US scientists raise bar for sea level by 2100

This handout photo taken on March 26, 2016 and released by NASA shows a perspective of the northeast coastline of Greenland, one
This handout photo taken on March 26, 2016 and released by NASA shows a perspective of the northeast coastline of Greenland, one of the world's two great ice sheets, whose melting could contribute to rising sea levels

In the last days of Barack Obama's administration, US government scientists warned even more sea level rise is expected by century's end than previously estimated, due to rapid ice sheet melting at the poles.

The report by the National Oceanic and Atmospheric Administration (NOAA) set the "extreme" scenario of global average sea level rise by 2100 to 8.2 feet (2.5 meters), up half a meter from the last estimate issued in 2012.

"We raised the upper limit of our scenarios," lead author William Sweet told AFP.

"It is possible. It has a very low probability. But we can't discount it entirely."

The figures are among the highest ever issued by the US government, and take into account new scientific studies on the disappearing ice cover in Greenland and Antarctica.

"Recent (scientific) results regarding Antarctic instability indicate that such outcomes may be more likely than previously thought," said the report, released on January 19.

It also revised the lower end of the anticipated range, saying nearly one foot (0.3 meters) is expected by 2100, up from four inches (0.1 meters) previously.

This put the NOAA report closer in line with the 2013 United Nations Intergovernmental Panel on Climate Change, which said would likely rise from one to three feet by the end of the century.

The US space agency NASA has also warned that significant sea level rise is "unavoidable," given mankind's continued burning of fossil fuels like oil and gas that contribute to warming the planet.

In 2015, NASA said the Earth is likely locked in to at least three feet of sea level rise, and probably more.

But the big question remains: how soon? Researchers do not know how soon the seas will rise, and whether they will hit these levels in this century or beyond.

"We are not projecting anything. Everything is dependent on the amount of future heating, ocean and atmospheric heating," explained Sweet.

Localized results

Though experts warn that the past is not an accurate predictor of future sea level rise, global average sea level has climbed eight to nine inches since 1880, when modern record-keeping began.

Much of that has taken place in recent years, as global warming has accelerated. Seas around the world have risen an average of nearly three inches since 1992.

The NOAA report also pointed to regional dangers of sea level rise, with some portions of the US coast more likely to see above-average rise and increased flooding than other parts of the world.

"The world's ocean is not going to rise like water in a bathtub," said Sweet.

With the exception of Alaska and the Pacific Northwest, almost all US coasts are expected to see greater than global average sea level rise in the next eight decades.

Land in Alaska is rising, but in Louisiana and along the Gulf Coast and the mid-Atlantic, it is sinking.

Other factors, like changing ocean circulation in some parts of the planet, affect how much oceans mount in various places.

As ice sheets melts, the gravity around Earth will change as the planet loses mass, causing some areas to see higher or lower rise than the global average.

Recent research has shown that about three feet of "would permanently inundate areas currently home to two million Americans," said the report.

Six feet would flood the homes of six million people in the United States.

Sweet said the report's release was not planned to coincide with the end of the Obama presidency, or to precede the inauguration of Donald Trump, who has expressed doubts about climate change and pledged to increase fossil fuel extraction in the United States.

"The timing might look suspect," Sweet said.

"But no, this has actually been in the works for over a year."

Explore further

Regional sea-level scenarios will help Northeast plan for faster-than-global rise

© 2017 AFP

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Jan 24, 2017
Data from NOAA's own website contradicts their alarming predictions. Global sea level rise still averages 1.5 mm per year as measured by tide gauges or 3.4 mm per year measured by satellites. That's 6 or 13 inches per 100 years or another 5 or 11 inches by 2100. There has been no significant acceleration in sea level rise over the entire record.

Why tide gauges show 1.5 mm/yr and satellites show 3.4 mm/yr is a subject for debate about the accuracy of the measuring devices and the methods to determine a global average, but in neither record is there any significant acceleration of sea level rise that would support a prediction of 1 to 2.5 meters (3 to 8 feet).

Current sea level trends from satellite measurements:

Current sea level trends from tide gauges (NOAA):

Jan 24, 2017
Why highlight the alarmist figure of 2.5m if, as stated, it has a "very low probability". Good grief.

Jan 24, 2017
More FAKE "science" from the AGW Cult and their alternate reality built on alternate facts.

Jan 24, 2017
'Dream' winter conditions, except it's summer.

Whatever happened to summer? Cardrona Alpine Resort woke up to its heaviest summer snowfall in living memory yesterday, 30cm covering the base.
All over the world this is happening.

Jan 24, 2017
US scientists lowers bar for science.

There fixed that headline.

Jan 25, 2017
What AKSDAD said.

Yes, 8.2 feet by 2100 comes to 29 mm/yr, or ten times the current rate. When is this dramatic speed up going to begin to happen? Does anyone ever do the arithmetic?

Jan 25, 2017
More FAKE "science" from the AGW Cult and their alternate reality built on alternate facts.

More monkey chatter from antisciencgorilla and all his dumb socks above with with thumb sucked opinions, feel that hot warm fuzzy feeling inside your head, thats hot air ;)

Jan 25, 2017
Focusing on the estimated upper bound shows how narrow minded some people are, or just points to their lack of reading and comprehension abilities. None of the deniers are commenting on the fact that the lower bound has been increased to be about a foot rise by end of century? Uh-oh. this matches current trends, not accounting for a possible melt acceleration. Some Manhattan Project members thought a nuclear device might ignite the Earth's atmosphere, even though it was very unlikely, but still reported their concerns. If deniers would stop focusing on the worst case scenario, you would see that the projections/estimations/possibilities are not always alarming, but do point to concern.

Jan 25, 2017
You know, @askdad has some good links. The link to shows average sealevel rise since has been a linear increase of 3.4mm/yr. Please DO visit that link. While you are there scroll down and follow the link, "10 things you should know about sea level rise and how bad it could be". It blows away all of the Denier Goon Squad math and explains exactly why sealevels could rise quickly (non-linearly) to levels of 8+ feet by 2100.

If the denier goons would only be realistic and look at Miami street flooding from sea-level rise and compare with it the recent past (say 20 years back), it should be a no-brainer how quickly AGW pollutants have impacted ocean levels.


Feb 13, 2017
The focus should be on the likely outcome.
Niether the lowest (1 foot) or the highest (9ft) are likely. They are possible, but unlikely.
The most likely scenario is somewhere in the middle - 4 feet to 6 feet.
A 4 foot rise would still be catastrophic, especially for Miami, New Orleans, and other coastal cities.
Don't forget, the sea level rise keeps going, and rises faster in the next century.

Miami and New Orleans may have to be abandoned. Billions will need to be spent modifying and protecting other ports and cities.

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