Impacts on Human Health due to Climate Change Induced Ocean Alterations

Waterborne pathogens such as red tides, ciguatera, and cholera all could increase as a result of climate change, harming fish stocks and consumers alike¹⁵. However, direct impact on human health is difficult to anticipate. Where climate change enhances the spread of disease carried by fish, mosquitoes and other species, human health will obviously be adversely affected¹⁶. In addition, it is possible that where warmer water temperatures cause more marine species diseases, those species may become unsafe for human consumption—much as “red tides” and other algal outbreaks have already affected the food supply. Further disruption to the food supply and thus to human health could come from saltwater intrusion into coastal agriculture lands, destruction of agriculture and transportation infrastructure in storms and floods, and changes in precipitation patterns that reduce agricultural productivity.

Patterns of mortality in large urban populations, which may change as a result of hotter summers and less cold winters, could cause higher death rates in the very old and the very young (witness the deaths associated with the heat wave in France last year). If a region becomes dryer or the rainfall less regular, there may be more particulate matter in the air and thus there will be increased problems related to respiration. In addition, if the heat reduces ultraviolet radiation protection in the atmosphere, it can be expected we will see more skin cancer in some regions. We have already observed this with the case of ozone depletion in which some countries have had to adopt new health policies in respond.

Coastal flooding and the offshore formation of hurricanes and all the other ocean-related extreme weather events are sources of human mortality that may increase. And such events, in conjunction with other forms of food supply disruption, could increase forced migration and relocation—which often in turn generate conditions that increase the risk of disease¹⁷.

Geopolitical Instability

Recent research suggests that there is a possibility that gradual global warming could lead to a relatively abrupt slowing of the ocean’s thermohaline conveyor, which could lead to harsher winter weather conditions, sharply reduced soil moisture, and more intense winds in certain regions that currently provide a significant fraction of the world’s food production. With inadequate preparation, the result could be a significant drop in the human carrying capacity of the Earth’s environment¹⁸.

There are some indications today that global warming has already reached the threshold where the thermohaline circulation could start to shift. The North Atlantic is substantially less salty as the result of "being freshened by melting glaciers, increased precipitation, and fresh water runoff . . . over the past 40 years."¹⁹  A U.S. Department of Defense report analyzes how such an abrupt climate change scenario could de-stabilize current geo-politics, leading to skirmishes, battles, and even war over resource constrictions such as: 1) Food shortages due to decreases in net global agricultural production; 2) Decreased availability and quality of fresh water in key regions due to shifted precipitation patterns, causing more frequent floods and droughts;  and 3) disrupted access to energy supplies due to extensive sea ice and storminess.

The U.S. Department of Defense report predicts that as glacial ice melts, sea levels rise and as wintertime sea extent decreases, ocean waves increase in intensity, damaging coastal cities. Additionally millions of people are put at risk of flooding around the globe (roughly 4 times 2003 levels), and fisheries are disrupted as water temperature changes cause fish to migrate to new locations and habitats, increasing tensions over fishing rights²⁰.

The study done for the U.S. Department of Defense has, of course, been criticized. On the other hand, recent publications offer confirmation of the use of the theory behind the Pentagon scenario. What these and the Pentagon report indicate is that a significant cooling in some places could be part of climate change, that both global warming and cooling will disrupt the balance of natural systems and thus international relations, and that we must act to reverse the trends to avoid political instability.

¹⁵ Stevens, William K. “Linking Health Effects to Changes in Climate” New York Times, August 10, 1998.

¹⁶ See Shope, R. E. 1992. Impacts of global climate change on human health: Spread of infectious disease. Chapter 25 of Global climate change: Implications, challenges and mitigation measures, ed. S. K. Majumdar, L. S. Kalkstein, B. Yarnal, E. W. Miller, and L. M. Rosenfeld, 363-70. Easton, PA: The Pennsylvania Academy of Science. Available at http://www.ciesin.org/docs/001-367/001-367.html

¹⁷ For more information on health impacts, see the 2000 US Global Change Research Program’s “National Assessment of Climate Change” health issues analysis available at:
http://www.usgcrp.gov/usgcrp/Library/nationalassessment/overviewhealth.htm

¹⁸Schwartz, P. and D. Randall. 2003. An Abrupt Climate Change Scenario and Its Implications for United States National Security, Prepared for the Office of the Secretary of Defense, Washington DC, page 1

¹⁹Schwartz, P. and D. Randall. 2003. An Abrupt Climate Change Scenario and Its Implications for United States National Security, Prepared for the Office of the Secretary of Defense, Washington DC, page 3

²⁰Schwartz, P. and D. Randall. 2003. An Abrupt Climate Change Scenario and Its Implications for United States National Security, Prepared for the Office of the Secretary of Defense, Washington DC, page 9