Climate Change

Glacial CalvingClimate change, caused by increasing atmospheric concentrations of greenhouse gases, is driven by human activity. Anthropogenic emissions of carbon dioxide, methane, nitrous oxide, and black carbon are primarily responsible for the changing climate. Burning fossil fuels and clearing natural habitats for human use produce the majority of these emissions. Climate change continues to cause glacial melting in Greenland and the Antarctic, rising sea levels, increases in global mean surface temperatures, increases in extreme weather events, and changes in the abundance, distribution, and composition of species. Climate change and the above ecosystem transformations are inextricably connected; as a result, these changes and impacts mutually exacerbate each other.

Learning Objectives

  • L1: Summarize climatic changes over time, highlighting specific eras in human history.
  • L2: Describe and discuss the anthropogenic drivers of climate change.
  • L3: Consider strategies for climatic adaptation and mitigation with a focus on human health.
  • L4: Critically evaluate the purpose and effectiveness of recent global climate change policies and events, considering the roles of key stakeholders.


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Smith KR, Woodward A, Lemke B, Otto M, Chang CJ, Mance AA, Balmes J, Kjellstrom T. The last Summer Olympics? Climate change, health, and work outdoors. The Lancet [Internet]. 2016;388 (10045) :642-644. Publisher's VersionAbstract

Climate change threatens human health in many ways, through heat waves, extreme weather events, and shifts in disease vectors, as well as economic and social stresses on populations living in or trying to escape areas affected by seawater intrusion, drought, lower agricultural productivity, and floods.1 In the short term, most of these impacts could be substantially ameliorated by actions to reduce background disease risks and other known causes of vulnerability. The world beyond 2050 poses increasingly difficult challenges, not only because of the inherent uncertainties in long-term predictions, but because the extent and speed of change might exceed society's ability to adapt.

Orr JC, Fabry VJ, Aumont O, Bopp L, Doney SC, Feely RA, Gnanadesikan A, Gruber N, Ishida A, Joos F, et al. Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms. Nature [Internet]. 2005;437 :681-686. Publisher's VersionAbstract

Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms—such as corals and some plankton—will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean–carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.

Fabry VJ, Seibel BA, Feely RA, Orr JC. Impacts on ocean acidification on marine fauna and ecosystem processes. ICES Journal of Marine Science [Internet]. 2008;65 (3) :414-432. Publisher's VersionAbstract

Oceanic uptake of anthropogenic carbon dioxide (CO2) is altering the seawater chemistry of the world’s oceans with consequences for marine biota. Elevated partial pressure of CO2 (pCO2) is causing the calcium carbonate saturation horizon to shoal in many regions, particularly in high latitudes and regions that intersect with pronounced hypoxic zones. The ability of marine animals, most importantly pteropod molluscs, foraminifera, and some benthic invertebrates, to produce calcareous skeletal structures is directly affected by seawater CO2 chemistry. CO2influences the physiology of marine organisms as well through acid-base imbalance and reduced oxygen transport capacity. The few studies at relevant pCO2 levels impede our ability to predict future impacts on foodweb dynamics and other ecosystem processes. Here we present new observations, review available data, and identify priorities for future research, based on regions, ecosystems, taxa, and physiological processes believed to be most vulnerable to ocean acidification. We conclude that ocean acidification and the synergistic impacts of other anthropogenic stressors provide great potential for widespread changes to marine ecosystems.

Branch TA, DeJoseph BM, Ray LJ, Wagner CA. Impacts of ocean acidification on marine seafood. Trends in Ecology and Evolution [Internet]. 2013;28 (3) :178-186. Publisher's VersionAbstract

Ocean acidification is a series of chemical reactions due to increased CO2 emissions. The resulting lower pH impairs the senses of reef fishes and reduces their survival, and might similarly impact commercially targeted fishes that produce most of the seafood eaten by humans. Shelled molluscs will also be negatively affected, whereas cephalopods and crustaceans will remain largely unscathed. Habitat changes will reduce seafood production from coral reefs, but increase production from seagrass and seaweed. Overall effects of ocean acidification on primary productivity and, hence, on food webs will result in hard-to-predict winners and losers. Although adaptation, parental effects, and evolution can mitigate some effects of ocean acidification, future seafood platters will look rather different unless CO2 emissions are curbed.


Ainsworth EA, Rogers A, Blum H, Nosberger J, Long SP. Variation in acclimation of photosynthesis in Trifolium repens after eight years of exposure to Free Air CO 2 Enrichment (FACE). Journal of Experimental Botany [Internet]. 2003;54 :2769-2774. Publisher's VersionAbstract

The initial stimulation of photosynthesis observed on elevation of [CO2] in grasslands has been predicted to be a transient phenomenon constrained by the loss of photosynthetic capacity due to other limitations, notably nutrients and sinks for carbohydrates. Legumes might be expected partially to escape these feedbacks through symbiotic N2 fixation. The Free-Air Carbon dioxide Enrichment (FACE) experiment at Eschikon, Switzerland, has been the longest running investigation of the effects of open-air elevation of [CO2] on vegetation. The prediction of a long-term loss of photosynthetic capacity was tested by analysing photosynthesis in Trifolium repens L. (cv. Milkanova) in the spring and autumn of the eighth, ninth and tenth years of treatment. A high and low N treatment also allowed a test of the significance of exogenous N-supply in maintaining a stimulation of photosynthetic capacity in the long-term. Prior work in this Free Air CO2 Enrichment (FACE) experiment has revealed that elevated [CO2] increased both vegetative and reproductive growth of T. repens independent of N treatment. It is shown here that the photosynthetic response of T. repens was also independent of N fertilization under both current ambient and elevated (600 micro mol mol-1) [CO2]. There was a strong effect of season on photosynthesis, with light-saturated rates (Asat) 37% higher in spring than in autumn. Higher Asat in the spring was supported by higher maximum Rubisco carboxylation rates (Vc,max) and maximum rates of electron transport (Jmax) contributing to RuBP regeneration. Elevated [CO2] increased Asat by 37% when averaged across all measurement periods and both N fertilization levels, and decreased stomatal conductance by 25%. In spring, there was no effect of elevated [CO2] on photosynthetic capacity of leaves, but in autumn both Vc,max and Jmax were reduced by approximately 20% in elevated [CO2]. The results show that acclimation of photosynthetic capacity can occur in a nitrogen-fixing species, in the field where there are no artificial restrictions on sink capacity. However, even with acclimation there was a highly significant increase in photosynthesis at elevated [CO2].

Eakin H, Luers AL. Assessing the Vulnerability of Social-Environmental Systems. Annual Review of Environment and Resources [Internet]. 2006;31 :365-394. Publisher's VersionAbstract

In this review, we highlight new insights into the conceptualization of the vulnerability of social-environmental systems and identify critical points of convergence of what otherwise might be characterized as disparate fields of research. We argue that a diversity of approaches to studying vulnerability is necessary in order to address the full complexity of the concept and that the approaches are in large part complementary. An emerging consensus on the issues of critical importance to vulnerability reduction—including concerns of equity and social justice—and growing synergy among conceptual frameworks promise even greater relevancy and utility for decision makers in the near future. We synthesize the current literature with an outline of core assessment components and key questions to guide the trajectory of future research.

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