Projecting temperature-related mortality in Bangladesh under climate change scenarios - considering the role of cold effects and precipitation in future projections
Final Report Abstract
The primary objective of the research project was to systematically investigate the relationship between meteorological drivers and mortality in different sub-populations of Bangladesh and use the derived dose-response functions to project future impacts of weather under climate change scenarios. Special attention was given to effect modifiers, such as age, gender, socioeconomic status and location. Furthermore, the nature of cold effects was investigated with the intention to understand whether the observed increase in mortality with decreasing temperature is a seasonal phenomenon or indeed due to low temperatures. In addition to temperature effects, the impact of precipitation were investigated. We observed an increase in mortality with decreasing temperature, i.e. a cold effect, over a wide range of values while only at the upper end of the temperature distribution, this association changed and mortality started to increase with increasing temperature. This observed heat effect followed a steeper slope than the cold effect. On average, we observed a mortality increase of 2.5 % per 1°C decrease in temperature (cold effect) and an increase of 6.5 % (heat effect) per 1° increase in temperature. Heat effects strongly varied for different subgroups, with strongest effects observed in urban areas (12.0 %) for the elderly (22.0%) and for males (12.9%). Despite the tropical climate, Bangladesh, along with many other low-latitude countries, experiences strong winter and cold related excess mortality. One major objective of this project was to understand the nature of these cold effects and disentangle the role of season vs. temperature and diurnal changes in temperature. Our findings show that while different approaches to seasonality adjustment affected the magnitude of cold effects, coldrelated mortality persisted regardless the adjustment approach, suggesting the relevance of absolute temperatures as compared to season. Different from effects observed in the midlatitudes, cold effects in Bangladesh occurred on a very short time scale highlighting the role of temperature versus season. Insufficient adaptation with regard to housing and clothing might lead to such cold-related increases in mortality despite rather moderate temperature values. Given the high amounts of rainfall in many tropical monsoon areas and the often seasonally pronounced differences, there might be a potentially strong impact on health outcomes and death. Our analyses demonstrated a sharp increase in death risk at very high precipitation amounts during the dry season which is most likely to be cyclone-related. This cyclone effect was most pronounced at the immediate day. At longer lags, we found a negative association between precipitation and mortality indicating some kind of dry effect. During the rainy season, we observed a protective effect of rainfall, which might be due to the mitigation of heat effects. Finally, derived dose response function were linked to future projections of projections of temperature. In this project, we relied on multimodel outputs of 21 Global Climate models obtained through NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP). These data sets comprise projections from the 21 models produced and distributed under the Coupled Model Intercomparison Project Phase 5 (CMIP5). Our findings show strong increases in heat-related deaths for a low greenhouse gas (GHG) as well as high GHG scenario (RCP 4.5 vs. RCP 8.5). The expected decline in cold-related mortality does not offset increases in heat-related mortality, leading to a positive net impact on temperature-related deaths. Estimates show several 10,000 additional annual deaths in the 2020s for both emission scenarios. Estimates for the 2050 keep increasing but show a wider range of uncertainty. The findings of this project highlight the urgent need for heat intervention and adaptation strategies. Effective mitigation measures should involve different time-scales ranging from short-term strategies as implemented within early heat warning systems to more long-term measures involving awareness rising, capacity building in health care providers to urban planning.
Publications
- (2017) Defining and Predicting Heat Waves in Bangladesh. Journal of Applied Meteorology and Climatology 56 (10) 2653–2670
Nissan, Hannah; Burkart, Katrin; Coughlan de Perez, Erin; van Aalst, Maarten; Mason, Simon
(See online at https://doi.org/10.1175/JAMC-D-17-0035.1) - Spatial variations and determinants of infant and under-five mortality in Bangladesh. Health & Place 47, 156-164
Gruebner, O., Khan, MMH, Burkart, K., Lautenbach, S., Lakes T., Krämer, A.
(See online at https://doi.org/10.1016/j.healthplace.2017.08.012) - Is precipitation a predictor of mortality in Bangladesh? A multi-stratified analysis in a South Asian monsoon climate. Science of the Total Environment, 2016, 553: 458–465
Burkart K., Kinney, P.
(See online at https://doi.org/10.1016/j.scitotenv.2016.01.206) - What drives cold-related excess mortality in a South Asian Monsoon Climate – Season vs. temperature and diurnal changes in temperature. International Journal of Biometeorology, 2017, 61 (6), 1073-1080
Burkart, K., Kinney, P.
(See online at https://doi.org/10.1007/s00484-016-1287-8)
