In the first ‘Health Effects of Climate Change (HECC)’ report published in 2002, current and future temperature-related mortality was analysed at UK-level only, estimating a 253% increase in heat-related deaths (1,995 additional deaths) by the 2050s and a decrease in cold-related deaths of 25% (20,292 fewer) for a medium-high emission scenario. For the second HECC report in 2008, historical periods were analysed, suggesting that health effects of consecutive days of heat are greater than separate individual days, and there may be population adaptation to changing temperatures in the future, but future changes in mortality were not estimated explicitly. In the most recent report in 2012, Hajat and colleagues conducted analysis of heat- and cold-related mortality at the regional level in England using UK-focused climate projection data from the UK Met Office (UKCP09) for the 2020s, 2050s and 2080s. Heatrelated deaths were estimated to rise by 257% by the 2050s for the UK as a whole, with the increase partly driven by population growth and ageing. As with the previous reports, specific adaptation actions and interventions were not modelled in future estimates of heat and cold mortality. Although projections of future UK population growth were incorporated by including expected size and age breakdown in future decades, it was assumed the population had not adapted to the effects of heat and cold over time.