Controlled environment chambers (e.g. growth chambers, SPAR chambers , or open-top chambers) are useful when the data collected in them illustrates how plant ecosystems will actually respond to changes in climate, that is, they do not alter the direction and/or magnitude of the response. However, obtaining data that is not confounded by numerous artifacts (e.g.  side-lighting, edge effects, increased temperature and vpd, etc) is difficult and this limits what can be measured accurately. A great deal of rigor and understanding must be used in order to study ecological processes affected by climate change in controlled environments, in part because controlled environment chambers are much more turbulent than field situations. The measurement of canopy stomatal conductance and its response to CO₂ concentration is discussed. Chambers can be used to measure canopy level energy balance under controlled conditions and plant transpiration responses to CO₂ concentration can be elucidated. However, these measurements cannot be used directly as if they would occur in a natural setting. The response of stomatal conductance to CO₂ will be the same as in the field, but the measured response must be recalculated in such a manner to account for differences in aerodynamic conductance, temperature and vpd between the chamber and the field.