Space & Innovation

11 Health Threats from Climate Change

Deadly storms, such as Typhoon Haiyan, represent only one way the effects of climate change may devastate livelihoods and harm human health.

Naderev Saño, the Philippine's delegate at the United Nations Climate Change talks currently occurring in Warsaw, announced that he would go on a hunger strike until a meaningful outcome of the talks was in sight. Typhoon Haiyan ripped through Saño's hometown, Tacloban City, on Nov. 8, leaving thousands dead and many more lives ruined. Saño pointed out that massive killer storms, like Haiyan, Hurricane Katrina and Superstorm Sandy, may receive some of their power from the warming climate.

As the atmosphere warms, that heat energy may be transformed into a 2- to 11-percent increase in the intensity of tropical storms by 2100, according to a paper in Nature Geoscience. Unfortunately, deadly tropical storms are only one way that the effects of climate change may harm human health, devastate livelihoods and kill people.

PHOTOS: Year's Biggest Storm Slams Philippines

Tiny bugs can kill as surely as gigantic storms can. The Asian tiger mosquito (Aedes albopictus) invaded the United States in the 1980s from its native range in Southeast Asia. The exceptionally aggressive mosquito can carry the deadly viruses that cause yellow fever, dengue and Chikungusya fever. Currently, 5 to 16 percent of the United States has a climate suitable to the Asian tiger mosquito, according to research published in PLOS ONE. That range could approach 50 percent within the next two decades as the nation warms.

However, Paul Reiter of the Centers for Disease Control argued that mosquito-borne diseases might not spread along with a warming climate, even if insect populations boom. In a paper published in Environmental Health Perspectives, Reiter noted that improved sanitation, eradication campaigns and other actions greatly reduced the incidence of malaria in such places as Rome and Washington D.C. Preventive measures could stop a climate-caused mosquito population boom from turning into a disease outbreak.

NEWS: Get Ready for Invading Asian Tiger Mosquitoes

Like dengue and yellow fever, the threat of Lyme disease could increase as climate change alters the biology of ticks. Lyme disease bacteria hitchhike inside deer ticks (Ixodes scapularis). Ticks pass through three stages in their development: larvae, nymph and adult. At each stage they take a drink of blood from an animal. If tick larvae suck blood from a Lyme disease-infected animal, the insect will then pass the disease on, potentially to a human, when it feeds as a nymph or adult.

Climate influences the severity of the Lyme disease strain those ticks carry, according to a study in Applied and Environmental Microbiology. In the northeastern United States, a long gap in the life cycle of ticks between spring and late summer results in a more debilitating form of the disease. As the world warms, the life cycle of ticks in the Midwest could become more like those insects in the Northeast and lead to higher rates of debilitating infections, warned the study's authors.

NEWS: How to Keep Ticks Off You

Some diseases won't need insects to boost their spread in a warmer world. Vibrio sp. bacteria, water-borne organisms responsible for diseases such as cholera and gastroenteritis, could be fertilized by the dust blowing off of parched deserts. Seafood, such as oysters, suck in Vibrio bacteria and can pass it on to people.

As climate change dries out West Africa and deserts expand, the wind may pick up more iron-rich dust and drop it into the oceans. Over the past 30 years, oceanic iron levels increased and seem likely to continue going up as Africa continues to bake and shed even more iron-rich dust, according to the National Oceanic and Atmospheric Administration (NOAA). That iron could fuel the growth of oceanic Vibrio bacteria in the ocean, which could subsequently infect seafood. At the 2011 meeting of the American Association for the Advancement of Science, University of Georgia researcher Erin Lipp presented her research on how iron pumps up Vibrio populations.

"Within 24 hours of mixing weathered desert dust from Morocco with seawater samples, we saw a 10-1000-fold growth in Vibrios, including one strain that could cause eye, ear, and open wound infections, and another strain that could cause cholera," said Erin Lipp of the University of Georgia in a NOAA news release.

PHOTOS: After the Dust Settles

Vibrio bacteria aren't alone in threatening to poison seafood as the climate changes. Toxic algae blooms, or red tides, caused by the species Alexandrium catenella could last longer in warmer oceans, according to researcher by NOAA and University of Washington biologists. That means more risk to humans from contaminated shellfish.

"Our projections indicate that by the end of the 21st century, blooms may begin up to two months earlier in the year and persist for one month later compared to the present-day time period of July to October," said NOAA researcher Stephanie Moore in a press release.

ANALYSIS: Red Tide Slaughtering Florida Manatees

Warmer air temperatures and increased rainfall can increase the number of salmonella, E. coli and other bacteria-related food poisoning cases because bacteria grow more rapidly in warm, moist environments. These diseases can cause gastrointestinal distress and, in severe cases, death. Climate change may increase the risk of the contamination of leafy green vegetables, such as lettuce, wrote the authors of a study published in the International Journal of Food Microbiology.

