production inevitably leads to crop failure, which leads to famine.

This fact can be seen throughout the Horn of Africa, where rainfall is currently scant and many people in the region are faced with the prospect of dealing with a drought and, inevitably, a huge famine. Scientists have pinpointed the cause of the insufficient rainfall to the warming of the Indian and west-central Pacific faster than other areas, causing more rain over the oceans and the descending of drier air over the Horn of Africa.