We quantify the temperature dependency of the VUV absorption cross section of carbon dioxide. The VUV absorption cross section of CO_2_ increases with the temperature. The absorption we measured at 150K seems to be close to the absorption of CO_2_ in the fundamental ground state. The absorption cross section can be separated in two parts: a continuum and a fine structure superimposed on the continuum. The variation of the continuum of absorption can be represented by the sum of three gaussian functions. We used these data in our 1D thermo-photochemical model in order to study their impact on the predicted atmospheric composition of warm exoplanets. Using data at high temperature in thermo-photochemical models modifies significantly the abundance and the photodissociation rates of many species, in addition to carbon dioxide, such as methane and ammonia. These deviations have an impact on synthetic transmission spectra, leading to variations of up to 5ppm.