IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability

8.1 Introduction

This chapter describes the observed and projected health impacts of climate change, current and future populations at risk, and the strategies, policies and measures that have been and can be taken to reduce impacts. The chapter reviews the knowledge that has emerged since the Third Assessment Report (TAR) (McMichael et al., 2001). Published research continues to focus on effects in high-income countries, and there remain important gaps in information for the more vulnerable populations in low- and middle-income countries.

8.1.1 State of health in the world

Health includes physical, social and psychological well-being. Population health is a primary goal of sustainable development. Human beings are exposed to climate change through changing weather patterns (for example more intense and frequent extreme events) and indirectly though changes in water, air, food quality and quantity, ecosystems, agriculture, livelihoods and infrastructure (Figure 8.1). These direct and indirect exposures can cause death, disability and suffering. Ill-health increases vulnerability and reduces the capacity of individuals and groups to adapt to climate change. Populations with high rates of disease and debility cope less successfully with stresses of all kinds, including those related to climate change.

In many respects, population health has improved remarkably over the last 50 years. For instance, average life expectancy at birth has increased worldwide since the 1950s (WHO, 2003b, 2004b). However, improvement is not apparent everywhere, and substantial inequalities in health persist within and between countries (Casas-Zamora and Ibrahim, 2004; McMichael et al., 2004; Marmot, 2005; People’s Health Movement et al., 2005). In parts of Africa, life expectancy has fallen in the last 20 years, largely as a consequence of HIV/AIDS; in some countries more than 20% of the adult population is infected (UNDP, 2005). Globally, child mortality decreased from 147 to 80 deaths per 1,000 live births from 1970 to 2002 (WHO, 2002b). Reductions were largest in countries in the World Health Organization (WHO) regions of the Eastern Mediterranean, South-East Asia and Latin America. In sixteen countries (fourteen of which are in Africa), current levels of under-five mortality are higher than those observed in 1990 (Anand and Barnighausen, 2004). The Millennium Development Goal (MDG) of reducing under-five mortality rates by two-thirds by 2015 is unlikely to be reached in these countries.

Non-communicable diseases, such as heart disease, diabetes, stroke and cancer, account for nearly half of the global burden of disease (at all ages) and the burden is growing fastest in low- and middle-income countries (Mascie-Taylor and Karim, 2003). Communicable diseases are still a serious threat to public health in many parts of the world (WHO, 2003a) despite immunisation programmes and many other measures that have improved the control of once-common human infections. Almost 2 million deaths a year, mostly in young children, are caused by diarrhoeal diseases and other conditions that are attributable to unsafe water and lack of basic sanitation (Ezzati et al., 2003). Malaria, another common disease whose geographical range may be affected by climate change, causes around 1 million child deaths annually (WHO, 2003b). Worldwide, 840 million people were under-nourished in 1998-2000 (FAO, 2002). Progress in overcoming hunger is very uneven. Based on current trends, only Latin America and the Caribbean will achieve the MDG target of halving the proportion of people who are hungry by 2015 (FAO, 2005; UN, 2006a).