Before showing the modeling results for the modern era, it is instructive to show the amount of data now available for analysis, as opposed to what is used for paleo- climates. When one computes the global average temperature, isn’t that just a weighted average over a finite number of places on the earth, say, a few hundred? Now that we have satellites, the coverage is much better. Here are three examples. Figure 1.6 shows the tremendous increase in the number of measurements of ocean temperature between the 1950s and the 1990s. Figure 1.7 shows the fine detail that satellite coverage gives on the altitude change in each part of Greenland and Antarctica. The loss of ice thickness can be seen clearly where glaciers and ice sheets have slid into the sea. Figure 1.8 shows the distribution of aerosols over the globe as obtained by opacity measurements by satellites. This is supplemented by a finite number of ground-based observations which can also determine the size and material of the particulate matter.