Systems and methods described herein include improved data gathering, climate modeling and weather forecasting techniques. In particular, the systems include using Global Positioning System (GPS) measurements obtained from a network of GPS devices for simultaneously determining atmospheric parameters such as water vapor content, temperature and pressure, and correcting for errors in the GPS measurements, themselves. The systems and methods described herein include a central processor for receiving data from a plurality of GPS devices and updating a computerized climate or weather forecasting model. Advantageously, by using data from a plurality, and in some embodiments a very large number of GPS devices, the systems and methods described herein may solve for both propagation velocity of electromagnetic signals through the atmosphere (used for calculating atmospheric parameters useful in climate modeling) and GPS position error values (used for error correction at each GPS device).