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1. Introduction

Published onApr 10, 2020
1. Introduction

Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.

—Preamble to the constitution of the World Health Organization, April 1948

When we saw the first pictures of the earth as viewed from space, it became evident that we are a small part of a system that is vast, complex, and interconnected. As scientists have learned more about the intricacy of these systems, we have discovered that life depends on their integrity. We barely understand some of the elements of even the simplest systems and are completely ignorant about altogether too many others. One of the fundamental goals of scientific, economic, geographical, and psychosocial research—as well as formal examinations of numerous other areas of study—is to better understand our world so that we may profit from this knowledge.

The law of unintended consequences tells us that intentional or unplanned incursions that involve these life-sustaining systems may produce an unforeseen result. To restate a point made by Donald Rumsfeld when he discussed the possibility of weapons of mass destruction in Iraq: “We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don’t know we don’t know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend[s] to be the difficult ones.”1 Rumsfeld’s admonition certainly applies to climate change, for which the consequences of complexity are dismissed by those who believe that it is a hoax and embraced by those who believe that it is real and happening right now.

To begin to understand the law of unintended consequences, extrapolate this simple example to the billions of interconnected systems that depend on the earth’s climate. Three-toed sloths make a weekly, energy-consuming trip to the ground. Sloths have few enemies in the trees where they live. On the ground, predators are everywhere. What evolutionary advantage does this perilous trip confer on the sloths, and why do they make the trip? They make it to defecate. Research has shown that this act is a critical step in the sloth’s life cycle.2

A unique species of moths that lives in the sloth’s fur lays its eggs in the newly deposited dung: this is the only dung that will do. Newly hatched juvenile moths fly up to the forest canopy to find and live in the fur of the needed sloth. They then live out their entire lives in the sloth’s fur, but the story does not end there. After the moths die, their bodies sustain algae that also live in the sloth’s fur. These algae are the primary source of the sloth’s nutrients; without the algae, the sloths would starve. An unintended disruption of this cycle could lead to the extinction of both the moths and the sloths.

The next example is perhaps more relevant to considerations of climate change. On September 4, 1882, Thomas Edison threw a switch that started the flow of electricity from the newly completed Pearl Street Station to John Pierpont Morgan’s nearby office. Although the coal ash from the power plant quickly became a problem, there was no way that Edison could have known that the carbon dioxide produced by the coal that was burned in the power plant would start to change the climate. Now, more than a century and a quarter later, we know that burning coal and other fossil fuels injects billions of tons of carbon dioxide into the atmosphere each year. Scientific research has shown conclusively that this greenhouse gas is the most important factor driving climate change. Many who are dedicated to preserving and improving public health are convinced by the evidence that climate change poses an unprecedented threat to human health and the environment.

A recent report by the Lancet Commission on Health and Climate Change takes a more positive position, regarding the challenge we face as an unprecedented opportunity.3 It is the totality of the environment that sustains the sloths and countless other species. Ultimately, the environment sustains all living creatures. Sloths are powerless to act. Are we also powerless? Or will we take advantage of the immense and diverse body of knowledge that we and those who have gone before us have worked so hard to acquire in order to act in our own self-interest?

Ecosystems and Health

In 2000, then Secretary-General of the United Nations Kofi Annan called for a report that is now known as the Millennium Ecosystem Assessment. The portion of this report that focused on the relationships between human well-being and the environment was published in 2005.4 In addition to evaluating the effects of changes in the ecosystem on health, the report also sought to place the need for sustainable uses of ecosystems on a firm scientific footing. Some of the report’s conclusions about linkages between ecosystems and health are portrayed in figure 1.1. The report is based on several postulates:

Figure 1.1 Critical relationships between climate change ecosystem effects and human health. Adapted from figure SDM 1 in C. Corvalán, S. Hales, A. J. McMichael, Millennium Ecosystem Assessment (Program), and World Health Organization, Ecosystems and Human Well-Being, Health Synthesis: A Report of the Millennium Ecosystem Assessment (Geneva: World Health Organization, 2005).

