 The weather and climate conditions that matter most immediately to people are those near the earth’s surface, where they live. Coordinated networks of land-based observing stations—measuring near-surface temperature, pressure, precipitation, humidity and sometimes other variables—began to emerge in the mid-nineteenth century and expanded rapidly in the twentieth century (Fleming 1998: Ch.3). Today, there are thousands of stations around the world making daily observations of these conditions, often overseen by national meteorological services. In recent decades, there have been major efforts to bring together records of past surface observations in order to produce long-term global datasets that are useful for climate change research (e.g., Menne et al. 2012; Rennie et al. 2014). These ongoing efforts involve international cooperation as well as significant “data rescue” activities, including imaging and digitizing of paper records, in some cases with the help of the public.