This paper presents a method of reconstructing transient, three-dimensional axisymmetric temperature fields in water formed by laminar free convection from a small heating sphere. This method is based on the temperature dependence of the water absorption coefficient at a near-infrared wavelength of 1150 nm. The horizontal line profiles of the absorbance at this wavelength, obtained using a unidirectional transmission imaging technique, were approximated with multi-Gaussian functions to robustly and efficiently apply the inverse Abel transform. In the experiment, a 1-mm-diameter steel sphere in water was heated by electromagnetic induction. The reconstruction results show the formation of spherical temperature distributions within the thermal conduction regime, followed by the occurrence of upward free convection, leading to a laminar plume. The size and shape of the plume depended on the heat generation rate in the sphere. These results were analyzed and verified through a comparison with the results of a numerical simulation on the temperature and flow fields. (C) 2019 Elsevier Ltd. All rights reserved.