Importance Health is inextricably linked to climate change. It is important for clinicians to understand this relationship in order to discuss associated health risks with their patients and to inform public policy. Objectives To provide new US-based temperature projections from downscaled climate modeling and to review recent studies on health risks related to climate change and the cobenefits of efforts to mitigate greenhouse gas emissions. Data Sources, Study Selection, and Data Synthesis We searched PubMed and Google Scholar from 2009 to 2014 for articles related to climate change and health, focused on governmental reports, predictive models, and empirical epidemiological studies. Of the more than 250 abstracts reviewed, 56 articles were selected. In addition, we analyzed climate data averaged over 13 climate models and based future projections on downscaled probability distributions of the daily maximum temperature for 2046-2065. We also compared maximum daily 8-hour average ozone with air temperature data taken from the National Oceanic and Atmospheric Administration, National Climate Data Center. Results By 2050, many US cities may experience more frequent extreme heat days. For example, New York and Milwaukee may have 3 times their current average number of days hotter than 32°C (90°F). High temperatures are also strongly associated with ozone exceedance days, for example, in Chicago, Illinois. The adverse health aspects related to climate change may include heat-related disorders, such as heat stress and economic consequences of reduced work capacity; respiratory disorders, including those exacerbated by air pollution and aeroallergens, such as asthma; infectious diseases, including vectorborne diseases and waterborne diseases, such as childhood gastrointestinal diseases; food insecurity, including reduced crop yields and an increase in plant diseases; and mental health disorders, such as posttraumatic stress disorder and depression, that are associated with natural disasters. Substantial health and economic cobenefits could be associated with reductions in fossil fuel combustion. For example, greenhouse gas emission policies may yield net economic benefit, with health benefits from air quality improvements potentially offsetting the cost of US and international carbon policies. Conclusions and Relevance Evidence over the past 20 years indicates that climate change can be associated with adverse health outcomes. Health care professionals have an important role in understanding and communicating the related potential health concerns and the cobenefits from policies to reduce greenhouse gas emissions.

To examine the impact of tropical rain-forest destruction on malaria, we conducted a year-long study of the rates at which the primary malaria vector in the Amazon, Anopheles darlingi, fed on humans in areas with varying degrees of ecological alteration in the Peruvian Amazon. Mosquitoes were collected by human biting catches along the Iquitos-Nauta road at sites selected for type of vegetation and controlled for human presence. Deforested sites had an A. darlingi biting rate that was more than 278 times higher than the rate determined for areas that were predominantly forested. Our results indicate that A. darlingi displays significantly increased human-biting activity in areas that have undergone deforestation and development associated with road development.

An estimated 700,000 to 2.7 million people die of malaria each year, and 75% of those are African children (www.cdc.gov/malaria). Recent resurgence in the East African highlands involves multiple factors, from climate and land use change to drug resistance, variable disease control efforts, and other sociodemographic factors (1). But malaria is an extremely climate-sensitive tropical disease, making the assessment of potential change in risk due to past and projected warming trends one of the most important climate change/health questions to resolve. Pascual et al . (2) now provide important new insights toward answering this malaria/climate question in their article in this issue of PNAS. Pascual’s research team used a de-trended time series of temperature and documented a warming trend in the East African highlands from 1950 to 2002, concomitant with increases in malaria incidence. Moreover, their findings confirm the importance of the well recognized nonlinear and threshold responses of malaria (a biological system) to the effect of regional temperature change (Fig. 1). For example, showing that the biological response of mosquito populations to warming can be more than an order of magnitude larger than the measured change in temperature represents a stunning finding, critical in advancing risk assessment of climate change impacts. Those who argue that we need not worry about small shifts in temperature should … *To whom correspondence should be addressed. E-mail: patz{at}wisc.edu

Large-scale anthropogenic changes to the natural environment, including land-use change, climate change, and the deterioration of ecosystem services, are all accelerating. These changes are interacting to generate five major emerging public health threats that endanger the health and well-being of hundreds of millions of people. These threats include increasing exposure to infectious disease, water scarcity, food scarcity, natural disasters, and population displacement. Taken together, they may represent the greatest public health challenge humanity has faced. There is an urgent need to improve our understanding of the dynamics of each of these threats: the complex interplay of factors that generate them, the characteristics of populations that make them particularly vulnerable, and the identification of which populations are at greatest risk from each of these threats. Such improved understanding would be the basis for stepped-up efforts at modeling and mapping global vulnerability to each of these threats. It would also help natural resource managers and policy makers to estimate the health impacts associated with their decisions and would allow aid organizations to target their resources more effectively.