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Sea Level Rise

New York Projections and Impacts

aerial view of Long Island
Rising seas and increased storm surges will
put New York's coastlines at risk.

Global mean sea level has been generally rising since the end of the last ice age. In the 18th and 19th centuries the rise was small, but during the 20th century the seas rose faster, primarily because ocean waters have warmed and expanded, and larger volumes of meltwater from mountain glaciers are now reaching the sea.
Conservative projections expect the seas will rise by 7 to 23 inches by 2100, but do not account for rapid melt of land-based ice. The latest studies take into account rapid ice melt, which we are already observing, to project a rise in global mean sea level of three feet or more.
Rising sea levels pose serious threats to coastal communities and natural resources, both worldwide and in New York. To ensure the future usability and security of facilities, transportation and critical resources (such as drinking water), government officials and private sector planners need the best available sea level rise projections.

How Sea Level Rise Will Impact New York

Well over half of New Yorkers live in marine coastal counties. Already, many communities and natural resources along the ocean coast and tidal portions of the Hudson River are at risk to damaging storms. This risk affects not only built resources, but also critical ecosystem services such as flood buffers, drinking water protection and species habitat.

According to the 2007 Northeast Climate Impacts Assessment by the Union of Concerned Scientists, as seas rise

  • The risk of severe flooding and storm damage will increase;
  • Beaches and bluffs will suffer increased erosion;
  • Low-lying areas will be inundated, with potential for saltwater to infiltrate into surface waters and aquifers;
  • Sewage and septic systems, transportation and water treatment infrastructure will be at risk from flooding and erosion.

Sea Level Rise Projections

Global Mean Sea Level Rise

During the past century the rate of global mean sea level rise was about 1.7 millimeters per year (0.7 inches per decade), and observations indicate that the rate of global sea level rise is accelerating.

The Intergovernmental Panel on Climate Change (IPCC), an ongoing international scientific study sponsored by the United Nations, projects a rate of sea level rise during the 21st century faster than the rate observed since 1970. The panel's 2007 projection assumed gradual melting of land ice, leading to a likely rise in global sea levels of 7 to 23 inches by 2100. More recent analysis, which takes into account rapid melting of land-based ice sheets (particularly in Greenland and west Antarctica) and probable future warming scenarios, projects a global mean sea level rise of 20 to 55 inches above the 1990 level by 2100.

Relative Sea Level

The term relative (or local) sea level refers to the height of the sea relative to some land benchmark. Relative sea level takes into account both global sea level and certain local factors, including subsidence or uplift of the earth's crust in response to changes in glaciation or extraction of groundwater, oil or gas; tectonic activity; sediment consolidation; and short-term climatic fluctuations (e.g., El Nino Southern Oscillation).

New York State Sea Level Rise Projections

Tide-gauge observations indicate that rates of relative sea level rise in New York State were greater than the global mean, ranging from 2.41 to 2.77 millimeters per year (0.9 to 1.1 inches per decade) over the last century.

The State Sea Level Rise Task Force, charged by the Legislature with developing recommendations for adapting to sea level rise, adopted the sea level rise projections in the table below for two regions of New York State. Although these projections have not been officially adopted by the Legislature or any New York State agency for regulatory purposes, DEC considers them the best available projections for planning purposes.

Projected Sea Level Rise in Two Regions of New York (ClimAID Integrated Assessment, 2010)
Lower Hudson Valley & Long Island 2020s 2050s 2080s
Sea level rise 2 to 5 in 7 to 12 in 12 to 23 in
Sea level rise with rapid ice-melt scenario 5 to 10 in 19 - 29 in 41 to 55 in
Mid-Hudson Valley & Capital Region 2020s 2050s 2080s
Sea level rise 1 to 4 in 5 to 9 in 8 to 18 in
Sea level rise with rapid ice-melt scenario 4 to 9 in 17 to 26 in 37 to 50 in

The figures for sea level rise represent the central range (middle 67%) of values from model-based probabilities (16 global climate models by 3 greenhouse gas emissions scenarios) rounded to the nearest inch.

The figures for sea level rise with rapid ice-melt scenario are based on acceleration of recent rates of ice melt in the Greenland and west Antarctic ice sheets and paleoclimate studies.

How Sea Level Rise Projections are Made

The technical basis for sea level rise projections is found in the following peer-reviewed publications, as well as in the report of the Sea Level Rise Task Force and the ClimAid Integrated Assessment for Effective Climate-change Adaptation Strategies in New York State (available from New York State Energy Research and Development Authority, 17 Columbia Circle, Albany, NY 12203).

  • Rahmstorf, S. 2007. A semi-empirical approach to projecting future sea-level rise. Science, 315(58):368-370.
  • Titus, J.G. 2009. Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region. Synthesis and Assessment Product 4.1. U.S. Climate Change Science Program. 298pp. This work can be found at http://www.epa.gov/climatechange/effects/coastal/sap4-1.html (see Mid-Atlantic Coastal Sensitivity link on right).

More about Sea Level Rise:

  • Sea Level Rise Task Force - Learn about the work of the Sea Level Rise Task Force that was created in 2007 by the New York State Legislature.