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The release of greenhouse gases—principally carbon dioxide—into Earth’s atmosphere since the late nineteenth century has contributed to a climate unfamiliar to our species, Homo sapiens. This new climate has already altered the epidemiology of some infectious diseases. Continued accumulation of greenhouse gases in the atmosphere will further alter the planet’s climate. In some cases climate change may establish conditions favoring the emergence of infectious diseases, while in others it may render areas that are presently suitable for certain diseases unsuitable. This chapter presents the current state of knowledge regarding the known and prospective infectious-disease consequences of climate change.
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The term climate change refers to long-term alterations in temperature, precipitation, wind, humidity, and other components of weather. Over the past 2.5 million years, the earth has warmed and cooled, cycling between glacial and interglacial periods during which average global temperatures moved up and down by 4–7°C. During the last glacial period, which ended roughly 12,000 years ago, global temperatures were, on average, 5°C cooler than in the mid-twentieth century (Fig. 8-1).
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The present climate period, known as the Holocene, is remarkable for its stability: temperatures have largely remained within a range of 2–3°C. This stability has enabled the successful population and cultivation of much of the earth’s landmass by humanity. Current climate change differs from that in the past not only because its primary cause is human activities but also because its pace is faster. The 5°C of warming that occurred at the end of the last ice age took roughly 5000 years, whereas such a temperature increment may occur within the next 150 years unless the release of greenhouse gases is substantially reduced in coming decades. The current rate of warming on Earth is unprecedented in the last 50 million years. Climate science, although still a relatively new ...