Colonial private diaries and their potential for reconstructing historical climate in Bombay, 1799-1828

Servants of the East India Company and its affiliates carried a preoccupation with the recording of weather and climate. Meteorological observations were collected in observatories set up by the Company, but also within medical journals, travel writings, military records, ships logs and a variety of personal diaries and correspondences. This chapter assesses the contribution of these historical observations to contemporary climate science. Four diaries area analysed from early-nineteenth-century Bombay. These provide information on precipitation intensity, the occurrence of extreme or unusual meteorological events, and temperature variability. Of particular interest are ad-hoc thermometer readings recorded by the four diarists. Analysis of these suggests that monthly extreme temperatures during the period 1799-1828 were around 5˚C lower than the 1973-2013 average. This is likely to be related to a heat-island effect caused by the rapid urbanisation in Bombay/Mumbai during the nineteenth and twentieth centuries, coupled with the effects of anthropogenic climate change.