Instrumental records are becoming long enough to show trends in climate, although the distinction between trends and longer cycles is never simple. The Little Ice Age set the stage for the global warming of the last century, which probably had both natural and anthropogenic causes (Intergovernmental Panel on Climate Change, 2001b). A brief review of some of the main trends is provided here, showing that these trends often exhibit regional abruptness and are linked to modes of climate variability, again documenting the importance of instrumental records to the study of abrupt climate change.

Most long instrumental records were initiated in the nineteenth and twentieth centuries. The central England temperature time series is one of the longest continuous instrumental climate records (Figure 2.6), and it cap-

FIGURE 2.6 The Central England temperature time-series is one of the longest continuous instrumental records of climate change, with data from 1659 to 2000. Top figure shows summer and bottom figure shows winter. Temperature scale is in degrees Celcius. (Data courtesy of P. Jones, University of East Anglia.)