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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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How much will sea levels rise in the 21st Century?

What the science says...

Select a level... Basic Intermediate

Sea levels are rising faster now than in the previous century, and could rise between 50cm to 1.5 metres by 2100

Climate Myth...

Sea level rise predictions are exaggerated

"Professor Niklas Mörner, who has been studying sea level for a third of a century, says it is physically impossible for sea level to rise at much above its present rate, and he expects 4-8 inches of sea level rise this century, if anything rather below the rate of increase in the last century. In the 11,400 years since the end of the last Ice Age, sea level has risen at an average of 4 feet/century, though it is now rising much more slowly because very nearly all of the land-based ice that is at low enough latitudes and altitudes to melt has long since gone." (Christopher Monckton)

Measuring Sea Levels

Sea levels are rising due to thermal expansion and melting of land-based ice. Global warming is causing the oceans to absorb a lot of extra heat (up to 90%). This makes the volume of water expand, and sea levels rise. The Greenland and Antarctic ice caps, and many of the world’s glaciers, are all slowly melting. The runoff feeds into rivers and directly into the oceans. This too adds to sea levels.

Prior to the use of satellite systems, measurements were taken using tide-gauges, devices that measure the height of a water level relative to a fixed point on land. Global estimates of sea level rise were subject to substantial differences in measurement from different parts of the world.

Sea levels change all the time. They are affected by seasons, astronomical tides, storm surges, currents and density, among other influences. Tidal gauges reflect these short term influences, introducing a large margin of error.

The IPCC Fourth Assessment Report described studies that estimated sea level rise for the 20th century between 0.5 and 3.0 mm a year. The most likely range, according to the IPCC, was between 1.0 and 2.0 mm a year.

Satellite altimetry since 1993 provides a more accurate measure of global sea level rise. Three different satellites take measurements: TOPEX/Poseidon (launched 1992), Jason-1 (launched 2001) and Jason-2 (launched 2008).

Figure 1: Source - CSIRO

The IPCC projections are derived from climate models. Using both tide gauge and satellite data, we can see that sea levels are rising. Unfortunately, sea level rise is already tracking the worst-case projections, as this graph shows:  

 

Figure 2: Sea level change. Tide gauge data are indicated in red and satellite data in blue. The grey band shows the projections of the IPCC Third Assessment report (Allison et al. 2009).

In fact, the climate models underestimated the rate of sea level rise because the rapid melting of the ice sheets and glaciers was not incorporated in the last IPCC report. (It was left out because the data were not considered sufficiently robust).

Damaging Potential

Rising sea levels are widely considered to be the greatest threat posed by climate change. They threaten low-lying countries with inundation, forcing inhabitants to migrate.  Coastal cities and ports could be flooded, as could cities sited near tidal estuaries, like London. Many nuclear installations are built by the sea so they can use sea water for cooling.

The potential for sea level rise is enormous. This is because the ice caps - Greenland and Antarctic - contain huge amounts of fresh water - around 70% of all the freshwater on Earth. Estimates suggest that if the Greenland ice sheet was to melt away to nothing, sea levels would rise around 6 metres. To put that a different way, a loss of just one per cent of the Greenland ice cap would result in a sea level rise of 6cm. 

If the West Antarctic Ice Sheet (WAIS) were to melt, this would add around 6 metres to sea levels. If the East Antarctic Ice Sheet (EAIS) were to melt as well, seas would rise by around 70 metres.

In a process that is accelerating, all three ice caps are losing mass. While nobody is suggesting any of the ice caps will melt away to nothing, only a small amount of melting would cause great problems.

A 1% loss of ice from these three sources would produce a likely increase in sea levels of around 76cm. With the thermal expansion implied by such melting, and contributions from melting glaciers, the oceans would actually rise far more.

Predictions for future sea levels

Future sea level rises depend on a number of factors. The amount of CO2 emitted will determine how much global warming takes place. The amount of ice that melts will vary according to the amount of global warming. The same is true of thermal expansion.

Previous estimates of sea level rise have been based on a set of possible outcomes called emissions scenarios. These theoretical scenarios range from emissions which fall very quickly, to emissions that continue to rise even faster than they have already. Scientists then calculate possible outcomes for each scenario.

