An embodiment of a system for measuring trace gas concentration is described that comprises a laser absorption spectrometer configured to detect an absorbance measure from a trace gas, as well as a temperature value and a pressure value that correspond to an environment in a gas cell; and a computer having executable code stored thereon configured to perform a method comprising: receiving the absorbance value, the temperature value, and the pressure value; defining a fitting range associated with the trace gas; applying a curve fitting model in the fitting range to the absorbance value using the temperature value and the pressure value as model parameters; and producing a concentration measure of the trace gas.