  • Ecosystems are the basis for the support of human and other forms of life.

  • “Services” provided by ecosystems, such as providing food, water, and air, are a fundamental requirement for health, as defined by the World Health Organization at the beginning of this chapter.

  • The ecosystems that we depend on, as illustrated by the sloth/moth cycle, are complex because factors that modify them may be direct, indirect, or displaced in time, as illustrated by Edison’s power plant.

A great deal of this book will be devoted to comprehensive discussions of how climate change affects the services provided by ecosystems and the impacts on health caused by the changes that have already occurred or that are likely to occur as the result of climate change.

Aspirations for the Future

In 2000, the United Nations (UN) also sought to identify the most important goals for future development. In September of that year, with the support of numerous international organizations, all 183 members of the UN General Assembly adopted the Millennium Declaration. This unanimous action identified eight Millennium Development Goals (MDGs) that member nations hoped to achieve over the course of the next fifteen years. The goals were ambitious, many addressed health, and many are affected by climate change. They were

  • to eradicate extreme poverty and hunger;

  • to achieve universal primary education;

  • to promote gender equality and empower women;

  • to reduce child mortality rates;

  • to improve maternal health;

  • to combat HIV/AIDS, malaria, and other diseases;

  • to ensure environmental sustainability; and

  • to develop a global partnership for development.

The millennium is over, and progress toward achieving the MDGs was uneven but substantial, as summarized by the UN’s 2015 report.5 The hoped-for two-thirds reduction in childhood mortality did not occur, in spite of good progress. The member nations did not reach the goal for reduced maternal mortality. Too often, diseases such as malaria—one of many affected by climate—keep poor children from attending school, which impairs their ability to climb out of poverty, as described in more detail in chapter 5. Sadly, environmental sustainability is not yet within reach.

The environment and climate change are a major focus of the post-2015 UN efforts, as described by UN Secretary-General Ban Ki-moon, who wrote in his report to the General Assembly: “All voices have called for a people-centered and planet-sensitive agenda to ensure human dignity, equality, environmental stewardship, healthy economies, freedom from want and fear, and a renewed global partnership for sustainable development.”6 The Sustainable Development Goals successor to the MDGs includes seventeen objectives, including taking “urgent action to combat climate change and its impacts.” The Secretary-General identified the following six essential elements that are required to meet sustainable development goals for the future:

  1. Dignity: to end poverty and fight inequalities

  2. Prosperity: to grow a strong, inclusive, and transformative economy

  3. Justice: to promote safe and peaceful societies and strong institutions

  4. Partnership: to catalyze global solidarity for sustainable development

  5. Planet: to protect our ecosystems for all societies and our children

  6. People: to ensure healthy lives, knowledge, and the inclusion of women and children

These goals have a familiar ring, but they have a more direct focus on climate change and the related goal of sustainable development.

Sustainable development depends on mitigating and adapting to climate change. This effort must begin with effective measures to curb the emission of greenhouse gases, particularly carbon dioxide. In spite of professed aspirations to limit carbon dioxide emissions, the nations of the world, including developed and undeveloped economies, continue to burn vast amounts of coal to generate badly needed electricity. This is a particular problem in China, the leading emitter of this gas; until recently, the unchecked combustion of coal was seen as being vital to China’s expanding economy. In the United States, cries to “stop the war on coal” make it difficult for the Environmental Protection Agency (EPA) to exercise its authority under the Clean Air Act and curb carbon dioxide emissions by new and existing power plants, as described in the Clean Power Plan and related regulations.

But there is hope. In the run-up to the 2015 Conference of the Parties to the United Nations Framework Convention on Climate Change (COP21/CMP11), otherwise known as Paris 2015, the United States, China, Brazil, India, and other nations announced that they are poised to take the needed steps. It remains to be seen what will actually happen.

