Why is there so much uncertainty in determining how fast sea level will rise in the future?
There are three reasons for the uncertainty in accurately projecting future sea level rise. (1) Sea level fluctuates annually as the oceans cool down and heat up, and therefore estimates of long term trends in sea level rise require data from many years. (2) Scientists are still discovering new information about how fast the ocean will warm or glacial ice will melt—and both of these factors cause global sea levels to rise. As a result, scientists use different global sea level rise scenarios to estimate how fast and how much sea level will rise (see Figure 2)1. (3) While all scientific models predict that the rate of sea level rise will increase in the future, these models differ because they attempt to predict future global changes that involve complicated environmental interactions, such as an ice-free Arctic Ocean accelerating the rate of Greenland’s glaciers melting, As shown in Figure 2, slight differences in the estimated rate of sea level rise results in large differences when projected a century into the future.
1 Parris, A., et al. 2012. Global Sea Level Rise Scenarios for the United States National Climate Assessment. National Oceanic and Atmospheric Administration. cpo.noaa.gov/sites/cpo/Reports/2012/NOAA_SLR_r3.pdf