A double-pulsed, 2-μm Integrated Path Differential Absorption (IPDA) lidar instrument for atmospheric carbon dioxide (CO2) measurements is successfully developed at NASA Langley Research Center (LaRC). Based on direct detection technique, the instrument can be operated on ground or onboard a small aircraft. Key features of this compact, rugged and reliable IPDA lidar includes high transmitted laser energy, wavelength tuning, switching and locking, and sensitive detection. As a proof of concept, the IPDA ground and airborne CO2 measurement and validation will be presented. Ground validation of the IPDA lidar column CO2 measurements were conducted at NASA LaRC using hard targets and a calibrated in situ sensor. Airborne validation, conducted onboard the NASA B-200 aircraft, included CO2 plume detection from power stations incinerators, in-flight CO2 in situ sensor and air sampling at different altitude, conducted by NOAA at the same site. Airborne measurements, spanning for 20 hours, were obtained from different targets such as soil, vegetation, sand, snow and ocean. In addition, cloud slicing was examined over the ocean. These flight validations were conducted at different altitudes, up to 6 km, with different wavelength controlled weighing functions. CO2 measurement results agree with modeling results from different sensors.