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Indicator : indicator-sea-level-rise-2018
Indicator: Global Sea Level Rise
Key Messages: 1. Global sea level has risen by about 8 inches since scientific record keeping began in the 1880s. The rate of global sea level rise has increased in recent decades. The current rate is a little more than an inch per decade. 2. Sea level rise is primarily driven by two factors related to climate change. The first factor is “thermal expansion” – as ocean temperatures rise, the water expands. The second factor is melting of land ice (ice sheets and glaciers), which adds water to the world’s oceans. 3. Sea level rise is not uniform across the globe. Coastal communities are affected by their local sea level rise, which combines global sea level rise, changes in local land elevation, tides and winds. In Louisiana, for example, local sea level is rising about 4 inches per decade because the land is sinking and sea level is rising. 4. Sea level rise and climate change-related threats like high tide and storm-surge flooding are affecting social, economic, and ecological systems along the U.S. coasts. Full Summary: Rising global sea level is a critical consequence of climate change. As the ocean waters warm, they expand. Also, as air temperatures warm, water from melting ice sheets, polar ice caps, and glaciers, enter into our ocean basins. Global sea level rise is measured by tide gauges, which provide global estimates since the 1880s, and by satellites, which do so since 1993. Global mean sea level (GMSL) has risen by about 7–8 inches (about 16–21 cm) since 1900, with about 3 of those inches (about 7 cm) occurring since 1993. Human-caused climate change has made a substantial contribution to GMSL rise since 1900, contributing to a rate of rise greater than during any preceding century in at least 2,800 years. In addition to the global average sea level rise, local sea level rise – sometimes called “relative sea level rise” – happens at different rates in different places. Local sea level rise is affected by the global sea level rise, but also by local land motions, and the effects of tides, currents, and winds. Many places along the United States coast have seen their local sea levels rise faster than the GMSL. As sea levels have risen, the number of tidal floods each year that cause minor impacts, often called “nuisance floods,” have increased 5- to 10-fold since the 1960s in several U.S. coastal cities (very high confidence). Rates of increase are accelerating in over 25 Atlantic and Gulf Coast cities (very high confidence).
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