  In this paper, we present the measurement of the energy spectra of carbon and
oxygen in cosmic rays based on observations with the Calorimetric Electron
Telescope (CALET) on the International Space Station from October 2015 to
October 2019. Analysis, including the detailed assessment of systematic
uncertainties, and results are reported. The energy spectra are measured in
kinetic energy per nucleon from 10 GeV$/n$ to 2.2 TeV$/n$ with an
all-calorimetric instrument with a total thickness corresponding to 1.3 nuclear
interaction length. The observed carbon and oxygen fluxes show a spectral index
change of $\sim$0.15 around 200 GeV$/n$ established with a significance
$>3\sigma$. They have the same energy dependence with a constant C/O flux ratio
$0.911\pm 0.006$ above 25 GeV$/n$. The spectral hardening is consistent with
that measured by AMS-02, but the absolute normalization of the flux is about
27% lower, though in agreement with observations from previous experiments
including the PAMELA spectrometer and the calorimetric balloon-borne experiment
CREAM.
