Frequently Asked Questions
General questions
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Is sea level rise happening now?
Satellite altimeters are currently (1993-present) measuring a rate of 3.3 mm per year of global mean sea level rise.
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Are sea levels rising the same all over the world, as if we're filling a giant bathtub?
No. Sea level rise is uneven, the two main reasons being ocean dynamics and Earth’s uneven gravity field.
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How does El Niño fit into the sea-level rise picture?
Over periods of 2-8 years, after removing the overall trend of about 3 millimeters per year, the globally averaged sea-level rise closely follows the waxing and waning of El Niño.
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How much rise should we expect from Greenland and Antarctica?
Currently the total sea level rise is about 3 millimeters per year (about 1/8 of an inch per year). Of that amount, about one-third comes from Greenland and Antarctica, one-third from glaciers like those in Alaska or the Himalayas, and one-third from the expansion of seawater as it warms.
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What causes sea level rise?
Most of the observed sea level rise (about 3 mm per year) is coming from the meltwater of land-based ice sheets and mountain glaciers, which adds to the ocean’s volume (about 2 mm per year combined), and from thermal expansion, or the ocean water’s expansion as it warms (roughly 1 mm per year).
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How long have sea levels been rising? How does recent sea level rise compare to that over the previous centuries?
Between about 21,000 years and about 11,700 years ago, Earth warmed about 4 degrees C (7.2 degrees F), and the oceans rose (with a slight lag after the onset of warming) about 85 meters, or about 280 feet. However, sea levels continued to rise another 45 meters (about 150 feet) after the warming ended, to a total of 130 meters (from its initial level, before warming began), or about 430 feet, reaching its modern level about 3,000 years ago.
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How much do human activities contribute to sea level rise?
Many lines of evidence demonstrate that human activities, especially greenhouse gas emissions from fossil fuel combustion, are primarily responsible for the climate changes observed in the industrial era, especially over the last six decades. Human-induced greenhouse gas emissions are the only factors that can account for the observed warming over the last century that is driving the observed sea level rise; there are no credible alternative human or natural explanations supported by the observational evidence.
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I've heard I won't be able to access data that I used to download through FTP. What happened?
NASA will soon be changing the file transfer protocol, a system for browsing and retrieving data, now in use on the NASA Sea Level Portal.
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