本文以 Desmet et al. (2021) 的動態空間模型與設定為基礎，分析氣候變遷下海平面上升對全球與各國之長期影響。模型將全球劃分為多個地理網格，並納入家戶效用、人口遷移、廠商創新、貿易成本與技術演進等機制，使海平面上升所造成的土地損失能進一步影響人口與經濟活動的空間配置。
本文主要進行三項分析。第一，本文重現 RCP 4.5 情境下海平面上升對全球經濟的基準影響。結果顯示，全球實質 GDP 損失並非隨時間單調增加，而是呈現先上升後下降的趨勢。此結果表示，海平面上升初期會破壞既有沿海經濟聚落，但隨著人口與經濟活動重新配置，長期損失可被部分緩和。
第二，本文比較國家層級的 GDP、福利、人口與土地損失差異。結果顯示，海平面上升對各國影響具有高度異質性，全球平均損失並不代表所有國家皆受到相同程度衝擊。越南、孟加拉與泰國在經濟、福利或人口損失上較為明顯；同時，土地損失比例與經濟損害並非一對一對應，因為受淹沒土地所承載的人口密度、經濟活動、生產力與地點效用不同，會使相同程度的土地損失產生不同的經濟結果。
第三，本文設計沿海城市保護情境，假設特定高風險城市或地區透過海堤等防護措施避免土地淹沒，並比較有無保護下的經濟結果。模擬結果顯示，保護達卡與吉大港、曼谷、胡志明市與上海等地，對降低其所屬國家的 GDP、福利與人口損失具有較明顯效果。進一步納入海岸線長度與保護成本後，曼谷、胡志明市、達卡與吉大港，以及上海具有較高的相對保護效益。

This study builds on the dynamic spatial model of Desmet et al. (2021) to examine the long-term impacts of sea level rise on the global economy and individual countries under climate change. The model divides the world into geographic grid cells and incorporates household utility, population migration, firm innovation, trade costs, and technological change, allowing land loss from sea level rise to affect the spatial allocation of population and economic activity.
This study conducts three main analyses. First, it replicates the benchmark global impact of sea level rise under the RCP 4.5 scenario. The results show that global real GDP losses do not increase monotonically over time, but rise initially and decline later, suggesting that long-run population and economic reallocation can partially mitigate early coastal losses.
Second, this study compares country-level losses in GDP, welfare, population, and land. The results indicate strong cross-country heterogeneity. Vietnam, Bangladesh, and Thailand experience relatively large losses, while land loss does not necessarily translate into proportional economic damage because flooded areas differ in population density, productivity, economic activity, and location-specific utility.
Third, this study designs coastal city protection scenarios, assuming that selected high-risk cities are protected from inundation through measures such as seawalls. The results show that protecting Dhaka and Chittagong, Bangkok, Ho Chi Minh City, and Shanghai can reduce national GDP, welfare, and population losses. After considering coastline length and protection costs, these cities also show relatively high protection benefits.

Conte, B., Desmet, K., Nagy, D. K., & Rossi-Hansberg, E. (2021). Local sectoral specialization in a warming world. Journal of Economic Geography, 21(4), 493-530. https://doi.org/10.1093/jeg/lbab008
Copernicus Marine Service. (2025). Global ocean mean sea level time series and trend from observations reprocessing [Available at: https://data.marine.copernicus.eu/product/OMI_CLIMATE_SL_GLOBAL_area_averaged_anomalies/description]. https://doi.org/10.48670/moi-00237
Cruz, J.-L., & Rossi-Hansberg, E. (2024). The economic geography of global warming. The Review of Economic Studies, 91(2), 899-939.
Desmet, K., Kopp, R. E., Kulp, S. A., Nagy, D. K., Oppenheimer, M., Rossi-Hansberg, E., & Strauss, B. H. (2021). Evaluating the economic cost of coastal flooding. American Economic Journal: Macroeconomics, 13(2), 444-486. https://doi.org/10.1257/mac.20180366
Desmet, K., Nagy, D. K., & Rossi-Hansberg, E. (2018). The geography of development. Journal of Political Economy, 126(3), 903-983. https://doi.org/10.1086/697084
Diaz, D. B. (2016). Estimating global damages from sea level rise with the coastal impact and adaptation model (ciam). Climatic Change, 137(1-2), 143-156. https://doi.org/10.1007/s10584-016-1675-4
Eaton, J., & Kortum, S. (2002). Technology, geography, and trade. Econometrica, 70(5), 1741-1779. https://doi.org/10.1111/1468-0262.00352
Hillen, M. M., Jonkman, S. N., Kanning, W., Kok, M., Geldenhuys, M. A., & Stive, M. J. F. (2010). Coastal defence cost estimates: Case study of the netherlands, new orleans and vietnam (tech. rep.). Delft University of Technology.
Hinkel, J., Lincke, D., Vafeidis, A. T., Perrette, M., Nicholls, R. J., Tol, R. S. J., Marzeion, B., Fettweis, X., Ionescu, C., & Levermann, A. (2014). Coastal flood damage and adaptation costs under 21st century sea-level rise. Proceedings of the National Academy of Sciences, 111(9), 3292-3297. https://doi.org/10.1073/pnas.1222469111
IPCC. (2019). Ipcc special report on the ocean and cryosphere in a changing climate. Intergovernmental Panel on Climate Change.
IPCC. (2021). Climate change 2021: The physical science basis. contribution of working group i to the sixth assessment report of the intergovernmental panel on climate change. Cambridge University Press. https://doi.org/10.1017/9781009157896
IPCC. (2022). Climate change 2022: Impacts, adaptation and vulnerability. contribution of working group ii to the sixth assessment report of the intergovernmental panel on climate change. Cambridge University Press. https://doi.org/10.1017/9781009325844
Kopp, R. E., Horton, R. M., Little, C. M., Mitrovica, J. X., Oppenheimer, M., Rasmussen, D. J., Strauss, B. H., & Tebaldi, C. (2014). Probabilistic 21st and 22nd century sea-level projections at a global network of tide-gauge sites. Earth's Future, 2(8), 383-406. https://doi.org/10.1002/2014EF000239
NASA Earth Observatory. (2021). Preparing for rising seas in the maldives [Available at: https://science.nasa.gov/earth/earth-observatory/preparing-for-rising-seas-in-the-maldives-148158/].
Natural Earth. (2024). Natural earth: Free vector and raster map data. Natural Earth.
Redding, S. J., & Rossi-Hansberg, E. (2017). Quantitative spatial economics. Annual Review of Economics, 9, 21-58. https://doi.org/10.1146/annurev-economics-063016-103713
Simonovska, I., & Waugh, M. E. (2014). The elasticity of trade: Estimates and evidence. Journal of International Economics, 92(1), 34-50. https://doi.org/10.1016/j.jinteco.2013.10.001
United Nations Framework Convention on Climate Change. (2015). Paris agreement. United Nations.
World Bank. (2021). International comparison program 2021: Price level index. World Bank.
World Bank. (2025a). Land area (sq. km), indicator ag.lnd.totl.k2 [Available at: https://databank.worldbank.org/source/world-development-indicators].
World Bank. (2025b). World development indicators: Gdp (current us$), indicator ny.gdp.mktp.cd [Available at: https://databank.worldbank.org/source/world-development-indicators].
Zabreyko, P. P., Koshelev, A. I., Krasnosel'skii, M. A., Mikhlin, S. G., Rakovshchik, L. S., & Stetsenko, V. Y. (1975). Integral equations: A reference text. Noordhoff International Publishing.