While increased rain may encourage dangerous bacteria to grow on foods, other areas may face the opposite problem as many arid areas get drier and hotter. As in the ongoing drought in Texas, sweltering, parched conditions wither agriculture and reduce drinking water supplies.

ANALYSIS: Compost Harbors Legionnaire's Disease Bacteria

Heat kills more than crops. Between 1999 and 2009, 7,223 heat-related deaths occurred in the United States, according to Centers of Disease Control statistics. Men accounted for nearly 5,000 of these deaths. Americans working in agriculture, logging, firefighting and construction face the greatest risk of heat-related injury or death, warns the National Institute for Occupational Safety and Health (NIOSH). Between 1992 and 2006, 432 workers died from heat-related causes in the United States, reported NIOSH.

Climate change will likely continue making heat waves more intense and dangerous for outdoor workers and other vulnerable groups. Americans over the age of 65 also face greater dangers from extreme heat waves. By the end of the 21st century, in just the city of Chicago, the number of deaths attributable to heat waves could rise by between 166 and 2,217 per year, depending on the severity of climatic warming, according to research published in Environmental Health Perspectives.

Rising temperatures and dry conditions also may allow increased numbers of more intense wildfires to run rampant, like the Yarnell fire that killed 19 firefighters earlier this year in Arizona.

PHOTOS: It's the Crazy-Extreme Weather Season

Allergies cost U.S. citizens $21 billion annually, according to the Environmental Protection Agency, and climate change could increase that figure, along with the number of itchy eyes and runny noses in America. Climate-related changes in ecosystems cause plants to produce pollen at different times and change when allergies hit. Warmer, wetter weather can increase the growth of plants and fungi that pump out the pollen responsible for many allergies. One greenhouse gas, carbon dioxide, boosts allergy-inducing plants in two ways. The gas not only increases the Earth's insulation, it also serves as a fertilizer for many plants.

The effects of climate change on the allergy season can already be felt. For example, ragweed season increased by up to 27 days in the past 15 years, especially at higher latitudes, according to USDA research published in the Proceedings of the National Academy of Science.

VIDEO: We're Crazy Close to a Cure for Allergies

Global warming seems to have set its sights on human lungs. Besides increased allergies, the Environmental Protection Agency warms that climate change will likely increase levels of ground-level ozone because warm, stagnant air facilitates the formation of ozone from other pollutants. Ozone also forms a component of smog.

Unlike its ultraviolet radiation-blocking brothers in the upper atmosphere, ground-level ozone does nothing to help humans. Breathing in ozone damages the lungs and can increase symptoms of asthma and other diseases. Even if ozone pollution levels remain steady until 2050, climate warming could increase the number of Red Ozone Alert Days (when the air is unhealthy for everyone) by 68 percent in the 50 largest eastern U.S. cities, according to the EPA.

ANALYSIS: US Parks Accidentally Fertilized By Air Pollution

One major source of bacterial contamination of food and water supplies comes from human and animal feces. After heavy rains and flooding, sewage and livestock wastes can overflow and spread filth and disease. For example, Sandra McLellan and her colleagues at the University of Wisconsin consulted climate models and predicted that spring rains in Wisconsin will probably increase over the next 50 years.

Wisconsin's sewer systems may not be able to handle that much foul water. Under worst case climate change scenarios, the volume of overflows may increase by 20 percent. Those overflows will last longer than they do now as antiquated drainage systems struggle to deal with the changing climate.

"Hundreds of millions of dollars are spent on urban infrastructure, and these investments need to be directed to problems that have the largest impact on our water quality," said McLellan in a press release. "Our research can shed light on this dilemma for cities with aging sewer systems throughout the Great Lakes and even around the world."

Top 10 Most Polluted Places on the Planet

Singer Edwin Starr might have asked, "Warming, what is it good for?" Absolutely nothing, just like war, he might have said. Natural climatic variations correlated to war and famine in pre-industrial Europe, according to research published in the Proceedings of the National Academy of Sciences. A study in the journal Nature examined more recent connections between climate fluctuations and conflict. For example, in 1982, a severe El Niño dried out the highlands of Peru and destroyed crops. That same year, attacks by the Sendero Luminoso, or Shining Path, guerrilla revolutionary movement escalated into civil war. During the 1997 El Niño, Congo, Eritrea, Indonesia, and Rwanda plunged into deadly turmoil.

The United States' Department of Defense's Defense Science Board (DSB) published a report calling for more information about how climate change could influence global security.

"Changes in climate patterns and their impact on the physical environment can create profound effects on populations in parts of the world and present new challenges to global security and stability," wrote Defense Science Board co-chairs, Larry Welch and Willian Howard in a letter preceding the DSB report,">Trends and Implications of Climate Change for National and International Security. "Failure to anticipate and mitigate these changes increases the threat of more failed states with the instabilities and potential for conflict inherent in such failures."

ANALYSIS: Climate Change Tied to a Violent Future