Climate change impacts on human health span the trajectory of time—past, present, and future. The key finding from the Working Group II, Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) states that health impacts due to climate change have already occurred in the past, are currently occurring and will continue to occur, at least for the foreseeable future, even with immediate reductions in greenhouse gas emissions [ 1]. According to the IPCC, there has been increased heat-related mortality and decreased cold-related mortality in some regions as a result of warming ( Box 1). Moreover, local changes in temperature and rainfall have altered the distribution of some water-borne illnesses and disease vectors. Impacts of climate-related extremes include alteration of ecosystems, disruption of food production and water supply, damage to infrastructure and settlements, morbidity and mortality, and consequences for mental health and human well-being [ 1].
In this special issue of the International Journal of Environmental Research and Public Health ( IJERPH) we present 20 papers that add further weight to the conclusions of the AR5 of IPCC. Grouped in somewhat overlapping categories, three papers assess infectious disease threats from climate change, seven papers heat-related health impacts, one paper ozone-related mortality and nine papers discuss different aspects of adaptation ( Box 2).
Extreme weather events, such as heavy precipitation, are one of the hallmarks of global climate change. Runoff from such precipitation events can result in microbial transport and contamination of coastal water with implications to public health [ 2, 3]. A paper in this special issue of the IJERPH examines these climatic events on beach closures due to high pathogen concentrations in recreational waters and the association with gastrointestinal-related hospital admissions [ 4]. Extreme rain events occurring the previous day were significantly associated with beach closures but not with GI-related hospital admissions. Coastal areas are also at risk for importation of competent disease vectors through cargo shipment. Freight containers (containing used tires or ornamental plants) can harbour the Asian tiger mosquito ( Aedes albopictus) which is a vector for dengue and chikungunya. A paper by Thomas et al., in this issue describes freight container imports into areas in Europe that are climatically suitable for the vector Ae. albopictus [ 5]. The authors model the quantity of cargo imports from areas where the mosquito is endemic into harbours and further dissemination through inland waterways; current and future climatic suitability of the destination area are overlaid to model the long-term establishment of the mosquito.
Human health
Until mid-century, projected climate change will impact human health mainly by exacerbating health problems that already exist (very high confidence). Throughout the 21st century, climate change is expected to lead to increases in ill-health in many regions and especially in developing countries with low income, as compared to a baseline without climate change (high confidence). Examples include greater likelihood of injury, disease, and death due to more intense heat waves and fires (very high confidence); increased likelihood of under-nutrition resulting from diminished food production in poor regions (high confidence); risks from lost work capacity and reduced labor productivity in vulnerable populations; and increased risks from food- and water-borne diseases (very high confidence) and vector-borne diseases (medium confidence). Positive effects are expected to include modest reductions in cold related mortality and morbidity in some areas due to fewer cold extremes (low confidence), geographical shifts in food production (medium confidence), and reduced capacity of vectors to transmit some diseases. But globally over the 21st century, the magnitude and severity of negative impacts are projected to increasingly outweigh positive impacts (high confidence). The most effective vulnerability reduction measures for health in the near-term are programs that implement and improve basic public health measures such as provision of clean water and sanitation, secure essential health care including vaccination and child health services, increase capacity for disaster preparedness and response, and alleviate poverty (very high confidence). By 2100 for the high-emission scenario RCP8.5, the combination of high temperature and humidity in some areas for parts of the year is projected to compromise normal human activities, including growing food or working outdoors (high confidence).
Source: [ 1]Global environmental change has obviously implications for the distribution of infectious diseases in Europe [ 6] and regions with higher adaptive capacities will be able to counteract any climate change impacts from infectious diseases and be less vulnerable than areas with lower adaptive capacities [ 7]. This theme also emerges from the IPCC AR5 that health impacts from climate change should take into account underlying vulnerabilities that can potentially be mitigated or exacerbated by the socioeconomic context [ 1].
A paper by Bowen et al. uses social network analysis to identify key organisational stakeholders involved in adaptation activities, such as government ministries in Cambodia; in contrast, donor agencies, development banks and non-government organisations contribute much less to adaptation strategies [ 16]. Adaptive capacity to extreme weather conditions and infectious diseases depends on effective governance and access to resources. Adaptation strategies for populations most vulnerable to the harmful effects of extreme heat in different settings are discussed in a paper by White-Newsome et al. [ 17]. A paper by Marinucci et al. in this issue presents a framework to systematically use climate projections to guide public health adaptation. The strategy integrates assessments of climate change impacts, vulnerability assessments, modelling of projected health impacts, evidence-based evaluation of intervention options, strategy for implementing interventions, and systematic evaluation of all activities in an iterative framework [ 18]. Since socioeconomic status determines adaptive capacity, global pathways have to be developed to demarcate different options of adaptation to be taken. Kris Ebi describes the implications of five reference socioeconomic development pathways to human health, as they relate to increasing socioeconomic and environmental challenges to adaptation and mitigation [ 19]. These pathways are important to project the adaptive capacity into the future. Moreover, the systematic collection, merging, integration and analysis of environmental and climatic data with epidemiologic data can generate forecasts and predictions of health outcomes that can help to promote resilience to climate change; two papers in this issue discuss the use of such data sources for epidemiologic analyses for future threat evaluations, outbreak management and interventions to reduce disease burden [ 20, 21]. However, these advanced modelling techniques have their limitations too. Anthony McMichael elaborates on the difficulties of conducting global environmental change research: there is a need to examine climate change sensitivity of population health and social stability of past societies; expand the research methods beyond traditional boundaries, and advance trans-disciplinary approaches to forecasting health risk to populations [ 22]. Thus, even with the contributions in this special issue of IJERPH, there are still considerable technical hurdles and obstacles to be taken, not to mention the political ones, in order to advance the field and minimize human health impacts from climate change.