Sea level rise has slowed… temporarily

By Phil Plait | August 26, 2011 9:14 am

Over the past 10 years at least, sea levels have been rising relatively steadily. This is mostly due to melting glaciers and ice sheets, and is a natural — if detrimental — consequence of global warming. The rate of ocean level rise has been a little over 3 millimeters per year (about 1/8th of an inch per year)… until last year. The rate of increase suddenly reversed itself in 2010, and the sea levels actually dropped a bit, by about 6 mm. What happened?

La Niña happened. Equatorial ocean temperatures fluctuate on a cycle; when they are warmer it’s called an El Niño, and when they’re cooler it’s La Niña. As you might expect, this affects how water evaporates off the ocean surface, and therefore rainfall across the world as well. Right now we’re in a La Niña, characterized by drought conditions in the southern US (like in Texas), and heavier than usual rainfall in Australia, northern South America, and other locations:

That map is from the NASA/German Aerospace Center’s Gravity Recovery and Climate Experiment (GRACE) satellites, which map where water is on the Earth and how it moves around. This change in rainfall is the culprit for the lowering sea level:

So where does all that extra water in Brazil and Australia come from? You guessed it–the ocean. Each year, huge amounts of water are evaporated from the ocean. While most of it falls right back into the ocean as rain, some of it falls over land. "This year, the continents got an extra dose of rain, so much so that global sea levels actually fell over most of the last year," says Carmen Boening, a JPL oceanographer and climate scientist. Boening and colleagues presented these results recently at the annual Grace Science Team Meeting in Austin, Texas.

That’s pretty interesting! I didn’t realize it could rain so much that sea levels could be affected, but there you go. Doing the math, I find that a 6 mm drop is equivalent to a volume of very roughly 700 billion cubic meters of water, or 700 cubic kilometers (about 180 cubic miles). That is a lot of water! Spread out over so much area though — Australia alone is 3 million square km — it gets thinned out considerably. Still, all that extra rain is no picnic; floods in Australia killed several dozen people over the past year and destroyed a vast amount of industry and infrastructure there.

Mind you, as I said increasing sea levels are an indicator of global warming, since ice melting in Greenland, for example, flows into the ocean. Does this mean the drop in sea level indicates global warming has reversed?

Nope. El Niño and La Niña conditions are cyclical, swapping every few years. As global warming continues, the sea levels will rise steadily, but superposed on top of that are the effects of short-period oscillations like El Niño and La Niña. It’s very common in science to see a linear trend with a cycle on top of it; you have to be careful when interpreting such a plot to know if what you’re seeing is long-term change or short-term.

This decrease in sea level is short-term, and when we switch back to El Niño conditions — warmer equatorial ocean temperatures — the trend will reverse once again, and sea levels will start to rise steadily.

I’m writing about this for two reasons. One is that I think it’s interesting science, and shows how important it is to understand trends that can add or subtract from each other, and how satellite data are critical to understanding our environment.

The other reason is, of course, that I expect we’ll be hearing from global warming deniers who will tout this finding as more proof that climate change isn’t happening. I want to head that off at the pass. These data show that the world’s weather does change on a short time scale, but once you account for that, the imprint of global warming is still there, still real, and still affecting us all.

Image credits: Sea level measurements: S. Nerem, University of Colorado; GRACE water map: NASA/JPL-Caltech.

Related posts:

Dramatic glacial retreat caught by NASA satellite
As arctic ice shrinks, so does a denier claim
NASA talks global warming
Our ice is disappearing

CATEGORIZED UNDER: Antiscience, Science

Comments (57)

  1. Mac

    “This decrease in seal level is short-term…”

    what is seal level? 😀

  2. Thanks phil. are you able to detail the science behind how the measurements are taken? I’ve always been curious how you factor in the tides, climate etc

    Cheers from australia, scott

  3. Sir Eccles

    Bah, I was expecting some sort of “your mamma so fat…” joke. Very disappointed.

  4. Mike

    This will appear as “sea level rise stopped” on the Drudge Report and ever RW blog in 3 … 2 … 1 …

  5. Pepijn

    @Sir Eccles: you mean: “Yo mama so fat, when she gets out of the water global sea levels drop by 6 mm”?

