The PhD program of the Max Planck Institute for Meteorology, Hamburg, is looking for new PhD students. Topics will be officially be decided during/after the interviews. The institute has a strong focus on earth system modeling. I’d recommend talking with potential supervisors before applying. Application deadline is September, 15. Start of the PhD would be in 2020. The semester fee mentioned in the pdf currently is about 650 Euros per year (includes local public transport).
Details at http://imprs-esm.mpimet.mpg.de