Scientific consensus indicates that changes in climate will have substantial effects throughout Earth, ranging from higher surface temperatures and rising sea levels to an increasing number of severe weather events. Continuing the theme begun in the keynote address, George Luber, an epidemiologist and the associate director for global climate change at the National Center for Environmental Health of the Centers for Disease Control and Prevention, described how those changes are expected to cause a wide array of direct and indirect human health consequences.

Luber quoted the 2007 report of the Intergovernmental Panel on Climate Change (IPCC), which indicated that global warming is already happening, that physical and biological systems on all continents and oceans are already affected by climate changes, and that we are already committed to more warming over the next few decades because our choices about emissions affect the longer term more and more. Global temperatures and sea levels have both risen unequivocally over the last 150 years, while the polar ice cap has shrunk. None of those observed trends, says Luber, can be reproduced without the effects of human-made drivers, such as increased concentrations of greenhouse gases and tropospheric aerosols.

The 2007 IPCC report also predicted more than a 90% probability of more intense and frequent heat waves and heavy precipitation events and more than a 66% probability that tropical cyclones will become more intense, that more areas will be affected by drought, and that the incidence of extremely high sea levels will increase. Addressing the health effects of those changes, said Luber, will require a multipronged approach focusing on such issues as environmental justice, the need for effective communication of health dangers to the public, and consideration of complex ecosystem interactions resulting from climate change.

Cities and climate are coevolving in a manner that will place more populations at risk, Luber stated. Today, more than half the world’s population lives in cities, up from 30% in 1950. By 2100, there will be 100 million more people over 65 years old than there were in 2000. That is important because cities are known to intensify exposures through urban heat islands and stagnant air masses, which can add 7°F to 12°F to the average late-afternoon temperature and increase ozone concentrations. The increase in CO2 can also lead to increased pollen counts and a longer growing season for urban allergens, such as ragweed and poison ivy. Other potential health effects of climate change are heat stress and cardiovascular failure; increases in vectorborne and waterborne diseases, such as malaria, dengue, and cholera; malnutrition; harmful algal blooms; anxiety, depression, and posttraumatic stress; and forced migration of and civil conflict involving environmental refugees.

Despite the existing breadth of organizations and sectors that have initiatives on climate change and despite the likelihood of health consequences of climate change, Luber believes that the public-health effects of climate change remain largely unaddressed. He provided three guiding principles, both practical and ethical, that should be used to move toward a publichealth framework for addressing climate change: co-benefits and synergies, environmental justice, and communication.

Efforts to mitigate or adapt to the effects of climate change often yield other health benefits, both direct and indirect, said Luber. For example, decreased vehicular traffic results in fewer car crashes and less air pollution, and the use of locally grown food results in lower pesticide loads and fuel needs. Environmental justice is important because climate change will disproportionately threaten some populations, especially poor people and members of ethnic and racial minorities. And communication is key—affecting behavior change to mitigate and adapt to the effects of climate change will require a fundamental shift in communication strategies. Health marketing provides one potential framework for a communication shift. Research has shown that messages directed at specific “market segments” and appealing to values and selfinterest can be effective.

Luber concluded by stating that climate change is now a mainstream scientific issue but that it must also be framed as a humanwelfare and public-health issue. The costs of not taking action would be high.