Future climate change will cause increasing air temperatures affecting human thermal comfort and health (Smith et al. 2013). A large population in Europe, in particular in Luxemburg - with its dense population and the high number of cross border commuter flows - is vulnerable to the changing thermal stress levels. Most severe health effects could be associated with the projected increase of extreme events (Smith et al. 2013), but adverse effects on human health could already be shown with only moderate levels of heat stress (Hajat and Kosatky 2010, Kovats and Hajat 2008). The objective is to assess the impact of climate change on three different regions of Luxemburg at a high spatial resolution. The assessment will include all classes of the bioclimatic indices, evaluating the changes in time and space.
Materials and methods
Our analysis is based on two bioclimatic indices, the Physiological Equivalent Temperature (PET) (Mayer and Hoppe 1987) and the Universal Thermal Climate Index (UTCI) (Jendritzky et al. 2012). Both indices include the projected input parameters air temperature, wind speed, relative humidity and global radiation. In addition to these parameters, physiological aspects of the human body, such as activity, clothing, sex and age are taken into account (Matzarakis et al. 2007). To assess the influence of climate change on human thermal comfort, we analysed two sets of future climate projections all based on the A1B emissions scenario. To account for uncertainties in the projections, we used a multi-model ensemble of 12 transient simulations with a spatial resolution of 25 km for the period from 1971 until 2098. The differences between three regions in Luxemburg were analysed based on a single regional climate model run with the COSMO-CLM model (spatial resolution: 1.3 km).
Results and Discussion
Based on the multi-model ensemble projections we could show that there is a significant (P <0.05) trend in air temperature, relative humidity, PET and UTCI, whereas wind speed and global radiation do not show trends. Our analyses of the three regions of Luxemburg show that regional differences with regard to thermal comfort exist in present and future climate conditions. We could show for both indices that cold stress levels will decrease significantly in the near future up to 2050, while the increase in heat stress turns significant in the far future up to 2100. Our analysis showed that the lowest bioclimatic indices are found in the north of Luxembourg throughout all time periods. The highest occurrence of hot index classes can be found in the south of Luxemburg. Regional differences that are already present in the reference period remain throughout the following time slices in most cases. All but one index classes above thermal comfort (PET) - respectively no thermal stress (UTCI) - show regional differences in the future periods. Merging the index classes to three categories cold stress no thermal stress and heat stress it can be seen that the number of hours causing any form of cold stress decreases through all stations (-5.6% to -23.4% for the far future). In contrast, the number of hour in the comfortable and heat stress class increase (264.6% to 596.9% heat stress increase in the far future). In total these changes result in fewer hours with thermal stress in the future. The global warming leads to a higher amount of hours in the thermal comfort range for the projected future. As this process continues, hours that are now present in the comfort range might than shift towards heat stress levels. According to Donaldson and Keatinge (1997, 2002) cold temperature increases the risk of mortality. In contrast, a recent study by Staddon et al. (2014) shows that decreasing cold stress does no longer lead to decreasing mortality rates in temperate countries.
Conclusion
Our study confirms the general decrease in cold stress as well as the general increase in heat stress for the region of Luxemburg by analysing the bioclimatic indices PET and UTCI in detail. The analysis revealed that the change in stress levels is caused by significant trends in air temperature and relative humidity. Changes in cold stress tend to appear already in the near future (2041-2050), whereas the heat stress levels changes become significant in the far future (2091-2100). In total the number of hours in index classes that are considered to be stressful for the human body decreases in the future. To evaluate if this also causes a decrease in thermal stress related mortality and morbidity, further studies are foreseen.
Acknowledgements
We gratefully acknowledge the financial support of the National Research Fund in Luxembourg (4965163 - FRESHAIR). Parts of the work have been done in the framework of the Small Particles - environmental behaviour and toxicity of nanomaterials and particulate matter (SMALL) project.
References
Donaldson GC, Keatinge WR (1997) Early increases in ischaemic heart disease mortality dissociated from and later changes associated with respiratory mortality after cold weather in south east England Journal of epidemiology and community health 51:643-648
Donaldson GC, Keatinge WR (2002) Excess winter mortality: influenza or cold stress? Observational study British Medical Journal 324:89-90
Hajat S, Kosatky T (2010) Heat-related mortality: a review and exploration of heterogeneity Journal of epidemiology and community health 64:753-760
Jendritzky G, de Dear R, Havenith G (2012) UTCI--why another thermal index? International journal of biometeorology 56:421-428
Kovats RS, Hajat S (2008) Heat stress and public health: A critical review. In: Annual Review of Public Health, vol 29. Annual Review of Public Health. Annual Reviews, Palo Alto, pp 41-+
Matzarakis A, Rutz F, Mayer H (2007) Modelling radiation fluxes in simple and complex environments--application of the RayMan model International journal of biometeorology 51:323-334
Mayer H, Hoppe P (1987) Thermal comfort of man in different urban environments Theoretical and Applied Climatology 38:43-49
Smith KR et al. (2013) Climate Change 2014: Impacts, Adaptation, and Vulnerability Chapter 11. Human Health: Impacts, Adaptation, and Co-Benefits. IPCC, Cambridge, United Kingdom and New York, NY, USA
Staddon PL, Montgomery HE, Depledge MH (2014) Climate warming will not decrease winter mortality Nature Climate Change 4:190-194
- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner