Seeking clarification here. As a climate change sceptic, I loosely follow several blogs that offer critical views of the science behind the idea of global warming, but I am not especially across the breadth of the science. One of the things I struggle to understand is the idea of 'surface temperature'. Or more exactly, what is meant by this. When we talk of the surface temperature of the moon, we are talking about the temperature of the moon's actual surface (or at least, I presume we are). I assume this is inferred from measuring the moon's spectrum of radiation? Without an atmosphere, it is easy enough to establish an actual, and an average, temperature. The earth's temperature however, as considered by the various temperature indices, is measured by thermometers. These are generally measuring the air temperature several feet above the surface. They are not measuring any surface at all. This is easy to see by noting the differences in temperature depending on whether the thermometer device is in shade, in direct sun, near a heat source, or if a hot or cold wind is blowing. I *think* that the sea temps, as measured by water sampling in times past, or Argo floats etc now, are measuring the water temperature itself, hence it is measuring a surface. But surely ocean temps so derived are not directly comparable with air temps over land? My questions then, are: 1. Is the use of the term 'surface temperature' for the various indices sloppy nomenclature? 2. Should ocean and air temps be combined (if in fact they are)? 3. Is the earth's average temperature as expressed in terms of the greenhouse effect (ie 14C rather than -18C) derived from these indices, or is it derived from measurements from space of earth's radiating temperature (as is done for the moon)?