Climate change may be bad for people but it's good for bugs.
Germs of all kinds, as well as mosquitoes and other disease carriers, will live longer in warmer weather because cold kills them. They'll find more areas with the hot, humid conditions they need to thrive. Disease-carrying insects have already begun to move into new territory, climbing higher up the Andes in South America and reaching farther north into Canada and the U.S. to spread what were once considered tropical diseases like West Nile virus.
"Insect-borne diseases like dengue fever and malaria are now being reported in higher elevations in Asia and Latin America," says Dr. Francesca Dominici, senior associate dean for research in the Department of Biostatistics at Harvard University's School of Public Health. "Mosquitoes that carry malaria are being found in areas where before they would die."
The impact could be devastating. According to the World Health Organization, between 2030 and 2050, the world will see an additional 250,000 deaths a year from malaria, malnutrition, diarrhea and heat stress as a result of climate change.
So the discussions among leaders from around the world at the U.N. Conference on Climate Change, meeting in Paris through Dec. 11, are literally life and death. Last summer, as he announced that the Bill and Melinda Gates Foundation will invest $1 billion in clean energy technology, Bill Gates wrote on his blog: "It would be a terrible injustice to let climate change undo any of the past half-century's progress against poverty and disease — and doubly unfair because the people who will be hurt the most are the ones doing the least to cause the problem." (Note: The Gates Foundation is a funder of NPR.)
Indeed, poor countries are the least equipped to deal with climate change and will see the greatest increase in disease.
"Currently when we estimate health impacts from climate change, far and away the majority of all health damage by climate change is diarrhea mortality, and that will be most pronounced in sub-Saharan Africa," says Dr. Kevin Cromar, director of the Air Quality Program at New York University. "Second to that would be insect-borne diseases, like malaria." Combining health research with economic research is the focus of Cromar's work at the university's Marron Institute of Urban Management. The goal is to develop new models to predict the health consequences of climate change.
Diarrhea and malaria are just two of many concerns.
Climate change unleashes a cascade of events starting with rising temperatures, more extreme weather, rising sea levels and increased air pollution. Rising temperatures will cause more deaths from heat stroke and heart disease. Severe weather events, like floods and droughts will cause deaths from accidents, mudslides and drowning. Rising sea levels will displace people. More heat and drought will fuel forest fires, adding to pollution and causing an increase in asthma, heart and lung disease. All of the climate change consequences will affect food production and clean water supplies, leading to malnutrition, diarrhea, cholera and other bacterial diseases.
People around the world will be forced to migrate. Many will live in squalor with inadequate shelter, sanitation and food.
"People who are poorly off are always going to bear the brunt when things go badly," says Dr. Alfred Sommer, epidemiologist and dean emeritus at Johns Hopkins Bloomberg School of Public Health. But residents of wealthy countries will also suffer. In 1995, 739 people died in one week in a heat wave in Chicago. In Europe in the summer of 2003, at least 70,000 people died in heat waves. Climate change will make heat waves more common. "We know for certain that heat stroke is going to increase," says Sommer.
With enough resources, people in richer countries can mitigate some of the effects of climate change. They can install air conditioning, like many Europeans have done since the heat wave of 2003. They can pack up and move inland or northward. Large hospitals and businesses can install back-up generators on upper floors, after learning from the experience of New York University's Langone Medical Center during Hurricane Sandy. The hospital had to evacuate its 215 patients when a flooded basement back-up power system failed during the storm.
But those solutions are expensive and use energy that increases greenhouse gas, which, in turn, contributes to climate change. "It's a circle that just gets worse and worse, unless we make some dramatic changes to try to reduce the harm," says Sommer.