In the next IPCC report (AR5), due in 2014, a new method has been used. Emission scenarios have been replaced by Representative Concentration Pathways (RCP). Four trajectories were chosen, based not on emissions, but possible greenhouse gas concentrations in the year 2100. From the concentrations, the RCPs project a ‘forcing’ for each pathway (the amount of warming); 2.6, 4.5, 6.0, and 8.5 Watts per metre squared. Each pathway is named after it’s forcing e.g. RCP4.5. The lowest emission scenario is also referred to as RPC3PD, because it posits a peak warming of 3 w/mby 2070 (~490 ppm CO2 and equivalents), and a reduction to 2.6 w/m2 by 2100. (PD stands for Peak/Decline). 

A draft version of the next report from the IPCC (AR5), due for publication in 2014, was recently leaked. Although the information is subject to change, the draft report says sea levels are likely to rise by between 29 and 82 centimeters by the end of the century, (compared to 18-59 centimeters in the 2007 report).

Other recent studies have projected comparable sea level increases. Jevrejeva (2011) for example modelled sea level rise using RPC scenarios. This table shows best and worst cases (RPC3PD and RCP8.5), with two in between. The figures for each projection are listed in this table:

Table 1: Projected sea level rise (m) by 2100 for the RCP scenarios. Results presented as median, upper (95% confidence interval) and lower (5% confidence interval) limits, calculated from 2,000,000 model runs. Sea level rise is given relative the period 1980–2000. (Jevrejeva 2011)

Another study (Rahmstorf 2011) obtained much the same results:

Figure 4: Sea level hindcasts and projections for different models calibrated with different temperature and sea level data. The error bars on the right indicate 90% confidence intervals (5–95 percentile, using the GISS temperature dataset); for the proxy-based projection the uncertainty is as presented in Kemp et al., 2011. (Rahmstorf 2011)

What's in the pipeline? 

The 'pipeline' is a term used to describe the slow reaction of the oceans to heating (inertia). Even if we were to stop emitting greenhouse gases tomorrow, the oceans would continue to rise, driven by the heat already stored. (90% of all the sun's energy falling on the surface of Earth is absorbed by the oceans as heat). This sea level rise is said to be 'in the pipeline'.

A paper published in PNAS - Levermann (2013) - has found that greenhouse gases emitted today will cause sea levels to rise for several centuries. For every degree of warming, sea levels will rise by more than 2 meters in the next few centuries. The Earth's temperature has already risen 0.8 degrees C over pre-industrial temperatures. 

Jevrejeva (2011) also found increased rates of sea level rise, even if emissions were to stabilise at 490 ppm by 2070 following the scenario in RPC3PD (RPC2.6):

Table 2: Projected sea level rise (m) by 2500 for the RCP scenarios. Results presented as median, upper (95% confidence interval) and lower (5% confidence interval) limits, calculated from 2,000,000 runs of the model. Values of sea level rise are given relative the period 1980–2000.

Conclusion

Based on the new mid-range IPCC  RCP4.5 scenario - around 650 ppm CO2 and equivalents producing a forcing of approximately 4.5 watts/metre - the most likely sea level rise by 2100 is betweem 80cm and 1 metre.  Longer term, sea levels will continue to rise even after emissions have been reduced or eliminated.

Basic rebuttal written by GPWayne


Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

This rebuttal was updated by Judith Matz on September 13, 2021 to replace broken links. The updates are a result of our call for help published in May 2021.

Last updated on 12 July 2015 by MichaelK. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

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Further viewing

From Peter Hadfield (potholer54 on YouTube) published on Dec 5, 2021

Compare two photos 130 years apart and it looks as though sea levels haven't moved. So why all the fuss about rising sea levels and evacuating islands? This video closes the yawning gap between internet myths and science.

Comments

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Comments 26 to 50 out of 102:

  1. Elsewhere wideEyedPupil comments:

    "Interested in comment from scientists on the Media watch story "AN ALARMING STORY" on 10 March about sea level rise, describing reportage of a 6 metre sea-level rise as alramist because they omitted the 4014 prediction-come-trueth date."

