Five Feet High and Rising: Why Sea Level Rise Necessitates an Amendment to the United Nations Convention on the Law of the Sea

The Sea Level Rise Problem

Global warming is causing sea levels to rise at an alarmingly rapid rate.[1] Sea levels remained fairly stable for roughly 2000 years until the 20th century, when sea levels began gradually rising by an average of 0.06 inches per year alongside increasing global temperatures.[2] This rate of sea level rise roughly doubled in 1993 to 0.12 to 0.14 inches per year.[3] Between 1880 and 2022, global mean sea levels rose between eight to nine inches—between 2022 and 2100 it is estimated that global mean sea levels could rise from anywhere between one to six feet, largely contingent upon future greenhouse gas emissions and global warming trends.[4] A consequence of sea level rise is the legal uncertainty it poses to the application of the United Nations Convention on the Law of the Sea (UNCLOS).

UNCLOS and Looming Uncertainty

UNCLOS is a multilateral treaty that establishes the legal regime dealing with ocean use and maritime activities among states.[5] An important feature of UNCLOS is the establishment of several maritime zones that protrude off of the coastline of states.[6] The coastline is the starting point for measuring how far the maritime zones extend into the ocean and is determined by reference to a country’s “normal baseline,” which is defined as “the low-water line along the coast [of the State,] as marked on large-scale charts officially recognized by the coast State.”[7]

The first twelve nautical miles extending from a state’s normal baseline into the ocean are referred to as a state’s territorial sea.[8] The territorial sea functions as an extension of state sovereignty, and permits a state to exercise complete control over both the sky above, and the subsoil beneath, the territorial sea.[9] The first twenty-four nautical miles beyond a state’s baseline is its contiguous zone, over which a state may prevent and punish infringement of state law and regulation.[10] Other zones, like the exclusive economic zone and continental shelf, are also based on measurements derived from the normal baseline or territorial sea.[11]

The friction between UNCLOS and sea level rise lies in a state’s baseline being ambulatory, in that it could change over time depending upon where “the low water line along the coast” happens to be found.[12] Since the rights associated with the different UNCLOS zones are interwoven with state sovereignty and boundaries, fluctuation in baselines is a potential source of conflict as sea levels rise.[13]

A Path to Amending UNCLOS to Create Certainty

Several arguments have been put forward to create legal certainty around maintaining baselines in the face of sea level rise, which have turned on either interpreting already existing provisions within UNCLOS or establishing new customary international law around baselines.[14] However, the arguments around interpreting current UNCLOS provisions to address sea level rise and baselines are, at best, uncertain in their application to the issue.[15] Further, the consistent state practice and opinio juris required for establishing customary international law around respecting baselines in the face of sea level rise has not yet been well enough established to create a sense of certainty, despite attempts to the contrary.[16]

Another option to create legal certainty around sea level rise and baselines would be to amend UNCLOS to either include a provision directed towards sea level rise or to alter Article 5 to create a framework for freezing baselines at their current position. Articles 312 and 316 of UNCLOS address its amendment procedures.[17] Any State Party, after a period of ten years from the date of entry into the Convention, may propose an amendment and request a conference to consider the proposed amendment.[18] Then, the Secretary-General circulates the proposed amendment to all State Parties, and if half of the State Parties approve the request, then a conference is held to consider the amendment.[19] If ratification and accession is obtained by two-thirds of the State Parties, the amendment is entered into force, but only against those State Parties who provided ratification and accession.[20]

Amending UNCLOS is the surest way to address sea level rise and ambulatory baselines because it would create a concrete source of international law addressing the issue. While UNCLOS has never been amended, partly because other international organizations have stepped in to fill small gaps in its application,[21] there is obviously nothing precluding State Parties from doing so now. While some have said amendment to UNCLOS is not an effective solution to sea level rise because the amendment process is difficult to execute and could challenge the legitimacy of UNCLOS,[22] these arguments should not deter attempts at amendment. First, the amendment procedure being difficult should not discourage amendment because sea level rise poses a threat to the entire UNCLOS baseline framework, and even poses a threat to the survival of some states.[23] Such a serious issue should inspire action among State Parties. Second, amending UNCLOS would not undermine its legitimacy because international agreements are routinely amended.[24] The arguments against amendment are not strong enough to outweigh the greater certainty amending UNCLOS provides against changing baselines.

  1. See, e.g., Rebecca Lindsay, Climate Change: Global Sea Level, National Oceanic and Atmospheric Administration (Apr. 19, 2022),
  2. Climate Change Indicators: Sea Levels, Environmental Protection Agency (July 2022),,as%20the%20long%2Dterm%20trend.
  3. Id.
  4. Supra, note 1.
  5. United Nations Convention on the Law of the Sea, International Maritime Organization, (last visited Mar. 3, 2024).
  6. See U.N. Convention on the Law of the Sea, Parts II, V, and VI, Dec. 10, 1982, 1833 U.N.T.S. 397.
  7. Id. Part II, sec. 2, art. 5.
  8. Id. Part II, sec. 2, art. 3
  9. Id. Part II, sec. 1, art. 2
  10. Id. Part II, sec. 4, art. 33.
  11. Id. Parts V & VI, arts. 56–57 & 76.
  12. Davor Vidas & David Freestone, The Impacts of Sea Level Rise and the Law of the Sea Convention: Facilitating Legal Certainty and Stability of Maritime Zones and Boundaries, 99 Int’l L. Stud. Ser. US Naval War College 944, 945–946 (2022).
  13. Jin Zhang, On the Legal Implications of Sea Level Rise on Baselines and Its Countermeasures, China Oceans L. Rev. 142, 148–152 (2022).
  14. See id. at 152–159; see also Vincent P. Cogliati-Bantz, Sea-Level Rise and Coastal States’ Maritime Entitlements: A Cautious Approach, 7 J. Territorial & Mar. Stud. 86, 93–98 (2020).
  15. Zhang, supra note 14, at 153–156.
  16. See Cogliati-Bantz, supra note 14, at 94–95, 99 (describing attempts by states in the Pacific region to call for legal recognition of existing baselines, and why the burdens of establishing customary international law on the issue have not yet been satisfied).
  17. U.N. Convention on the Law of the Sea, Part XVII, arts. 312 & 316, Dec. 10, 1982, 1833 U.N.T.S. 397 (it is worth noting that there is a simplified amendment procedure contained in article 313, but under that framework if a single state objects to the proposed amendment, then the amendment is considered rejected—meaning the 313 amendment procedure would require unanimous consent of all state parties, and is thus extremely difficult, if not impossible, to use).
  18. Id. art. 312.
  19. Id. art. 312.
  20. Id. art 316.
  21. Chris Whomersley, How to Amend UNCLOS and Why It Has Never Been Done, 9 Korean J. Int’l & Comp. L. 72, 81–83.
  22. See Cogliati-Bantz, supra note 14, at 98–99.
  23. Victor Mosoti & Valerie Hickey, On the frontline of the climate crisis: Atoll nations and coastal communities with catastrophic threats to their homes and livelihoods also face serious legal implications, World Bank Blogs (Feb. 1, 2024),
  24. Louis Bélanger & Jean-Frédéric Morin, Treaty amendment procedures: A typology from a survey of multilateral environmental agreements, 37 LJIL 62 (2024) (“[f]or every two new treaties entering into force, an existing one is modified”).