Understanding the sources and sinks of carbon dioxide and other greenhouse gases has been recognized as critical to predicting climate change and global warming. A variety of research studies funded by DOE, NSF, NASA and NOAA to measure the fluxes and fluctuations of CO2 profiles throughout the troposphere and lower stratosphere have provided a great deal of useful information, but the instrumentation used has been restricted to airplane or large stratospheric-type balloon gondola platforms where a few measurements are very expensive. We propose a new approach where low cost, extensive measurement campaigns can be made using standard meteorological balloons. In this SBIR program, Southwest Sciences is developing a lightweight, inexpensive greenhouse gas sensor suitable for balloon sonde measurements, Using a novel measurement technique, this sensor will provide dry air mixing ratios of CO2 without the need for concurrent measurements of temperature, pressure or moisture. The Phase 1 research successfully demonstrated the viability of this approach and in Phase 2, a prototype sensor will be built and field tested in a series of balloon-sonde flights.