**3. Quantification of the Health Impacts of Temperature Changes**

The environment, weather and climate all have profound impacts on health, either through direct associations or through less obvious pathways, which can make quantification difficult. However, one of the most widely studied, and therefore the most well understood impacts of climate change on health is through direct changes in temperature, which can increase the risk of illness and hospitalization, or lead to premature mortality.

Kinney [16] presents a comprehensive, up to date review of the relationship between temperature and health impacts (from both heat and cold), from morbidity to mortality, in different global regions, as well as how these relationships have changed over time. Heat-mortality relationships have been shown to vary by geographic region and population group, but less well studied is how relationships may have changed over time. Kinney reviews the emerging literature to try to answer this question, and gives guidance on taking account of trends over time and space when projecting future impacts of climate change and the associated change in temperature [16].

There are further research papers addressing the effects of temperatures on health in this issue, including analyses on heatwaves and cold spells, and reduced productivity in relation to heat. Two of the papers in this special issue focus on the incidence of heatwaves [17] and cold spells [18] over a 50 year period (1966–2015) in the city of Poznan, Poland. The authors highlight how the diversity of land type is reflected by diverse thermal conditions across the city compared with the reference monitoring stations, and the increased frequency of heatwave and reduced frequency of cold spells over the period studied.

Muthers et al. [19] pinpoint specific heatwave events which occurred during the years of 2003 and 2015, and estimate the resulting heat-related mortality in South West Germany. Results showed daily mortality anomalies reached +70% and +56% during the summers of 2003 and 2015, respectively, and climate projections indicate the increasing probability of comparable heatwaves occurring every second summer in the near future (2021–2050s) [19].

As well as leading to premature mortality, high temperatures and heat stress can also be detrimental to productivity. This can be a difficult effect to quantify, and is a subject tackled by Dear [20]. Here, a modelling approach is adopted which aims to build on existing evidence and which can express productivity as a function of environmental heat, and considers variations between individual workers [20].