  6. Gabriel

    Wish we were getting some of that rain this year. Trees are dying and ground is bone dry to three feet deep. I’m willing to bet that we will have over 100 day at 100f or more.

  7. Chris

    Phil are you going to fix your black hole size calculation? It’s really bugging me :-)

  8. Michael Ralston

    Actually, I’m curious – should we expect that in a few years sea level will spike up to return to the trend, or should we expect some period of ‘stall’ in the rise, after which it will resume at the previous rate but won’t actually return to the same long-run trend?

    Sitting here just thinking about the matter, I can see arguments for either way.

  9. Tony

    Actually, Michael, what we will probably see is the trend continuing but with a period of ‘overshoot’ where it is temporarily ABOVE the trendline, before returning to the average…

  10. QuietDesperation

    Wish we were getting some of that rain this year.

    We had wonderful rain in So Cal this last winter. We’re nicely stocked for the first time in a while. (^▼^) Anyone says the word drought gets picked on and we put dirt in their hair. We are also having yet another mild, spring-like summer going on as well. If this is Climate Change, I say pump more CO2 stat! C’mon, Chinese people, buy more cars! Buy ALL the things!

    Phil are you going to fix your black hole size calculation?

    Holy crap! That’s the solution to rising sea levels! A black hole! Quick! Call CERN!!1!!!2! Just, like, fire the LHC into the sea!

  11. Beau

    It COULD be La Nina, but I think it’s way more likely that this definitively proves global warming is a hoax perpetrated by scientists attempting to falsify data for their own evil agenda!


  12. Theron

    It’s all about Al Gore being fat and his varying rate of water retention I’m sure.

    That map of extra water/drought I’m sure is accurate — that said, it shows Nashville in red, and we got enough rain in the period referenced to break a long semi-drought and refill the reservoirs.

  13. Phil Plait, world-famous scientist and global-warning alarmist says:

    … in 2010, … the sea levels actually dropped a bit, by about 6 mm.
    … the drop in sea level indicates global warming has reversed
    … I expect we’ll be … finding [this] as more proof that climate change isn’t happening.

    :-) :-) :-) :-)

    Isn’t “taken out of context” fun?

  14. MartinM

    The effect of the strong El Nino of 1998 is also clearly visible in the graph.

  15. itzac

    Yes, Beau. Clearly oil companies, who have no stake whatsoever in the outcome of this “debate”, are simply looking out for us so we don’t waste effort worrying about this. =P

  16. MHS

    Funny how the Mean Sea Level values in the top graph are pretty much at 1:1 scale (at least in my browser).

  17. Renee Jones

    The main GOP candidates are all anti-science nitwits. Obama the “cave” man caves into any GOP demands. Either way, its four more years of time wasted as the climate situation gets worse and worse.

    The real problem is ignorant, irrational GOP voters that blindly believe any lie their self-proclaimed leaders tell them. Unless the voters wake up, you better get out the mouse picture … we are doomed. Given the hatred of intelligence in this country, it’s hopeless.

  18. MikeG

    Hey Phil, how did you get the “700 billion cubic meters of water” figure?

    Isn’t a radius of about 6300 km with a surface area of about 5 x 10E14 square m and volume of about 2.1 x 10E12 cubic m?

    That sounds more like 2000 billion cubic meters.

  19. Tom Scharf

    Weird, I thought the predictions were for ACCELERATING sea level rise in response to business as usual CO2. Otherwise all those scary predictions about 3M to 5M rise by 2100 would be unjustified.

    Looks pretty linear, even possibly decelerating now.

    I guess nobody here thought about that. I guess the models count more than reality.

  20. MartinM

    Or possibly we understand the difference between noise and signal.

  21. andyd

    And for how long has the sea-level been rising like this?

  22. VinceRN

    This shows something else: We still don’t really know exactly what’s going on and how the system really works. Sure, we know there is a warming trend, and we know it partially, probably largely, due to our suddenly pumping carbon out of the earth and into the air. However, we really don’t know exactly what effect there will be, just hat there will be effects. Clearly any prediction that “sea level will rise by X over the next Y years” is inexact at the least. All we can really say is it will probably rise some overall.

