From Blaise Bullimore, Haverfordwest, Pembrokeshire, UK
There are further factors that could affect city atmospheres and feasibly increase rainfall in urban areas: water vapour released by burning fossil fuels and the use of evaporative cooling (21 September, p 15).
Multi-megawatt quantities of heat and plumes of saturated air are probably being emitted into ambient air around the clock via cooling towers or evaporative refrigeration condensers. Large air conditioning systems, refrigeration-dependent factories, chilled and frozen bulk cold stores and large data processing sites all contribute.
