Oh, it’s looking for a size function. It’s working, but it can’t display since it think it’s a vector so it’s trying to use the full vector interface.
http://docs.julialang.org/en/stable/manual/interfaces/#abstract-arrays
That page explains the full interface. You just define a few methods (size, etc.), and the functions which work on AbstractArrays will now work on your ClimateVector, like giving it a nice show method.