  Tropical Nevanlinna theory, introduced by Halburd and Southall as a tool to
analyze integrability of ultra-discrete equations, studies the growth and
complexity of continuous piecewise linear real functions. The purpose of this
paper is to extend tropical Nevanlinna theory to n-dimensional tropical
projective spaces by introducing a natural characteristic function for tropical
holomorphic curves, and by proving a tropical analogue of Cartan's second main
theorem. It is also shown that in the 1-dimensional case this result implies a
known tropical second main theorem due to Laine and Tohge.
