Sea level rise
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This article is about the recent and projected rise in the world's average sea level associated with global warming. For sea level in general, see Sea level.
Sea level observations between 1993 and November 2018.
Historical sea level reconstruction and projections up to 2100 published in January 2017 by the U.S. Global Change Research Program for the Fourth National Climate Assessment.[1]
Since at least the start of the 20th century, the average global sea level has been rising. Between 1900 and 2016, the sea level rose by 16–21 cm (6.3–8.3 in).[2] More precise data gathered from satellite radar measurements reveal an accelerating rise of 7.5 cm (3.0 in) from 1993 to 2017,[3]:1554
which is a trend of roughly 30 cm (12 in) per century. This acceleration is due mostly to human-caused global warming, which is driving thermal expansion of seawater and the melting of land-based ice sheets and glaciers.[4] Between 1993 and 2018, thermal expansion of the oceans contributed 42% to sea level rise; the melting of temperate glaciers, 21%; Greenland, 15%; and Antarctica, 8%. Climate scientists expect the rate to further accelerate during the 21st century.[5]:62
Projecting future sea level is challenging, due to the complexity of many aspects of the climate system. As climate research into past and present sea levels leads to improved computer models, projections have consistently increased. For example, in 2007 the Intergovernmental Panel on Climate Change (IPCC) projected a high end estimate of 60 cm (2 ft) through 2099,[6] but their 2014 report raised the high-end estimate to about 90 cm (3 ft).[7] A number of later studies have concluded that a global sea level rise of 200 to 270 cm (6.6 to 8.9 ft) this century is "physically plausible".[8][3][9] A conservative estimate of the long-term projections is that each Celsius degree of temperature rise triggers a sea level rise of approximately 2.3 meters (4.2 ft/degree Fahrenheit) over a period of two millennia: an example of climate inertia.[2]
The sea level will not rise uniformly everywhere on Earth, and it will even drop in some locations.[10] Local factors include tectonic effects and subsidence of the land, tides, currents and storms. Sea level rises can influence human populations considerably in coastal and island regions.[11] Widespread coastal flooding is expected with several degrees of warming sustained for millennia.[12] Further effects are higher storm-surges and more dangerous tsunamis, displacement of populations, loss and degradation of agricultural land and damage in cities.[13][14][15] Natural environments like marine ecosystems are also affected, with fish, birds and plants losing parts of their habitat.[16]
Societies can respond to sea level rise in three different ways: to retreat, to accommodate and to protect. Sometimes these adaptation strategies go hand in hand, but at other times choices have to be made among different strategies.[17] Ecosystems that adapt to rising sea levels by moving inland might not always be able to do so, due to natural or artificial barriers.[18]
https://en.wikipedia.org/wiki/Sea_level_rise
