Considerable quantities of carbon dioxide (CO (sub 2) ) gas recovered from power plants, ethanol manufacturing, and coal gasification facilities are proposed to be injected underground into deep subsurface reservoirs. Effective geological sequestration requires monitoring to ensure that any leakage can be recognized. In the Midwest, particularly Illinois, surface land use above large areas of potential sequestration reservoirs consists of corn-soybeans crop rotation. A multidisciplinary program tested whether a simulated large leak from a reservoir could be detected within rowcrops by aerial thermal infrared imagery. Carbon dioxide gas was released in a monotypic soybean field beneath the plant canopy at the rate of 300-450 standard cubic feet per hour (SCFH) simulating point sources (sprinklers) and a fracture (6-foot perforated pipe). As expected, response to higher-than-ambient concentrations of CO (sub 2) decreased stomatal conductance resulting in an increase of canopy temperatures (up to 5 degrees C) measured by ground-based thermal infrared imagery. Aerial thermal infrared (TIR) imagery acquired late in the growing season was obtained with a 3.5-5.5 micrometer FLIR 8500FW instrument mounted on a helicopter. Imagery shows the CO (sub 2) -affected soybeans had noticeably greater thermal exitance (warmer) than nearby plants after a 6-hour exposure. Guided by an air-to-ground imagery transmitter, ground measurements of atmospheric CO (sub 2) concentrations at three heights (ground, underside of canopy and midway) as high as 1.8sub 2) escapes within soybean fields.