| C | Centigrade | - | Scuba Diving |
| CAC | Climate Analysis Center | - | Scuba Diving |
| CCR | Center For Climatic Research (IES) | - | Scuba Diving |
| CD-ROM | Compact Disc-Read Only Memory | - | Scuba Diving |
| CERES | Clouds And The Earth's Radiant Energy System (EOS) | - | Scuba Diving |
| CFC | ChloroFluoroCarbon | - | Scuba Diving |
| CH4 | Methane | - | Scuba Diving |
| CIMSS | Cooperative Institute For Meteorological Satellite Studies | - | Scuba Diving |
| COMET | Cooperative Program For Operational Meteorology Education And Training (NOAA And UCAR) | - | Scuba Diving |
| COMSAT | COMmunications SATellite | - | Scuba Diving |
| CONUS | CONtinental (or CONterminus) United States | - | Scuba Diving |
| CPC | Climate Prediction Center (NWS Center) | - | Scuba Diving |
| CRAS | CIMSS Regional Assimilation System | - | Scuba Diving |
| CRIS | Cross-track Infrared Sounder | - | Scuba Diving |
| CSBT | Clear-Sky Brightness Temperature | - | Scuba Diving |
