Drought is a condition, not a hypothesis. Drought is the lack of rain, or evaporation in excess of precipitation.
The CAUSE of drought is a multi-pronged hypothesis. It can be due to cyclic changes in ocean temperature (El Niño/La Niña). It can be due to rain shadow downwind of a mountain range. It can be due to fluctuations in the sun’s brightness. It can be the result of urban sprawl and resulting shifts in upwind evaporation/transpiration. It can be the result of climate bands shifting in response to changing atmospheric composition. It can be the result of agricultural practices upwind. It can be just bad luck, with a location consistently not being the whatever-percent chance of where it’s raining.
These changes in air pressure and wind speed cause<span> warm surface water to move eastward along the Equator, from the western Pacific to the coast of northern </span>South America<span>. </span>
