The impact of climate change on human health

Climate change has the potential to affect human health in a number of ways. Salt water intrusion in drinking water will affect vulnerable populations in low-lying coastal regions, particularly in South East Asia.  Problems with the future availability of water are a concern in many regions, including remote populations who rely on glacier melt in the South American Andes.

Warmer weather is also expected to have a more direct impact on people’s health by increasing rates of heat-related deaths. It is not clear to what extent (if at all) this may be offset by a decline in excess winter deaths. A recent study concluded that improvements in housing, higher incomes and improved health care have led to a long term decline in excess winter deaths. Since the 1970s, excess winter deaths have no longer been correlated with the number of cold days (days with an average temperature below 5 degrees Celsius) in a given winter. This suggests that winter deaths would not be expected to decline in England and Wales as temperatures increase due to climate change. In a report published in 2011, the National Records of Scotland found no correlation between the overall average temperature in a given winter and the number of excess winter deaths that year. The authors did note however that the average winter temperature may not be the best way to estimate the severity of a given winter.  

xxx1

Professor Majid Ezzati explains how rising temperatures and increased variability could affect temperature-related deaths in the UK.

Research areas

Vector-borne diseases

Climate change and vector-borne diseases

Dr Paul Parham, Honorary Lecturer, School of Public Health, Imperial College London.

Mosquito biting a person's arm Arguably one of the most important effects of climate change is the likely impact on human health. While this may take many forms, the implications for vector-borne diseases are both potentially significant and highly uncertain. Our research aims to establish tools to help map vectors and/or disease transmission, calculate risk, and plan control strategies under a changing climate, a process that is of great importance for tackling both established and emerging diseases. This is a rapidly emerging multi-disciplinary field and translating this research into outputs for use by stakeholders in planning and improving vector and disease control strategies for pathogens that infect millions of people worldwide is vital.

Improvements in vector-borne disease control strategies will have a direct impact on human populations through reducing the burden of established vector-borne diseases or preventing future outbreaks in vulnerable populations. In addition, while climate and climate change are extremely likely to influence the future transmission and range of vector-borne diseases, the magnitude of the effect is likely to vary between diseases. It should be recognised that a multitude of other epidemiological, ecological and socioeconomic factors are also likely to affect disease transmission. Nevertheless, quantifying the role of climate change in future vector-borne disease trends compared to other known drivers represents an important goal.

An important development in recent years in climate modelling has been the development of multi-model ensembles to make projections about future climate scenarios. Such multi-model approaches in climate modelling are almost always found to be superior to the single ‘best’ model in a given ensemble, and these form the basis of the Intergovernmental Panel for Climate Change’s AR4 and AR5 projections. By analogy, our research is currently working towards developing and validating an ensemble of appropriately-weighted climate-driven vector-borne disease models as a means of better understanding the role of climatic and environmental variables on transmission, as well as the impact of climate variability and change on interventions in different settings. In addition to uncertainties in climate modelling and factors surrounding future climate scenarios, considerable uncertainties exist within non-climatic factors known to affect local vector-borne disease transmission. These uncertainties mean it is difficult to develop realistic projections about future transmission patterns and the likely impact of intervention programmes.

Our research seeks to understand how this array of uncertainties in disease epidemiology, vector ecology, parasite biology, and climate modelling, as well as the causal links between these biological, environmental and climatological systems, may be accounted for within multi-model approaches based on a ‘collective consensus’ across a suite of viable models. We are also assessing the cost effectiveness of different intervention measures. This forms a vital component of future public health policy planning.

 

Temperature related death

Heat and cold related deaths in the United Kingdom

Professor Majid Ezzati, Chair in Global Environmental Health, Faculty of Medicine, Imperial College London

Warmer temperatures are expected to lead to an increase in the amount of heat-related illnesses and deaths due to increases in extreme high temperatures and as well as increases in the average temperature. We are trying to understand how much these effects vary between different communities and what the reasons for this variation are.  The hope is that this knowledge will help to identify vulnerable communities, and also to develop ways of minimising the health impacts of warmer weather, both currently and in the future.  

References

Climate warming will not decrease winter mortality. Nature Climate Change. http://www.nature.com/nclimate/journal/v4/n3/full/nclimate2121.html
Winter Mortality in Scotland 2010/11. The National Records of Scotland. http://www.gro-scotland.gov.uk/files2/stats/winter-mortality/winter-mortality2010-11.pdf