Title: Sea Level Rise | National Climate Assessment
Headings: Sea Level Rise
Sea Level Rise
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Sea Level Rise
Convening Lead Authors
Lead Authors
Contributing Authors
Introduction
Key Message 10: Sea Level Rise
Sea Level Rise
Figure 2.26: Past and Projected Changes in Global Sea Level Rise

Content: 18
Like mercury in a thermometer, water expands as it warms up (this is referred to as “thermal expansion”) causing sea levels to rise. Melting of glaciers and ice sheets is also contributing to sea level rise at increasing rates. 19
Since the late 1800s, tide gauges throughout the world have shown that global sea level has risen by about 8 inches. A new data set (Figure 2.25) shows that this recent rise is much greater than at any time in at least the past 2000 years. 1
Since 1992, the rate of global sea level rise measured by satellites has been roughly twice the rate observed over the last century, providing evidence of additional acceleration. 16
Projecting future rates of sea level rise is challenging. Even the most sophisticated climate models, which explicitly represent Earth’s physical processes, cannot simulate rapid changes in ice sheet dynamics, and thus are likely to underestimate future sea level rise. In recent years, “semi-empirical” methods have been developed to project future rates of sea level rise based on a simple statistical relationship between past rates of globally averaged temperature change and sea level rise. These models suggest a range of additional sea level rise from about 2 feet to as much as 6 feet by 2100, depending on emissions scenario. 20
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It is not clear, however, whether these statistical relationships will hold in the future, or that they fully explain historical behavior.