Long-Term Sea Level Rise Scenarios

A recent study in the journal Nature Climate Change could be an excellent reading for a climate change course’s science modules, as well as discussion of the development of adaptation scenarios and responses. The study, which focuses on long-term (2300) projections of sea level rise under 1.5C and 2.0C temperate rise scenarios employed a semi-empirical model calibrated with sea-level data from the past millennium to make these projections. The study also has implications for the timing of emissions reductions over the course of this century.

Among the take-aways of the study:

  1. Reducing temperature increases to 1.5-2C from the reference case halves projected sea level rise rates by 2100, but the rise is still three times the present rate at that point
    1. Even under the impossible scenario of zero greenhouse gas emissions by 2016, sea level rise rates are still double present day values by the 2050s, thought the rate slowly declines thereafter
  2. While the reference scenario leads to sea level rise of 102 (72-139) centimeters over the course of the 21st Century, the 1.5 and 2C scenarios limits sea level rise to about 7 centimeters by 2100. However, this would require negative emissions mechanisms, e.g. biomass or carbon capture and sequestration;
  3. By 2300, sea levels are projected to increase by 2.7 (1.6-4.0) meters in a scenario in which there is a 50% possibility of limiting warming to 2C, twice the present-day rates;
    1. Under a higher probability 2C sea level rise is limited by 2.0 meters (1.2-3.1)
    2. The 1.5C scenario limits sea level rise to 1.5 meters (0.9-2.4)
  4. If mitigation is delayed for many decades, the large inertia in the system will preclude preventing sea level rise of less than 1.6 meters, perhaps as high as 4.2 meters by 2300, even with extremely aggressive mitigation policies;
  5. Ocean inertia ensures that about half of twenty-first century sea level rise is already baked into the system at this point as a consequence of past emissions

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