    The Media Watch (ABC, Australia) show has several problems, but arguably that is not one of them.  As can be seen from the main post above, expected sea level rises by the end of this century vary from 0.57 to 1.1 meters, depending on the scenario, with confidence intervals of 0.81 to 1.65 meters for the warmest scenario (table 1).  Those values are from a single study, and are higher than the IPCC values, who give a likely range of 0.45 - 0.82 meters for the warmest scenario by 2081-2100.  That is, its upper 66% confidence range almost coincides with the lower 95% confidence range of the study above.  I have heard several times that scientist making emperical projections of sea level rise think the IPCC relied to heavilly on models, and gave too low a value, but only a few expect sea level rises above 2 meters as even an upper bound.  Those few (best typified by Hansen), argue not that very high sea level rises are likely, but that they are possible, and sufficiently probable that they should be taken into account in establishing climate policy.  For what it is worth, I disagree with those very few, but several SkS regulars agree with them.

    Given that background, it is at minimum careless sensationalism to not mention the timescale involved, particularly given that a more or less specific time was given the the paper being reported on.

    Having said that, the Media Watch article is rife with inaccuracies itself.  To start with (and most germaine), the two thousand year interval in the study was chosen as a period in which equilibrium will have been reached.  That means they are predicting the sea level rise will be reached by 4014 AD, but do not specify that it will not be reached before than.  Potentially much before them.  In fact, while I consider it unlikely that the full sea level rise will be reached by 2100, it is certainly possible that it could be reached by 2500, and probable that it will reached by 3000 AD.  Indeed, technically the article does not preclude Hansen's worst fears being realized, and the full sea level rise being reached in as little as 150 to 200 years.  So, if leaving out the date is careless sensationalism, not specifying that the paper is stating the latest possible date for  the realization of sea level rise must be considered careless soft pedalling of a real threat.

    Even worse, is Media Watch's describing a 6.9 Meter rise in Sea Level as "a worst case scenario".  In fact, the paper in question mentions the number 6.9 exactly once.  In table 1 it shows as the median (not worst case) percentage of the current population displaced by sea level rise with a temperature of 3 C (again, not the worst case examined).  So it is neither a worst case, nor even a value for sea level rise.

    The actual values for sea level rise used in the paper comes from another paper from the same authors plus others.  That paper indicates a median sea level rise of 2.3 Meters per degree C increase in temperature.  It does not specify the error, but it is shown in figure Figure 2 E:

    The worst temperature case looked at in the original paper is a 5 C rise, and as can be seen, even with a 4 C rise, the worst case (95%) at even 4 C is well above 12 meters.  Even the median case at 5 C is an 11.5 meter sea level rise, so that Media Watch has stated as a worst case a value 40% less than the median value of the highest temperature examined.

    What is worse is that while 5 C is at the upper end of the likely range (66% confidence interval) for BAU (RCP 8.5) as given by the IPCC, that is just for warming until 2100.  By 2400 warming could procede well beyond that point so that 5 C may be the worst case examined, but it is not by any stretch of the imagination a worse case scenario.

    Consequently, while Media Watch's limited point is fair, in making it they have made far worse errors in the opposite direction - errors that in fact contradict the study they are reporting on rather than merely eliding ambiguous information.

    (Having looked at this, I will be notifying Media Watch of these issues.)

    Response:

    [RH] Tweaked image width.

  2. Has anyone encountered informaiton showing how much water is pushed to other parts of the ecosystem whenever there is a loss of rainforest, or deforestation in general, whether to desertification or increased agricultural/farming practices etc.. i.e. 130000 to 150000 km loss per year is a lot of moisture pushed into other parts of the planets storage capability! without having done the research I would imagine the quantity over the past 60 years is enough to skew the data?

    I only today read about the relationship of human pumping of groundwater to increased sea level rise. http://www.un-igrac.org/publications/422    snippet "because most of the groundwater released from the aquifers ultimately ends up in the world's oceans, it is possible to calculate the contribution of groundwater depletion to sea level rise. This turned out to be 0.8 mm per year, which is a surprisingly large amount when compared to the current sea level rise of 3.3 mm per years as estimated by the IPCC. It thus turns out that almost half of the current sea level rise can be explained by expansion of warming sea water, just over one quarter by the melting of glaciers and ice caps and slightly less than one quarter by groundwater depletion. Previous studies have identified groundwater depletion as a possible contribution to sea level rise. However, due to the high uncertainty about the size of its contribution, groundwater depletion is not included in the latest IPCC report. This study confirms with higher certainty that groundwater depletion is indeed a significant factor"

    This got me wondering about the ground biomass canopy and animal life storage capacity of the vast forest losses each year.

