People and Global Change: Hazards, Vulnerability, and Socioeconomic Impacts

Course Logistics and Academic Announcements The course schedule for late April and early May 2026 includes several critical deadlines and opportunities. On 29 April 2026, it was announced that Homework 10 (HW10), covering Module 10: Biological Impacts of Climate Change, is due by Friday, May 1st. Quiz 12, covering all of Lecture 10 and the associated video lecture, was administered on April 29th. The final quiz of the semester is scheduled for Monday, May 4th, covering Lecture 11: People and Climate Change. Students have an opportunity for extra credit on the final exam by completing the Student Opinion Survey via the ODU technology services portal. If the class reaches a $75\%$ response rate by the start of class on Friday, May 1st, every student will receive a $+5$ point bonus on the final exam. As of April 29th, the response rate was $16\%$, which increased to $34\%$ by May 1st. Final exam study materials have been posted to CANVAS. # Ethical Dimensions and Global Disparity in Climate Impact A central theme of global change is the disproportionate impact on the developing world. Vulnerable populations in developing nations often face the most severe consequences of rapid global change despite having the smallest ecological footprints. Carbon dioxide ($CO_2$) emissions from industrial processes are highest in North and Central America, Europe, and Asia, while regions like Africa, South America, and Oceania contribute significantly less but remain highly susceptible to damage. This creates a significant ethical issue regarding responsibility versus impact. # The Framework of Hazard, Vulnerability, and Risk The study of how climate change affects humanity relies on the metrics of hazards, vulnerability, and risk. A hazard is defined as any event or condition that causes injury, disease, or death to humans; damage to personal or public property; or the deterioration and destruction of environmental components. Hazards are categorized into four types: Physical, Biological, Cultural, and Chemical. These categories are not mutually exclusive. Vulnerability is determined by three factors: adaptability, exposure, and sensitivity. The relationship between these concepts is expressed through the formula: $\text{Risk} = \text{Hazard} \times \text{Vulnerability}$. # Determinants of Vulnerability and Adaptive Capacity Adaptability refers to the capability of a society to adjust to changes and is a function of wealth, technology, education, institutional strength, information availability, infrastructure, and social capital. Social capital is defined as a set of shared values that enables individuals to work together in a group to effectively achieve common purposes and live harmoniously. Having the capacity to adapt does not guarantee that it will be utilized effectively; the Great Galveston Sea Wall is an example of physical adaptation infrastructure. Exposure relates to the physical presence of threats like hurricanes, tornadoes, droughts, and floods. Sensitivity identifies which specific populations, such as the poor or elderly, will be most acutely affected by a hazard. # Case Study 1: Freshwater Stress and Regional Scarcity Global change has significantly increased freshwater stress, measured as the ratio of total water withdrawals to the total renewable supply. Stress levels are categorized as Low ($< 10\%$), Low to Medium ($10 - 20\%$), Medium to High ($20 - 40\%$), High ($40 - 80\%$), and Extremely High ($> 80\%$). In North Africa, projections for the year 2100 indicate a temperature increase of $3.5 - 4.5\,^\circ\text{F}$ and a decrease in precipitation of up to $40\%$ in certain areas. This region, already naturally dry and experiencing rapid population growth, faces severe water shortages and drought risks. # Case Study 2: Agriculture, Food Security, and Famine Climate change is projected to increase the prevalence of famine due to the combination of population growth, water scarcity, and reduced food yields. In India, agriculture is a vital sector; while it accounted for $42\%$ of GDP in 1980, it dropped to $14\%$ by 2010, yet it still supports a dependent population of $70\%$. Most Indian farms are small, ranging from $1$ to $5\,\text{ha}$, making them sensitive to change. With a warming of $3.5 - 4.5\,^\circ\text{F}$ and a $-20\%$ drop in precipitation, rice yields in India could fall by $15\%$ to $42\%$, while wheat yields could drop by $25\%$ to $55\%$. Such climate shifts could reduce net farm revenues by $9\%$ to $25\%$. On a global scale, cereal crop and livestock productivity are expected to decrease in most tropical and subtropical regions. # Case Study 3: Sea Level Rise and Coastal Displacement According to IPCC predictions, sea levels are projected to rise between $0.5$ and $1.2\,\text{m}$ ($1.6$ and $3.9\,\text{feet}$) by 2100, depending on the emission scenario. On the Indian subcontinent, the impacts will be catastrophic. In Bangladesh, this rise is expected to displace $13\,\text{million}$ people and result in the loss of $16\%$ of national rice production. In India, an estimated $7\,\text{million}$ people could be displaced at a cost of approximately $\$230\,\text{billion}$. This would include the inundation of $1700\,km^2$ ($1050\,\text{miles}$) of agricultural land and require the construction of $4000\,km$ ($2500\,\text{miles}$) of dikes and sea walls. Additionally, $576\,km^2$ ($350\,\text{miles}$) of land and $4200\,km$ ($2600\,\text{miles}$) of roads would be submerged. # Case Study 4: Disease Proliferation and Human Health Challenges Global warming facilitates the spread of tropical-borne diseases. Approximately $40\%$ of the world currently lives in malaria-prevalent areas. Malaria kills roughly one person every minute, and $76\%$ of its victims are children under the age of 5. By 2050, the distribution of the primary malaria agent (the falciparum Malaria parasite) is projected to extend into new regions based on the HadCM2 high-scenario experiment. Other anticipated health effects include virtually certain increases in heat-related mortality (especially among the young and elderly) and a decrease in cold-related deaths. Frequent flooding is very likely to increase injuries and skin/respiratory diseases, while frequent droughts are likely to cause malnutrition and food-borne illnesses. Increased cyclone activity and high-sea-level events are likely to lead to post-traumatic stress disorder (PTSD) and deaths during migration. # Socioeconomic Impacts and Climate Management Even minor temperature rises can trigger food price spikes as global demand outpaces supply, lowering the incomes of vulnerable populations and increasing the number of people at risk of hunger. This creates the threat of mass starvation in fragile societies and the rise of climate refugees. Management of these risks involves Mitigation and Adaptation. An economic model of potential damage over the next several decades estimates potential climate change damage at $\$20,000,000,000$. With a $\$2,000,000,000$ investment in reduction (adaptation/mitigation), the damage could be reduced by $\$5,000,000,000$, resulting in a net damage of $\$17,000,000,000$. # Risks Associated with a $2\,^\circ\text{C}$ Increase A warming of $2\,^\circ\text{C}$ above pre-industrial levels is considered a critical threshold. At this level, it is estimated that $3.5\,\text{billion}$ people will be at risk of water shortages, hundreds of millions at risk of malaria, and tens of millions at risk of hunger. The risk of coastal flooding will also rise sharply. This level of warming risks major ice sheet responses that could commit the planet to several meters of sea level rise in the long term, and it threatens major ecosystems from the poles to the tropics, with the economic costs of forest and species loss falling most heavily on the poor. Current data shows the 1961-1990 average temperature was $0.32\,^\circ\text{C}$ above pre-industrial levels (1861-1890).