Instrumental and documentary archives of past environmental change

Instrumental climate records

Instrumental data serve a variety of purposes in palaeo-environmental study:

1. They make it possible to quantify objectively how the climate has varied in recent times and provide the most statistically robust data from which to establish the short-term spatial and temporal coherence of those modes of variability (see 7.6) recognisable in the climate system at the present-day.

2. They provide the basis on which diverse proxies (see below) can be calibrated to measured climatic properties, using statistical expressions that either capture the links between their current distributions and present-day climate, or express their responses to climate variability over some recent time interval for which instrumental records are available.

3. They form a link between the longer, proxy records available from environmental archives and the period of present-day monitoring.

The longest series of instrumental observations of the weather is for the English Midlands and goes back into the seventeenth century. In this instance, careful evaluation of each instrumented site and measurement has made possible a detailed record of climate change from AD 1659 onwards (Manley, 1974) (see Figure 4.1). In most parts of the world, there are very few reliable instrumental series that go back more than 100 years. For part of the span of time over which reliable, instrumental records are available, one of the most powerful tools for reconstructing past atmospheric conditions is what is termed reanalysis.