The 21st Century climate challenge

donors to invest in rehabilitation. The problemis that climate change is a powerful force pullingin the other direction.Human health and extremeweather eventsIPCC projection: Climate change will affecthuman health through complex systemsinvolving changes in temperature, exposure toextreme events, access to nutrition, air qualityand other vectors. Currently small healtheffects can be expected with very high confidenceto progressively increase in all countriesand regions, with the most adverse effects inlow-income countries.Human development projection: Climate willinteract with human health in diverse ways.Those least equipped to respond to changinghealth threats—predominantly poor people inpoor countries—will bear the brunt of healthsetbacks. Ill-health is one of the most powerfulforces holding back the human developmentpotential of poor households. Climate changewill intensify the problem.Climate change is likely to have majorimplications for human health in the21 st Century. Large areas of uncertainty surroundassessments, reflecting the complex interactionbetween disease, environment and people.However, in health, as in other areas, recognitionof uncertainty is not a case for inaction. TheWorld Health Organization (WHO) predictsthat the overall impact will be negative. 110Public health outcomes linked to climatechange will be shaped by many factors.Pre-existing epidemiology and local processeswill be important. So, too, will pre-existinglevels of human development and thecapacities of public health systems. Many ofthe emerging risks for public health will beconcentrated in developing countries wherepoor health is already a major source of humansuffering and poverty—and where publichealth systems lack the resources (human andfinancial) to manage new threats. An obviousdanger is that climate change under theseconditions will exacerbate already extremeglobal inequalities in public health.Malaria gives rise to some of the greatestcauses for concern. This is a disease that currentlyclaims around 1 million lives annually, over90 percent of them in Africa. Some 800,000children under the age of 5 in sub-Saharan Africadie as a result of malaria each year, making itthe third largest killer of children worldwide. 111Beyond these headline figures, malaria causesimmense suffering, robs people of opportunitiesin education, employment and production, andforces people to spend their limited resources onpalliative treatment. Rainfall, temperature andhumidity are three variables that most influencetransmission of malaria—and climate changewill affect all three.Increased rain, even in short downpours,warmer temperatures and humidity create a‘perfect storm’ for the spread of the Plasmodiumparasite that causes malaria. Rising temperaturescan extend the range and elevation of mosquitopopulations, as well as halving incubationperiods. For sub-Saharan Africa in particular,any extension of the malaria range would posegrave risks to public health. Some four in fivepeople in the region already live in malarialareas. Future projections are uncertain, thoughthere are concerns that the malarial range couldexpand in upland areas. More disconcertingstill, the seasonal transmission period mayalso increase, effectively increasing average percapita exposure to malarial infection by 16–28percent. 112 Worldwide it is estimated that anadditional 220–400 million people could beexposed to malaria. 113Changing weather patterns are alreadyproducing new disease profiles in many regions.In eastern Africa, flooding in 2007 creatednew breeding sites for disease vectors suchas mosquitoes, triggering epidemics of RiftValley Fever and increasing levels of malaria.In Ethiopia, an epidemic of cholera followingthe extreme floods in 2006 led to widespreadloss of life and illness. Unusually dry and warmconditions in eastern Africa have been linked tothe spread of chikungunya fever, a viral diseasethat has proliferated across the region. 114Climate change could also increase thepopulation exposed to dengue fever. This is ahighly climate-sensitive disease that is currentlyChanging weatherpatterns are alreadyproducing new diseaseprofiles in many regions2Climate shocks: risk and vulnerability in an unequal worldHUMAN DEVELOPMENT REPORT 2007/2008 105