    Two things about this I’m always curious about, and haven’t been able to find:

    First, how much does sea level vary normally – that is if we are not pumping CO2 into the atmosphere. Clearly it varies, over longer times it varies a lot, and there are other factors involved besides the El Nino/La Nina cycle. Unfortunately no exact measurements were taken until recently, so all we have is models and theories based on assumptions. Possibly good models and theories, but there short of a time machine we can;t get millimeter measurements yearly over the last thousand years or so.

    Second, if the predicted amount of ice melts what effect will it have on other factors besides sea level. what other effects would it have? The salinity of the oceans, since most of ice has little to no salt? What, if any, effects will this have? The albedo of the earth, as ice reflects more than what’s under it? A significant rise in sea level would also mean a significant increase in the surface area of the ocean, what effect would this have? Evaporation would certainly increase,a and therefore rain, but by how much and to what effect? This is a horribly complex system and almost everything we read deals with only a small part of it, as if that part existed in isolation.

    I’m sure research exist on these topics, but it’s not easily available to the general public like me.

    Again so people don;t jump on me as a denier, I deny nothing, clearly there is global warming, and clearly the changes humans are causing in the carbon cycle are involved. What I say is we don’t know enough, and we don’t know nearly as much as most of the people talking about this in the media claim we do scientists included.

  23. Interesting map and write up there BA. Thanks. :-)

    It has seemed like an awfully mild summer last year in Adelaide, South Oz and we’ve had a very wet start to August but the month has finished off with unusually dry conditions and above average temperatures too. That’s just one location on the planet and not necesarily typical natch.

    Wonder if 2011 like 2010 will be another record hot year?

    Are we shifting straight into an El Nino again now and will that make for a record peak in temps again? I suspect so.

    I gather there’s been a record heatwave in the US (click on my name for a good video on that & how it relates to the Anthropic Global Warming issue.) so that may be one indicator that’s likely. What happens in the Arctic – the region most dramatically affected by Human Caused Global Overheating is a key point of concern as well.

    Sadly, I’m sure this sea level phenomena will be used as a talking point to argue against the overwhelming evidence of the reality of the problem even as so much other powerful evidence against the climate contrarians case keeps building up. :-(

  24. Mekhong Kurt

    @Beau (#11), the presence of the smiley face at the bottom of your post suggests you’re joking. I surely do hope so!

    Phil, while I appreciate your efforts to head of the Tin Hat Brigade at the pass, if my own experience is any guide, they’ll at *best* simply ignore you, at at worst describe your biolgical connection to your Mother in unpleasant terms. AND ignore you afterwards. But keep it up. . . .

  25. QuietDesperation

    Unless the voters wake up,

    You really want that? If the voters truly began to see reality, both major Parties would quickly cease to exist.

  26. Pete Jackson

    It’s the BP oil blowout! All the water is going back down the hole they made. :-)

  27. Messier Tidy Upper

    @ 25. QuietDesperation : Which would be a bad thing why exactly?

    Incidentally, if folks here are after more info to read or watch when it comes to the sea level rise implications of Human Caused Global Overheating then I’d like to recommend :

    The relevant “Climate Crock” clip.


    Dr Jason Lowe from the Met Office Hadley Centre runs through the basics of the science in under 3 minutes.

    Plus :

    on the climate contrarian claim that sea level rises have been exaggerated. It hasn’t been and is :

    ” .. actually tracking at the upper range of the IPCC projections.”

    Of course, there’s plenty of other sites for information – and, regrettably, misinformation – online and in text and the media too.

  28. Spence_UK

    There is a bit more to this than some hand waving about el nino and la nina.

    The imprint from global warming, arguably most accurately measured from the ocean heat content, has flatlined for the last nine years or so. This is directly measured by NOAA using the ARGO floats (see below), and the value has been pretty much stalled for the last nine years.

    Since thermal expansion makes up around one-half of the sea level rise, we would expect the sea rise trend to have halved over the last nine years or so. Of course, this is difficult to measure because of the variability of ENSO superimposed on it.

    You can find the ocean heat content data here:

  29. don gisselbeck

    How much of that water went to replenishing aquafers? June in Western Montana

  30. don gisselbeck

    How much of that water went to replenishing aquafers? June in Western Montana probably had 10ish more cubic kilometers of snow water content than usual. (10,000 or so square kilometers above 2000 meters having at least a meter more than normal. Much of that ran off, but it has been rather dry for decades.