    Response:

    (Rob P) - See the SKS rebuttal: Sea level fell in 2010. There is a large year-to-year , and decadal-scale, exchange of water mass between the continents and ocean mainly due to rainfall patterns forced by La Nina & El Nino. The strong La Nina dominance over the last decade or so has stored greater-than-normal water mass on land. See Jensen (2013) - Land water contribution to sea level from GRACE and Jason-1 measurements & Baur (2013) - Continental mass change from GRACE over 2002–2011 and its impact on sea level - free copies are available online.

    This is part of the reason for the smaller-than-anticipated sea level rise in recent times - since the early 2000's anomalous water mass, equivalent to 0.2mm of sea level rise per year, has been stored on land. This is consistent with the increase in land vegetation (Net Primary Productivity) during that time. See: Bastos (2013) - The global NPP dependence on ENSO: La Niña and the extraordinary year of 2011

    No surprise that water availability impacts plant growth. But a return to El Nino-dominant conditions (the positive phase of the Interdecadal Pacific Oscillation) hints at major problems in the near-future. Sea level should rise more sharply too as the water mass drains from the continents.   

  3. Gary Marsh

    What the IGRAC page is missing is another change to the land water balance which is empoundment - the building of surface water storages. Some time back I read a study - I don't recall now where it was - that estimated the increase of surface water storage in dams etc. Serendipitously this roughly balances out the loss of groundwater.

     

  4. Glenn Tamblyn

    You are correct, I mistakenly thought the resevoir and surface water effect was taken into account in this study. The following article from the National Geographic News updates the information somewhat, whilst raising further points for consideration :)  http://tinyurl.com/NatGeo-Groundwater   It also mentions the forest effect, though having not found figures for this I am going to estimate an average of 1cubic metre height of water lost per square metre of forest/rainforest loss, to take into account water held in ground, biomass, roots, animals, above surface trees plants and atmospheric humidity, this would equal one cubic kilometre of water every 1000 kilometres of forest lost, times this by 130 000 square kilimetres lost per year = 130 cubic kilometres of extra water per year that ends up largely in the sea. I would apreciate informed comments as to how far off my estimations are and as to if there is any significance to this quantily of yeatly increase affecting sea level rise...   Mind you that last part I should be able to find out myself.. it's the per square kilometre water storage capacity of forest and attendents that are hard for me to assess.

  5. In case my last direct tinyurl link breaks, you can use this one but National Geographic will want you to sign in with email or facebook to read the article. http://news.nationalgeographic.com/news/2012/05/120531-groundwater-depletion-may-accelerate-sea-level-rise/?

    To sumarise a snip from the article referring to the work of a team of Dutch scientists led by hydrologist Yoshihide Wada 

    "Newly constructed reservoirs above ground can offset the net loss of water underground. These, Wada said, trap water that would otherwise reach the sea. Before 1990 or so, he added, that offset was large enough that the United Nations' Intergovernmental Panel on Climate Change never took groundwater depletion into account in predicting 21st-century sea-level rise. But that offset is no longer as significant as it once was, Wada said. "There are not so many places where people can build new reservoirs," he said. "They are already built."

    Already, he and his colleagues have found, groundwater depletion is adding about 0.6 millimeters per year (about one-fortieth of an inch) to the Earth's sea level. By 2050, he said, the triple pressures of growing population, economic development, and higher irrigation needs due to a warming climate will increase that to 0.82millimeters per year—enough to raise sea levels by 40 millimeters (1.6 inches) above 1990 levels. Between 2050 and 2100, according to some estimates, sea levels would rise even faster. To put that in perspective, he said, groundwater depletion adds about 25 percent to projected rates of sea-level rise, making it the largest contributor from land to sea-level rise other than the melting of the Greenland and Antarctic ice sheets. Even the melting of glaciers in the world's high mountains won't contribute more to rising sea levels, Wada said."

  6. BTW I can't see a facility to edit our posts, my last one double entried when my web browser had to "recover the webpage"...    sorry!

    Response:

    [JH] Your duplicate post has been deleted.

  7. Based on my estimation above (see 29.) 130 cubic kilometres of water directly lost each year to deforestation, spread over the world ocean surface of aproximatly 361 million square kilometres would equate to aproximately a 0.3mm rise per year, this allows for a percentage that would end up in rivers, reservoirs the atmosphere and the ground. I'm not a scientist or a skilled resercher so my quantities and sums must be checked, this is a significant figure so surely it is being accounted for somewhere and I'm just not finding it?

