The last decades have witnessed a tremendous explosion
in the use of topology in condensed matter physics, through the discovery
of exotic states of matter that are insulating in the bulk, but good
conductors at the edge of a sample.These materials support unidirectional
electronic edge waves that propagate without back-scattering in the
presence of impurities. These unidirectional waves are said to be topologically
protected, because they owe their existence to a topological invariant encoded
in the fluctuation spectrum of bulk electronic waves. This bulk invariant
guarantees the existence of unidirectional edge states when parameters are
varied, when boundary properties are changed, and when disorder is added.
Physicists realized recently that topological protection applies to virtually
all areas of physics from photonics, to cold atoms and even classical
mechanical systems. We will show that Eastward propagating heat waves involved
in El Niño phenomenon also have a topological origin. We will relate their
topological properties to the dual role of Coriolis force, that breaks
time-reversal symmetry, and changes sign at the equator thereby trapping waves
at the boundary between the two hemispheres.