Research: Sea-levels rising faster than IPCC projections

Nov 28, 2012

Sea-levels are rising 60 per cent faster than the Intergovernmental Panel on Climate Change's (IPCC) central projections, new research suggests.

While temperature rises appear to be consistent with the projections made in the IPCC's fourth assessment report (AR4), show that sea-levels are actually rising at a rate of 3.2 mm a year compared to the best estimate of 2 mm a year in the report.

The researchers, from the Potsdam Institute for Climate Impact Research, Tempo Analytics and Laboratoire d'Etudes en Géophysique et Océanographie Spatiales, believe that findings such as these are important for keeping track of how well past projections match the accumulating observational data, especially as projections made by the IPCC are increasingly being used in decision making.

The study, which has been published today, 28 November, in IOP Publishing's journal Environmental Research Letters, involved an analysis of and sea-level data over the past two decades, comparing them both to projections made in the IPCC's third and fourth assessment reports.

Results were obtained by taking averages from the five available global land and series.

Graphic showing the largest cities vulnerable to rising sea waters by the year 2070. Sea levels are rising 60 percent faster than a previous UN climate panel forecast, scientists reported on Wednesday.

After removing the three known phenomena that cause short-term variability in global temperatures – solar variations, volcanic aerosols and El Nino/Southern Oscillation – the researchers found that the overall warming trend at the moment is 0.16°C per decade, which closely follows the IPCC's projections.

Satellite measurements of sea-levels showed a different picture, however, with current rates of increase being 60 per cent faster than the IPCC's AR4 projections.

Satellites measure sea-level rise by bouncing radar waves back off the sea surface and are much more accurate than tide gauges as they have near-global coverage; tide gauges only sample along the coast. Tide gauges also include variability that has nothing to do with changes in , but rather with how the water moves around in the oceans, such as under the influence of wind.

The study also shows that it is very unlikely that the increased rate is down to internal variability in our climate system and also shows that non-climatic components of sea-level rise, such as water storage in reservoirs and groundwater extraction, do not have an effect on the comparisons made.

Lead author of the study, Stefan Rahmstorf, said: "This study shows once again that the is far from alarmist, but in fact has under-estimated the problem of climate change. That applies not just for sea-level rise, but also to extreme events and the Arctic sea-ice loss."

Explore further: Average temperature in Finland has risen by more than two degrees

More information: Comparing climate projections to observations up to 2011, Stefan Rahmstorf et al 2012 Environ. Res. Lett. 7 044035. iopscience.iop.org/1748-9326/7/4/044035/article

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User comments : 10

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Wolf358
1.6 / 5 (7) Nov 28, 2012
Ummm... Could the actual volume of the ocean be increasing because of the additional CO2 it's absorbing?
Mayday
2.3 / 5 (6) Nov 28, 2012
Curious map. Many of the values seem well on the low side. And whole continents are ignored. A more complete and accurate rendition would certainly be eye-opening. I almost said it would be "alarming," but I think that's a no-no.
Anonym
1.6 / 5 (13) Nov 28, 2012
Ah, the Mighty Wurlitzer of global warming grinds on. There needs to be a study of the various studies, their provenance and sources of funding, in order to analyze the likelihood that the study in question is in fact not pure propaganda, a la Michael Mann. ... Establishing global sea level is a notoriously difficult problem. For example, it's been rising quite rapidly on the middle Texas coast for decades -- not due to higher water but due to lower land (subsidence); it's now probably a foot higher than 50 years ago, far outstripping the puny rate of rise predicted by this study. (No sign anyone on the Texas coast is panicking yet, though. Ignorant Texans, get with the program!)

Is it merely coincidental that this study closely follows "superstorm" Sandy (a below-average storm with an above-average surge due to the state of the tide and the negligence of NYC to protect its infrastructure from a predictable flood --- kinda reminiscent of superstorm Katrina, huh?).
VendicarD
4.1 / 5 (9) Nov 28, 2012
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...
It isn't happening... It isn't happening...

And if it is happening, then it still isn't happening.
Mayday
1.9 / 5 (9) Nov 28, 2012
Across the entire span of recorded human history mankind has been dealing with a rather continuously rising sea level. I'd bet that somewhere under the sands of Iraq there sits a cracked cuniform tablet decrying the same hopeless fate. But then again, wasn't it climate change that cleaned the Babylonians' clock as well? Never mind.
nuge
5 / 5 (3) Nov 28, 2012
Ummm... Could the actual volume of the ocean be increasing because of the additional CO2 it's absorbing?


No, it is because the global average temperature is increasing. This actually causes thermal expanison of the water in the same way that metals expand when left out in the sun.
Caliban
5 / 5 (2) Nov 29, 2012
Ah, the Mighty Wurlitzer of global warming grinds on. There needs to be a study of the various studies, their provenance and sources of funding, [...]


Why? Far less expensive for you to check the article itself, wherein that info will be detailed. Prolly funded by NAS, NSF...prolly NOT by Heritage, Cato...

Establishing global sea level is a notoriously difficult problem.[...] No sign anyone on the Texas coast is panicking yet, though. Ignorant Texans, get with the program!)


Not so difficult anymore, with the GRACE satellite program data now available. You should read up on it!

Is it merely coincidental that this study closely follows
"superstorm" Sandy


Yes, Yes it is, Uncle Anonym. Notoriously difficult to pre-schedule publication of a peer-reviewed journal article months ahead, while accurately predicting the future coincidental landfall of a tropical atlantic superstorm that was itself diverted to its "target" by an anomalous high pressure ridge.
Caliban
5 / 5 (2) Nov 29, 2012
Curious map. Many of the values seem well on the low side. And whole continents are ignored. A more complete and accurate rendition would certainly be eye-opening. I almost said it would be "alarming," but I think that's a no-no.


I could be wrong, but from my reading, the numbers on the map were intended to represent the (projected) number of the vulnerable people in each city, as opposed to the total population of each of the cities.

gregor1
1 / 5 (4) Nov 30, 2012
This seems to be contradicted by this
http://www.bbc.co...20543483
ubavontuba
1 / 5 (5) Dec 01, 2012
Research: Sea-levels rising faster than IPCC projections
Well then, they must be idiots, as the sea level has been rising at a steady rate for quite some time now.

http://sealevel.colorado.edu/

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