This dissertation comprises three chapters that empirically quantify the externalities of climate change and the effectiveness of water quality policy. The areas of focus include the effect of temperature on mortality rates and the impact of a coastal water quality policy in South Korea. Furthermore, I seek to find economic opportunities under climate change in New England’s coastal communities through value-added seafood products. The first chapter, titled “The Impact of Temperature on Mortality in South Korea,” documents the temperature-mortality relationship in South Korea and examines the potential for electricity to mitigate harm. The study combines county-level daily weather data, monthly mortality rates, and residential electricity consumption from 2016 to 2019. The temperature-mortality relationship demonstrates larger increases in mortality at extreme temperatures, especially at colder temperatures and among the elderly population. Electricity use modestly mitigates deaths at higher temperature levels. The second chapter, titled “The Impact of a Coastal Water Quality Policy in South Korea: Evidence from the Total Pollution Load Management Program,” examines the impact of the Total Pollutant Load Management (TPLM) program on coastal water quality in South Korea. The study utilizes comprehensive data from 2011 to 2021 and applies a difference-in-differences model. The empirical model accounts for the program’s staggered introduction and the overall evaluation frequency changes in 2016. The study found that the TMDL impacts are mixed: certain targeted measures improve, whereas others degrade. As for the effect of changes in evaluation frequency, the study found evidence of water quality improvement after accounting for violations in parallel pre-trend. The third chapter, titled “Are Seafood Consumers Willing to Pay to Support Sustainable Coastal Economies?”, investigates consumer preferences for value-added seafood dishes in New England. Climate change in the Gulf of Maine affects the sustainability of the marine environment and coastal economies. Providing information about the local environment and economic benefits of seafood consumption can promote sustainable coastal economies. The study applies a choice experiment survey and a mixed logit model to estimate marginal willingness to pay for haddock, oyster, and plant-based shrimp offering these benefits. Findings indicate that consumers place high values on marine population conservation, year-round job, and locally sourced seafood. Additionally, individuals familiar with the blue economy concept tend to place greater value on these products.