Fluorescence spectra and quantum yields of pyrene in supercritical CO2 are determined systematically as functions of temperature, CO2 density, and pyrene concentration. Under near-critical conditions, contributions of the pyrene excimer emission in observed fluorescence spectra are abnormally large. The results cannot be explained in the context of the classical photophysical mechanism well-established for pyrene in normal liquid solvents. It is thus demonstrated experimentally that the photophysical behavior of pyrene in a supercritical fluid is indeed unusual. The experimental results can be rationalized with a proposal that the local concentration of pyrene monomer in the vicinity of an excited pyrene molecule is higher than the bulk in a supercritical solvent environment. It is shown that the calculated ratios between the local and bulk concentrations deviate from unity more significantly under near-critical conditions. The implication of the proposed local solute concentration augmentation to the issue of solute-solute clustering in supercritical fluids is discussed.