Indoor climate implications of extreme outdoor climates

Background: Consensus climate modelling projects highly altered climates by 2100 with small but not low probabilities of reaching 6-9 deg mean annual increases in mean global temperature and much larger increases in some regions and seasons. Such temperatures imply increasingly large increases in areas where outdoor work is restricted because of physiological limits due to the local wet bulb globe temperature (WBGT), a function mainly of temperature and humidity, but also considering wind and radiation. A growing literature examines the implications for labour productivity in agriculture, construction, and other outdoor activities over time Aim: Here we examine the potential implications for indoor environments of a world in which outdoor work is increasingly difficult and, eventually perhaps, even impossible in some areas. Methods: We briefly review the existing literature on climate projections, the calculation of WBGT, and implications of extreme WBGTs for work productivity. We review also the implications for indoor work environments and energy demand of increasing demand for air conditioned workplaces as well as households. We calculate monthly indoor heat exposure situations in India, as an example, and discuss global implications. Results: We discuss implications for urban design, patterns of pollution exposures, physical activity for transport and recreation, and work practices in a world in which the human experience is increasingly confined to indoor environments. The effects are not only experienced outdoors as modelling shows seriously increasing indoor heat problems during lengthy periods each year and substantial increases in energy requirements for cooling to avoid serious health impacts and maintain productivity.