This paper presents a novel design of a 'Sensor on a Chip' spectrometer, based on silicon on silica (SOI) material. It employs a series of silicon micro-ring resonators with varied diameters whose resonance wavelengths evenly space out across the CO2 emission spectrum range. This provides a resonators-based detection platform for the observation of the Earth's atmospheric CO2 levels, as well as for the monitoring of the air quality related CO2 level and car exhauster CO2 pollution level. This chip-based spectrometer can collect light, propagate it along a bus waveguide, coupling the light into the ring resonators at their resonant wavelengths, and then drop off the light onto an output waveguide which is coupled with a broadband photodiode detector. The chip can be readily made by conventional silicon based semiconductor process technology.