  31. Mike G

    @ Spence_UK
    In theory, oceanic heat content would be the most accurate way to measure global warming in the ocean. However, in practice measuring OHC is extremely problematic due to limited data coverage (most estimates are only for the upper 700-2000 meters- less than half of the average depth of the oceans) and data inhomogeneities (major issues comparing XBT, CTD, ARGO data). As a result, the NODC OHC estimate is only one of many, not all of which (e.g. Lyman et al, 2010) show the 9 year flatline you speak of. Indeed, given the energy imbalance seen in the satellite-derived TOA energy budgets, if OHC really has flatlined then it’s very hard to explain where all of that extra energy is going. The common assumption is that it’s simply accumulating in the deep ocean where we can’t measure it.

    Because of the “missing” heat, OHC estimates can provide a pretty good estimate of the lower bounds of thermal expansion, but the upper boundary is poorly constrained- i.e. we know that there is at least as much thermal expansion as accounted for by heat as we are able to measure, but we can’t say that there isn’t more thermal expansion due to the energy we can’t directly measure. Therefore we can attribute increases in MSL to thermal expansion, but we can’t attribute stagnation in SLR to stagnation in the OHC trend.

  32. Spence_UK


    Whilst what you say is plausible, it runs strongly against our current understanding and evidence, in a number of ways.

    Firstly, modelling suggests that approx. 80-90% of the heat transport in the oceans occur in the top 750 metres. For the deep oceans to suddenly dominate OHC trends would contradict our current understanding of the ocean. Now, models and our understanding can be wrong, I’m not disputing this. But to show an existing model wrong you really need supporting evidence, rather than assumptions.

    Secondly, although it is noisy, we do see initial evidence of a matching decline in the trend of the sea surface data. If the “missing heat” had moved to the deep ocean, we would not expect this decline in the trend. The decline in the trend above (measured by satellite altimetry) is also verified by the globally averaged GRACE measurements. And I’m not referring to the short term dip (2010-2011), but the longer term trend. Of course, these measurements remain noisy due to ENSO and probably require a few more years to be conclusive (and we don’t know if OHC is going to continue flatlining long enough to apply that test). A statistical estimate of sea level rise with the component of variance explained by ENSO removed might be informative here.

    So in summary – whilst your claim is not impossible, it is not strongly evidenced by the data to hand, and directly contradicts aspects of our current understanding of the science. This doesn’t go to say that you are wrong, but I would need some compelling supporting evidence to explain why you are right and our current understanding of the oceans is so wrong.

  33. Spence_UK


    To add some scientific detail to the my comment #33, I would take a look at the paper:

    “Sea level budget over 2003–2008: A reevaluation from GRACE space gravimetry, satellite altimetry and Argo” by Cazenave et al (easy to find on scholar google, freely available pdf on citeseer)

    This compares ARGO and GRACE measurements and verifies that the expansion rate from the Argos is quite consistent with the mass expansion of the oceans, but in turn not consistent with the idea that the heat has gone to the deeper ocean (which would necessarily include an unexplained component of the sea level rise).

  34. amphiox

    @ 25. QuietDesperation : Which would be a bad thing why exactly?

    It would be a bad thing if mass disillusionment leads to loss of faith in democracy itself, leaving the voters vulnerable to the blandishments of a charismatic third party demagogue with hidden authoritarian leanings.

    There is plenty of historical precedence for this.

  35. Messier Tidy Upper

    @ ^ amphiox : Maybe so. I must admit looking at the candidates, political carrying on and political system as it is – both in my country (Australia) and the United States – I kinda lose faith in democracy myself. :-(

    I think our political system (&, if I may be so bold, yours too) could do with a shake-up and some major reforms to improve it.

    Sometimes I think Isaac Asimov’s idea in his ‘Lucky Starr’ novels of a Council of Science running our planet may be the best way to go.

    Then again, they do say that : “Democracy is the worst of all possible systems of government – except for all its alternatives!” And there’s probably something to that as well.

  36. Gunnar

    @#36. MTU

    Perhaps the biggest problem with democracy is that it can only work well with a highly literate and well-informed public. If extreme idealogues of either the right or the left or both succeed in their aims of dumbing down the electorate they aspire to lead and rule, or if too few people commit themselves to becoming as well informed as they can, democracy will ultimately fail miserably.

