Global warming often seems distant and abstract, especially things like shrinking sea ice. But a turbulent climate also poses lots of relatable risks to human health, from allergies and asthma to algae blooms and animal-born diseases. And according to George Luber, chief of climate research at the U.S. Centers for Disease Control and Prevention, these are the risks that need public attention — even if it means less publicity for polar bears.

"We need to reframe the issue of climate change," Luber told an audience in Atlanta last week. "It's not just about polar bears, penguins and plants. It's about people."

Almost every angle of climate change eventually affects human health, even faraway ice loss. But certain changes have a more immediate impact on people, from heat stroke to less direct scourges like malnutrition or malaria. Publicizing these public health risks can not only convey the urgency of climate change to a wider swath of people, Luber says, but it can foster more targeted, localized plans for adapting to a warmer world.

As the CDC's associate director for climate change, Luber is in charge of a monumental task: preparing 314 million Americans for the health effects of climate change. "There's a pretty significant range of impacts to say the least, but the public health consequences have been largely unaddressed," he said July 12 at a roundtable discussion hosted by Southface, an Atlanta-based sustainability organization. "My little group at CDC represents the only federal program on the public health effects of climate change."

George Luber

CDC's George Luber speaks at the Sustainable Atlanta Roundtable on July 12. (Photo: Russell McLendon)

While global warming is a planetary problem, Luber stresses the importance of avoiding boilerplate adaptation strategies. "Climate change is not happening equally around the world. Any adaptation plan has to be as local as possible," he says.

That means different approaches based not just on latitude and elevation, but also on population density. "Cities and climate are co-evolving in ways that put more populations at risk," he adds. "There are multiple stressors: Humans are transitioning from a rural to an urban species, the world median age is increasing, and we live in increasingly urban environments with engineered structures that lead to the 'urban heat island.'"

Europe's 2003 heat wave was one of the first big wakeup calls about climate change and public health, Luber says, with a death toll somewhere between 30,000 and 70,000 people. But heat is only part of the problem for big cities; rising temperatures can worsen already-dismal air quality, for example, by increasing the number of high-ozone days. "Climate change is not acting in a vacuum," Luber says.

Here are a few examples of the various ways climate change threatens public health:

Wild weather

The most obvious effect of global warming is warmth, which can trigger health problems from mild heat rash to fatal heat stroke. It can also aggravate chronic conditions like cardiovascular or respiratory disease; ground-level ozone, for instance, causes direct lung injury while also raising the severity of long-term illnesses like asthma and COPD.

According to the U.N. Intergovernmental Panel on Climate Change — for which Luber is a lead author — there's a 90 percent probability that heat waves will be even more intense and frequent over the next century. Cities will likely bear the brunt of this heat, boosting demand for electricity that's still widely generated from fossil fuels, thus further fueling climate change and producing more airborne particulates that aggravate airways.

The IPCC says climate change is causing "unprecedented extreme weather," and recent events like Superstorm Sandy and historic wildfires have given form to this warning. Because heat drives evaporation, the sky is becoming more saturated overall, leading to stronger storms in some places and longer, drier droughts in others. While the former leads to flooding and wind damage, the latter spurs more wildfires in arid climates like the U.S. West, where fire season has grown 78 days longer since 1970.

Luber says the next IPCC report will confirm that climate change favors intense hurricanes, which, combined with rising sea levels, is terrible news for coastal U.S. cities. It's even worse in many developing nations, he adds, since big, dense slums tend to occupy flood-prone areas shunned by wealthier developments. Droughts and fires are also deadly far beyond the front lines, he adds, thanks to mobile threats like dust and smoke. During the 2009 Australian brushfires, for example, overall human mortality rose 5 percent.

Allergies and illnesses

On top of chemicals and particulates, climate change can also plague our airways by raising pollen counts. Excess carbon dioxide boosts plant growth, and the multitude of CO2 sources in cities — namely cars, trucks and buses — means urban allergens are especially worrisome. Hardy pollen-producing plants like ragweed are expected to fluorish in warmer cities, and researchers predict pollen counts will double within 30 years.

Other nuisance plants are also poised to thrive — poison ivy, for one, enjoys greater CO2 stimulation than most other woody species. That means faster growth and more skin-irritating urushiol, Luber says. "So we've got super poison ivy to look forward to, too."

That pales in comparison to some other warming-enabled diseases, though, including many spread by blood-sucking insects. Rising temperatures are helping mosquitoes expand their ranges to higher latitudes and elevations, Luber says, raising the risk that mosquito-born diseases like dengue fever, West Nile virus or chikungunya will also invade previously uninfected areas. But while mosquitoes "get all the attention," he says, they're far from the only disease-carrying interloper that stands to benefit from global warming.

Ticks are already spreading Lyme disease deeper into the U.S. Northeast and Midwest, according to CDC data, thanks to a mix of rising heat, plentiful deer and plentiful people. The tropical fungus Cryptococcus gattii has also begun infecting people in temperate places like British Columbia and the U.S. Northwest, prompting the CDC to study the role of climate change. Other emerging disease threats include the algae that cause red tide and ciguatera fish poisoning, Luber says, both of which are expanding north from the tropics.

Food security

Droughts and floods have already wreaked havoc with U.S. agriculture in recent years, but Luber warns the problem is even worse in developing nations, where fast-growing populations often rely on rainwater for irrigation. And while higher CO2 levels boost plant growth, that isn't the silver lining of climate change it might seem to be. Aside from promoting heat, storms and droughts that can decimate entire harvests, elevated CO2 level reduce the protein concentration of food crops, making them less nutritous.

According to an analysis published in 2008, wheat and rice lose about 10 percent of their protein concentration under elevated CO2, while potatoes and barley can lose up to 15 percent. Another study on several cereal grains found a 10 percent drop in protein.

"So in a world of 7 billion people, we'll have 10 percent less nutritious food," Luber says. "We can adapt out of weather, out of sea-level rise, but can we adapt out of CO2?"

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As the head of the CDC's climate change program, Luber got to offer input for President Obama's recently unveiled climate plan. Beyond the big focal points of curbing carbon emissions and boosting clean energy, he says he's relieved Obama also focused on localized adaptation plans. CO2 stays in the sky for centuries, and although U.S. emissions have fallen lately, they're still rising in many developing nations. Climate change will thus linger for generations to come, and it will manifest itself differently everywhere.

"We must understand local vulnerabilities," Luber says. "I don't think there's an area in this country, or the world, that's not affected by climate change."

For more about the public health effects of global warming, see this guide from the CDC.

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