Heat stress and mortality in Lisbon Part II. An assessment of the potential impacts of climate change.

Global environmental change, in particular climate change, will have adverse effects on public health. The increased frequency/intensity of heat waves is expected to increase heat-related mortality and illness. To quantify the climatic risks of heat-related mortality in Lisbon an empirical-statistical model was developed in Part I, based on the climate-mortality relationship of the summer months of 1980-1998. In Part II, scenarios of climate and population change are applied to the model to assess the potential impacts on public health in the 2020s and 2050s, in terms of crude heat-related mortality rates. Two regional climate models (RCMs) were used and different assumptions about seasonality, acclimatisation and the estimation of excess deaths were made in order to represent uncertainty explicitly. An exploratory Bayesian analysis was used to investigate the sensitivity of the result to input assumptions. Annual heat-related death rates are estimated to increase from between 5.4 and 6 (per 100,000) for 1980-1998 to between 5.8 and 15.1 for the 2020s. By the 2050s, the potential increase ranges from 7.3 to 35.6. The burden of deaths is decreased if acclimatisation is factored in. Through a Bayesian analysis it is shown that, for the tested variables, future heat-related mortality is most sensitive to the choice of RCM and least to the method of calculating the excess deaths.