In this presentation, documentary sources of climate change will be described and evaluated, and the information gathered from them will be used to cast light on variations in the climate of Iceland over the last 1000 years or so. Prior to AD 1600 the data are fairly sporadic, but after that time it is possible to re-construct temperature and sea-ice indices. A scrutiny of the sources indicates that there has been a great deal of climatic variability from early settlement times to the present day. From ca. 1640 to ca. 1680 there appears to have been little sea ice off Iceland’s coasts. During the period 1600 to 1850, the decades with most ice present were probably the 1780s, early 1800s and the 1830s. From 1840 to 1855 there was virtually no ice off the coasts. From that time to 1860 there was frequent ice again, although the incidence does not seem to have been as heavy as in the earlier part of the century. Further clusters of sea-ice years occurred again from ca. 1864 to 1872. Several very heavy sea-ice years occurred during the 1880s. From 1900 onwards sea-ice incidence falls off dramatically. As regards temperature variations, a cooling trend may be seen around the beginning and end of the seventeenth century. However, these periods are separated by a mild period from ca. 1640 to 1670. The early decades of the 1700s were relatively mild in comparison with the very cold 1690s, 1730s, 1740s and 1750s. The 1760s and 1770s show a return to a milder regime in comparison. The 1780s are likely to have been the coldest decade of the century, but this was compounded by volcanic activity. The 1801s, 1830s and 1880s were also comparatively cold.
keynote lecture