| Abbreviation | Definition |
|---|---|
| CIMMS | Cooperative Institute for Mesoscale Meteorological Studies |
| CIMRS | Cooperative Institute for Marine Resources Studies |
| CIMS | Chemical Ionization Mass Spectrometer |
| CIMSS | Cooperative Institute of Meteorology Satellite Studies |
| CINTEX | Catalogue Interoperability Experiment |
| CIPME | Committee on International Policy in the Marine Environment |
| CIRES | Cooperative Institute for Research in Environmental Sciences |
| CITE | Chemical Instrumentation Test and Evaluation |
| CITES | Convention on International Trade in Endangered Species of Wild Fauna and Flora |
| CLASS | cross-chain LORAN atmospheric sounding system |
| CLICOM | Climate Computing |
| CLIMAP | Climate, Long-range Investigation, Mapping and Prediction Study |
| CLIVAR | Climate Variability and Prediction |
| CLIVE | CoastaL Impacts Visualization Environment |
| CM | Current Meter |
| C-MAN | Coastal Marine Automated Network |
| CMC | Canadian Meteorological Centre |
| CME | Community Modeling Effort |
| CMG | Commission on Marine Geology |
| CMI | Caribbean Meteorological Institute |