It is important to recognize that climate change is neither the primary driver of human health today nor will it be in the future. Beyond genetics, there are at least three factors fundamental to the good health of an individual and a society.
Access to safe water and good sanitation is basic to good health. It is estimated that 80 percent of all illnesses worldwide are attributable to unsafe water and poor sanitation. More people die each year from this factor than from war and all other forms of violence. Most of these deaths occur in children less than five years of age. More than one billion people do not have access to safe water and good sanitation; nearly all of those are located in the developing world.
Access to food is also essential to good health. Undernourished people receive less than the minimum amount of food needed for sound health and growth. Estimates put the number of undernourished people at one billion, and nearly all of those live in the developing world.
The third factor important to good health is access to health care. People in developed countries spend huge sums on health care while less-developed countries spend little. Per capita health care spending by the top 5 percent of the world population is about 4,500 times the spending of the lowest 20 percent. As the graph above indicates, there is a positive relationship between health care spending and life expectancy, with low health care spending associated with low life expectancy and high spending associated with high life expectancy. There are anomalies. For instance, Cuba, which has essentially the same life expectancy as the US, has excellent health care but spends only 1/25 of what the US spends per person on health care. Despite the fact that it spends about twice as much per capita on health care as other developed countries, the US is only ranked 27th in life expectancy.
Another measure of health care access is doctors per 100,000 people. Here the disparity between developed and less-developed countries is stark. Again, there are anomalies, such as the former communist countries, which have relative high densities of physicians. Moreover, there can be large inequalities even within the most-developed countries where rural areas often have difficulty attracting doctors.
In summary, individuals who live in developed countries have the greatest access to safe water and sanitation, good nutrition, and health care. People who live in the least-developed nations often have unsafe water and poor sanitation, inadequate nutrition, and little access to health care. Therefore, with or without climate change, the general health of residents of the developed countries is good and of the least-developed nations is poor.