    Response:

    (Rob P) - No, the scenario you conjured up isn't accounted for. Not sure why this would surprise you given that you seem unwilling to read the scientific literature on sea level rise and provide zero supporting evidence for your scenario.  

  8. Gary Marsh @32, observations of the carbon budget show that plants represent a net sink of CO2, ie, that on average there is more plant matter on Earth at the end of each year than at the start.  That means that plants are an increasing reservoir of water rather than, as you would have it, a decreasing reservoir.  Absent other effects, the increase in net plant mass would tend to decrease sea level rise.

  9. Tom Curtis 33.   do you have a data source for year after year plant matter increase?

  10. Thanks for the responce, Tom. I forgot to come back and check up till now. There were three things that made me uncomfortable with the kind of (smug) over-confidence of the reportage:

    1. was the certainty that 6 metres would take 2000 for sure which was why I asked it here. Polar ice melt in Arctic has outstripped previous IPCC AR high sensativity senarios since positive feedbacks like melt water fluid dynamics wasn't included. Surge factors of storms at kingtide can have a SL rise multiplier effect up to even 100x, although presumably that's more about inland effected areas than actual rise on the land/sea edge.

    2. unknown timelines for under-researched 'methane burbping' of frozen gases in Arctic sea bed, tundra and Antarctic sea ice. Sensitivity of these gases to sea warming is somewhat in dispute and atmospheric GHG levels, and ocean warming pathways are still very much dependant on future human carbon intensive activity levels. The amounts of methane and COx stored frozen in these places dwarf the so-called remaining carbon budget of 565Gt (Meinshausen 2ºC concept). It's not clear to me the likely size or time of the earliest of these 'burps' but there is already wide columns of these gases rising into the atmosphere. It's not clear to me how much they would accelorate sea level rise.

    3. the most critical problem with the MW report was the (blyth) omission of the fact that while the Opera House may not see sandbagging/re-footing for well beyond a millenia the climatic tipping point that will guarenty that consequence is likely to be yesterday, today or some time in the next few decades (Kevin Anderson, Tyndal Climate Centre). So urgency is justified (in preference to scoffing). That certainly sents alarm bells ringing for me even if MW think they; have better things to think about in 2 thousand years. The consequence of that level of sea rise on cities and agriculture (in combination with a warmer more extreme climate) will be way more significant than the damages bill to the Opera House of course.

    Please comment on issue of climatic tipping points regards polar ice melt and attendant methane/COx leaking, Tom.

  11. Gary Marsh @34, the easiest one to consult is the IPCC:

    You will see that "Net Land Flux", ie, the balance between "Gross photosynthesis" and "Total respiration and fire" sequesters 2.6 +/-1.2 Petagrams C per annum.  From that we must subtract the 1.1 +/- 0.8 Petagrams emissions from "Net land use change" (which includes deforestation).  That yields a net sequestration of 1.5 +/- 1.44 Petagrams C per annum.  The uncertainty is at the 90% confidence level, indicating that there is a better than 95% chance that the net flux sequesters a small amount of CO2 annually, and a remote chance that the flux is effectively neutral.

    It should be noted that there has been a net reduction of the carbon reservoir in plants and soil of 30 +/- 45 Petagrams of Carbon, equivalent to approximately 15 ppmv.  It is therefore, likely that the net flux has not always sequestered CO2 over the last 264 years, but currently with tropical deforestation partially balanced by reforestation in the NH, and with the additional effects of CO2 fertilization, the reverse is the case.

  12. Tom Curtis  - It appears that the information you've provided from the IPCC is refferring to Carbon and CO2. The scenario I proposed for consideration concerns the direct transfer of H2O/water, it being a quicker and more direct contributer to sea level rise when it is released via deforestation, tropical and otherwise. I appreciate there are an enourmouse amount of variables to be considered when attempting to quantify the water holding capacity of the myriad types of forest, especially when factoring in attendent animal life from microble to mammal, the subterranian trunk and canopy and micro atmospherical climate which will hold significant quantities of water when forested and much less when deforested! add all these factors together and there will be a net movement of WATER. Although related this is a different process from the movement of Carbon, certainly it would appear to have a much more immediate effect. So again I ask if anyone can show me the data or studies if they even exist.