Burden of Disease

To develop effective policies and allocate the resources needed to improve health, it is necessary to define a starting point. What are the factors that place health at risk? A project funded by the World Bank in 1990 attempted to answer this question. This report underwent a major update with the launch of a project known as the Global Burden of Disease Study 2010. The results of the efforts of a consortium of institutions were published in The Lancet in 2012. The first part of the report is a global assessment of over two hundred causes of death, broken down into different age groups, with a comparison to similar data from 1990.7 Like its predecessor, this report evaluates what has already happened and draws few conclusions about the future.

A summary of selected elements of the Burden of Disease report is shown in table 1.1. Worldwide, ischemic heart disease is the leading cause of death. It is discouraging to see that this burden is about 35 percent higher than it was at the time of the 1990 report. Stroke follows in second place with a 25 percent increase. In spite of progress in combating HIV/AIDS, there was a huge, almost 400 percent increase in deaths caused by the AIDS virus when compared to the 1990 data. Deaths due to tuberculosis and diarrhea both fell. Reported deaths due to malaria rose by just over 20 percent in the interval. Unfortunately, not all agencies or groups have used the same time frame for evaluating the malaria burden data. This has led to multiple answers and confusion. Malnutrition due to a lack of protein in diets, particularly among children, fell by just over 30 percent. Climate change is quite likely to have substantial effects on malaria and malnutrition, as discussed in subsequent chapters. Progress in the fight against undernutrition is a particular concern. The effects of higher temperatures and changes in rainfall already have made substantial impacts on the world’s food supply.

Table 1.1 Selected causes of death

Rank and cause

Mean rank (95% UI*)

Change from 1990 (95% UI*)

1: Ischemic heart disease

1.0 (1 to 1)

35 (29 to 39)

2: Stroke

2.0 (2 to 2)

26 (14 to 32)


3.4 (3 to 4)

-7 (-12 to 0)

4: Lower respiratory infections

3.6 (3 to 4)

-18 (-24 to -11)

5: Lung cancer

5.8 (5 to 10)

48 (24 to 61)


6.4 (5 to 8)

396 (323 to 465)

7: Diarrhea

6.7 (5 to 9)

-42 (-49 to -35)

10: Tuberculosis

10.1 (8 o 13)

-18 (-35 to -3)

11: Malaria

10.3 (6 to 13)

21 (-9 to 56)

21: Protein energy malnutrition

21.5 (19 to 25)

-32 (-42 to -21)

*UI = uncertainty interval, the range of estimates that includes 95 percent of the expected answers computed from data used to define the cause of death.

The second part of the report on the Global Burden of Disease Study describes sixty-seven risk factors for the global burden of disease.8 Risk factors, disability-adjusted life years (DALYs, or the sum of the years of life lost due to premature death and the years lost to disability), and worldwide deaths excerpted from this report are shown in table 1.2. Hypertension is the leading risk factor and has a clear causal link to ischemic heart disease and stroke. Although the report does not attempt to define the importance of air pollution in the pathogenesis of hypertension as well as other diseases, the link seems clear based on the conclusions of a committee of the American Heart Association and my 2012 book, The Silent Epidemic: Coal and the Hidden Threat to Health.9

Table 1.2 Risk factors for disease, worldwide

Although enormous progress has been made in reducing hypertension-related deaths in the United States, the aforementioned report shows that such deaths remain a serious problem worldwide. Indoor and ambient small particle concentrations (PM2.5, particles with an aerodynamic diameter less than 2.5 microns) are clearly identified as leading risk factors (see also chapter 7). Dietary deficiencies, many of which are or are potentially affected by climate, were also identified as substantial risk factors. Climate change is likely to be increasingly important as a driver of undernutrition, particularly among children, as will be described in subsequent chapters.

There was a great deal of good news in the Millennium Development Goal and Global Burden of Disease reports. Not nearly as many children less than five years of age are dying, deaths due to malaria and HIV are falling—particularly in the most recent years covered, and the toll of infectious diseases has fallen. In the most developed parts of the world, there has been substantial progress toward reducing the mortality associated with heart disease and cancer, which are still the two leading causes of death among Americans. As a result of all of these factors, the life expectancies for both men and women are increasing.

