FIGURE 7.1 Illustration of relative sea level rise since the last ice age: 26,000 years ago, sea level is estimated to have been about 400 feet (120 meters) lower than it is today. This curve was assembled using analyses of coral reefs all over the world. The abbreviation MWP refers to various meltwater pulses, which caused sea level to rise relatively rapidly. MWP-1AO, ~19,000 years ago; MWP-1A, ~14,600 to 13,500 years ago; MWP-1B, ~11,500 to 11,000 years ago; MWP-1C, ~8,200 to 7,600 years ago. SOURCE: Gornitz (2009).

(Church and White, 2006); in the last half of the 20th century, this increased to approximately 0.07 inches (1.8 millimeters) per year (Miller and Douglas, 2004); and over the past 15 years, the rate of sea level rise has been in excess of 0.12 inches (3 millimeters) per year (Katsman et al., 2008; Vermeer and Rahmstorf, 2009). Ice core records show that atmospheric CO₂ concentrations have been rising since about 1830 (see Chapater 6), so sea level and CO₂ increases are generally coincident. Clear indications of interannual and decadal variability can also be seen in Figure 7.2. Distinguishing the effects of natural climate variability from human-caused warming is one of the challenges of understanding the details of past sea level rise and anticipating its future course.