Very true. In fact, here it is from Roy Spencer who generates the data ...
How the UAH Global Temperatures Are Produced « Roy Spencer, PhD . More importantly, the absolute temperature at any one point and time, while interesting, is not that important with respect to trends. As long as the "method" is always the same, then the "trend" is the important information. Furthermore, we don't even know what the "average" global surface temperature really is -- because we don't have sufficient thermometers across the globe -- especially over the oceans. And this is why satellite data is so important because it sees the entire earth -- and at many levels.