  37. Gunnar

    Phil, I agree with MikeG @18. A drop of 6 mm (given that the oceans cover 70% of the earth’s surface) amounts to a volumetric decrease of closer to 2100 cubic kilometers than to 700 cubic kiometers. How did you come up with 700?

  38. Jack

    @Messier #36:

    We HAD a council of scientists called the Murray Darling Commission working out sustainable water allocations for SE Oz – but when the local farmers and small town residents heard the conclusions it all hit the fan big time!

    The Murdoch press, our uninformed AGW denier Opposition Leader, and local pressure groups win over science every time.

  39. Bob

    “Over the past 10 years at least, sea levels have been rising relatively steadily. This is mostly due to melting glaciers and ice sheets, and is a natural — if detrimental — consequence of global warming.”

    Phil – you forgot to mention the “Thermal Expansion” is one of the other reasons that sea levels are rising.

  40. adam

    “global warming is still there, still real, and still affecting us all.”

    Speak for yourself. I feel fine.

  41. Mike G

    Nothing about the assumption that the missing heat is going into the deep ocean is contrary to our modern understanding of heat transport in the oceans. We know for a fact that large amounts of heat are being transported to the deep ocean, even down to 6000m, because we’ve measured significant warming of bottom water (See von Schuckmann et al, 2009 and Johnson et al, 2007 ) . Even the Argo data show significant interannual variation down to 2000m, so we know that energy is being transported to depth more quickly than we used to think it was. What we don’t know is how much energy is getting down there. At least one model (Katsman and van Oldenborgh, 2011) suggests that the deep ocean sink could account for about 35% of the missing heat during the flatline period. That’s hardly an insignificant amount of energy.

    As for the deep ocean warming contradicting GRACE and Argo measurements, see Song and Colberg, 2011. They performed a similar exercise to Cazenave et al (and explain the relationship between their findings and Cazenave’s). They find thermal expansion of the deep oceans to be entirely consistent with observed changes in ocean mass and sea level.

  42. hhEb09'1

    Gunnar (#38), MikeG (#18), I’m getting Phil’s numbers. Are you squaring pi again? :)

  43. In the shameless self-promotion category, here’s my post on ocean heat content at SkS:

    Yes, the upper ocean is still warming, and the deep ocean too. On shorter timescales (up to a decade) some climate models (Palmer 2011) show upper ocean cooling is possible, but long-term the oceans will continue to warm for centuries because the increase in greenhouse gases has altered the thermal gradient in the ocean ‘cool-skin’ layer. Equilibrium won’t be reached for at least a 1000 years – based on modelling projections.

    Mike G – IIRC Katsman & Oldenburgh (2011) suggest most of the excess ocean heat is radiated back out to space.

  44. Spence_UK

    Thanks Mike G, I hadn’t read some of those papers.

    A couple of notes. Firstly, you note we have observed some warming of the deep oceans; but the measurements are temporally and spatially too sparse to draw any firm conclusions from this. That is even noted in the abstract of the last paper you cite (mixed messages?)

    The other papers you link are recent, unvalidated models – essentially hypotheses, and once again as an example this is made extremely clear both in the abstract and conclusions of the last paper. Also, that particular paper relies heavily on large uncertainties both in the deep ocean heat and highly inaccurate TOA radiation measurements. These wide errors allow you to fit pretty much any hypothesis you want in.

    All in all: I’m not terribly impressed. Perhaps these newly generated hypotheses based on unvalidated models will stand the test of time, but until some evidence supporting them appears I’ll remain sceptical, and stick with the hypotheses that have observational support.

    Also: it wouldn’t surprise me if the oceans exhibited scaling stochastic behaviours – in fact I would expect it. Unfortunately, if true, this makes accurate long term prediction of the climate far more difficult than we presently think it is and perhaps even impossible at the levels of variability we are interested in. That would certainly be a game changer.

  45. AJ


    I recall seeing a periodogram generated from the HadCRUT surface temperature data that pointed to a strong ~65yr cycle. I wonder what would be found if we did the same with the tidal guage data? Do you think that such an approach is valid?

  46. AJ


    I actually generated a periodogram on the Church and White data from 1930 to 2009. It indicates a 27yr and a 10yr cycle. As of 2009 we were at the top of both cycles. I wouldn’t be surprised if GSML trends drop markedly in the next few years. Then again, this could be completely spurious.

