Analyses of the conventional surface meteorological observations indicate that the near-surface air temperature of the Earth as a whole has increased by about 0.6 °C over the last century (IPCC, 2007). However, the patterns of surface change across the Earth in the instrumental era are complex and sensitive to the period examined. Many studies highlight that some of the largest environmental changes have taken place at high latitudes.
In this chapter we are concerned with high latitude atmospheric, oceanic and cryospheric changes over the period for which there are a reasonable number of in-situ instrumental records. This is obviously shorter than for the more populated mid latitude regions and covers only about the last 100 to 150 years in the Arctic, and about 50 years in the Antarctic. The first long meteorological records started in Europe during the seventeenth century at locations such as Paris and London, but measurements from the Arctic generally began during the nineteenth century. However, as will be discussed later, there are several Arctic or near-Arctic temperature records that extend back to 1840–1860, such as those from Murmansk, Russia and Reykjavik, Iceland, and around a dozen starting from the second half of the nineteenth century. The greatest increase in the number of Arctic meteorological records came over 1930–40, and later in this chapter we discuss the temperature records from 59 stations in the high latitude areas of the Northern Hemisphere that provide reasonable longitudinal coverage over the areas around the Arctic Ocean.