The Global Burden of Disease reports, like all others, are completely dependent on the methods employed by a large and diverse group of researchers. This can be illustrated by the results of a study of aging adults that concluded that there were 503,400 deaths due to Alzheimer’s disease among Americans who were seventy-five years of age or older in 2010.10 This toll is enormously higher than the estimate of approximately 84,000 deaths made by the Centers for Disease Control, and the resulting discrepancy would raise Alzheimer’s disease from sixth to third place in the nation. The difference lies in a prospective study of defined cohorts in the high death study versus an analysis of death certificates in the low death study. The explanation centers on the fact that patients who have Alzheimer’s disease often die from pneumonia. The underlying dementia may not appear in the official death records. Are there similar factors confounding the Global Burden of Disease and Millennium Development Goal studies? It is possible, but these are the best data available.

The Intergovernmental Panel on Climate Change (IPCC) Working Group II’s contribution to its Fifth Assessment Report begins to introduce climate change into a consideration of the earth’s burden of disease. The IPCC estimated that what it terms climate-altering pollutants were responsible for 7 percent of the global disease burden.11 The full report by this working group paints a potentially bleak picture of the future world if unbridled emissions of greenhouse gases are combined with inadequate measures to improve energy efficiency and transition to sustainable sources of energy, along with a failure to make the adaptations needed to minimize the effects of rising oceans, more extreme weather events, and the higher temperatures that are likely.12

The Trajectory toward the Future

Virtually all of us who believe that climate change is real, that human activity is largely the cause, and that prompt actions are badly needed to prevent future ramifications are dismayed by the failure of our institutions to take needed steps. We must move in a direction that is protective of human health and the environment, that helps to meet the Sustainable Development Goals, and that relieves pressure on the causes of morbidity and mortality enumerated by the Global Burden of Disease Study. The authors of a framework for approaching these issues list the following items that must be addressed together to mitigate and adapt to our changing climate:13

  • Political leadership needed to instigate and support the process

  • Institutional organizations that can execute policy

  • Extensive stakeholder involvement

  • Climate change information—a primary objective of this book

  • Use of decision analysis and decision-making tools

  • Explicit consideration of barriers

  • Funding

  • Development and spread of needed technology

  • Research

Examples of how elements of this schema apply to the Florida Keys and the Netherlands are presented in chapter 10.

Without political leadership, the whole process fails. Little or no progress will be made. At the present time, sufficient political leadership is absent. In the United States, President Obama’s administration has taken steps to mitigate climate change, primarily via rules (or protections, as I prefer to call them) promulgated by the EPA. Many in the environmental community regard these steps as too little, too late, and they have been and will continue to be met by stiff and well-financed opposition. Partisanship in the US Senate and particularly the House of Representatives is at an all-time high. Not surprisingly, the nations with the most to lose and the least influence have been the most adamant that something must be done—and soon. President Tong of Kiribati has said, “Our people will have to move.” He expects his island nation to be inundated by a rising sea level, as described in chapter 6.

Political will goes only so far. Detailed and specific plans must be created by institutional organizations that will accomplish defined objectives designed to mitigate or adapt to climate change. Without adequate funds and the institutional organizations needed to formulate policy into workable steps, nothing will happen. The steps most likely to be taken are those that have been labeled as “no regrets” adaptations or mitigating steps—those that can be justified under any possible circumstances, including the absence of climate change.14

Psychologists have studied decision analysis in detail. To fail to use the best methods to make important decisions risks failure. Evidence-based decision analysis should be employed widely in making plans for the future. This is a critical focus of contemporary medical practice.

Finally, there must be strong and well-funded support for education as well as research and development programs. This is the only way to make the technological advances that will insure the ability of societies to cope with present and future challenges in the most efficient and appropriate manner.

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