  47. AJ

    Actually, when I plot the detrended GMSL values, I can see why my periodogram is picking up a ~27 year cycle. The plot shows a 20mm drop between 1963 to 1965 and a 17mm drop between 1984 and 1988. This is about a 22yr cycle, so my thinking is that a periodogram can be somewhat ambiguous due to resolution issues. Maybe an astronomer, who is an expert in spectral analysis can set me straight. If history repeats itself though, we are due for another significant drop. Then again, as I said before, this could be completely spurious.

  48. jordan

    thank you for the info. So much crap out there !

  49. Bruce_in_San_Jose

    “…the imprint of global warming is still there, still real, and still affecting us all.”

    Warming as it has been doing since the last Ice Age. I am blown away by the selective publishing of data to support the Global Warming The Sky Is Falling agenda.

    First it is blamed on an increase of CO2 CAUSED BY MAN, even though data clearly shows that CO2 increases are the result of ocean warming, not the cause.

    Next, false data is widely distributed, with the UN and East Anglia being the relatively unchallenged sources. At every turn their media-distributed data is shown false by satellite photos of the ice pack, 40 years of satellite recorded surface temperature data, and most recently NASA’s additional data indicating CO2 levels appear to have no impact on re-radiation of earth’s heat. The theory of Global Warming is touted as “proved” every time there is a summer day temperature that goes a few degrees above average or there is a January “thaw” when an approaching cold front elicits south winds for a day or two. But, when average temps for the last ten + years hold steady or decline, it is just a “pothole” in the road to boiling seas and the death of Gaia (Mother Earth).

    In recorded history the earth has been much warmer. On a longer scale earth has been a frozen iceball. And, I am sorry to disappoint, but those fluctuations will continue irrespective and in spite of the presents of mankind.

  50. Bruce_in_San_Jose

    To emphasize my previous post, from a friend living in Platinum Alaska, I provide the following, which I am sure will be discounted as just an apocryphal story. But, certainly no more so than the “statistics” from the Global Warming/Weather Change crowd.

    “Earlier this fall Delta Western could not reach Nome Alaska to deliver fuel due to an early winter storm and the formation of Bering sea ice. Flying fuel into Nome will increase the cost three to four dollars per gallon. A Russian ice breaker will save about 50% of the shipping cost. The US Coast guard is in Vladivostok inspection a Russian ice breaker capable of breaking through 4 feet of ice to deliver the fuel. Once the ship has pass inspection it will depart for Korea to load the fuel for delivery to Nome.”

  51. @54. Bruce_in_San_Jose :

    Warming as it has been doing since the last Ice Age. I am blown away by the selective publishing of data to support the Global Warming The Sky Is Falling agenda. First it is blamed on an increase of CO2 CAUSED BY MAN, even though data clearly shows that CO2 increases are the result of ocean warming, not the cause.

    The data shows no such thing.

    Click on my name for a youtube clip debunking that particular canard.

    The natural processes caused by Milankovitch cycles are not at work this time here & climatologists have long since established that, yes, humans are to blame for this. I’d recommend you check out David Attenbrough’s youtube clip :

    Sir David Attenborough: The Truth About Climate Change

    For a great, short and effective demonstration of this.

  52. Hi:

    I was very interested in your math related to the GRACE map of excess water on the world’s continents. I did the math too, but in a different way. I loaded that image into a GIS, projected it onto a global equal-area map to reduce areal distortion, and converted it to a raster grid of equally sized cells.

    Then I calculated the net-wetness for the land. I summed up the mass values (positive or negative) over the land area to find the net positive or negative value. The final figure was positive, representing the increase in water mass over the year on the land.

    Then I distributed this net-wetness (the extra water globally on the map) onto the oceans and got a value of 2.4 mm. That is, if all the extra water on the land shown on that map were distributed over the oceans, it would make a layer of water 2.4 mm thick.

    The sea level drop reported is 6mm, so the water falling as rain or snow on the land in the GRACE map does not account for the 6mm drop in sea level.

    Your math went in reverse. You calculated the volume of the water ‘missing’ from the ocean and you distributed it over the land. But you never checked to see whether that depth of water on the land matched what the GRACE map shows.


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