    Response:

    (Rob P) - You were provided with peer-reviewed literature in your comment @ 27, however you have not bothered to read any of it, or make any attempt to understand it.

    There has been a net growth in total biomass of land-plants over the recent decade, hence the uptake of carbon and water by plants has likewise grown.

    You are now in slogan-chanting territory and any further repetition of this meme, without any supporting evidence, will be deleted

  13. Gary Marsh @37, your initial premise is that there has been a reduction in plant mass.  That is shown to be false by the IPCC data.  If you now want to alter your premise by detailing water content of different sorts of plant mass, you need to actually provide detailed information on the relative water contents of different forms of plants, plus the relative growth or loss of those different plants.  You may then get an argument up that supports some measurable impact on sea level rise, (though I doubt it).  But if you don't do that legwork, you have nothing to discuss.  Your theory becomes "If all these complex and unmeasured factors come out just right, then changes in the biosphere are increasing sea level through loss of water."  To which is is sufficient to respond, "If they come out wrong, then you have the opposite, or no, effect".  The later is far more probably sight unseen than the former.  

  14. Looking at Post #5's Graph above, the 2006 peak is about 2mm below the 2011 valley. I would draw a new best fit curve starting in 2006 that shows an 8 mm rise in 6 years, or 1.33 mm/yr. With all that I've read lately about the cold 2012-13 and 2013-14 northern winters, I'd venture to say 2013 and 2014 would follow the 1.33 mm/yr line. Hardly the makings of flooding Florida, where I lived for 17 years in a house that is 14 feet above sea level. There's only so much water in the Olagalla aquifer, and when it is 70% empty in 2060, the rate of draw from it falls off a cliff. Then there's the huge increase in Great Lakes water levels this year. An unbelievable record increase in Lake Ontario and 14 inches added to Superior. Just Superior's gain offsets 7/33 of all land based melt from Antarctica. (cubic miles fraction for 1 year)

    Response:

    [JH] Please explain exactly how you did your "curve fitting" and provide the sources for the data that you have included in your post. Until you comply with this request, your future posts will be deleted.

  15. Jetfuel...your approach would almost certainly seriously underestimate the sealevels for 2012 and 2013 presented in the updated graph in the OP, since starting in 2006 looks like it would give you a steeper slope than the 3.2 mm /year overall average.  Which is why we don't draw regressions on small subsets of the data, especially cherrypicked ones.  Why would you take the trouble to go through the comments and ignore the updated graph anyway?  

    With regard to lake levels, there has been little net change in level of the Great Lakes over the time frame of the sealevel observations.  That includes this year.  You must be thinking about seasonal changes, but those are irrelevant to sea level change since they are ephemeral.  Also this year does not seem unusual when you look at the data.

    BTW moderators, the link to the updated version of the fisgure in comment 5 appears to be broken.

    Response:

    [DB] Fixed.

  16. jetfuel @39, Stephen Baines @40, here is the most recent update of sea level increase from the University of Colorado:

    As you can see, the trend from 1993 is still 3.2 mm per annum.  Clearly jetfuel's prediction of a trend of approximately 1.33 mm per annum is inaccurate.  I suspect Stephen Baines prediction of an increased trend since 2006 is also inaccurate, but that is not so obvious.  (It is more likely to have been accurate to early 2013 as in the OP.)

    Looking at the great lake data, Lake Ontario rose 0.11 meters between April 2013 and April 2014 inclusive, but fell 0.05 meters from May 2013 to April 2014, the actual one year "rise".  Even the former is no where near record breaking, being near one eigth the 0.86 meter rise from Dec 2012 to July 2013, although that does have a large seasonal component.  There have been larger seasonal and annual increases in the past. (For data, follow Stephen Baines' link.) 

  17. Thanks TC for the updated graph.  Yes I was referring to the trend line you would get from the graph in the OP.  It's not surprising that with more data you get reversion to the mean trend line.

    The recent large fluctuations around that mean trend are pretty interesting though.  I remember the decline was attributed to La Nina transporting water to temporary storage on land, but I haven't read anything really recent on that.  Even the large La Nina in 98-99 didn't have as big an effect.  I should look it up.

  18. Stephen, a significant part of the dip in 2011/12 ended up in Australia. Lake Eyre and several other lakes in Central Australia filled for the first time in years - flamingo heaven. Then slowly evaporated away over the next 2 years.

  19. jetfuel wrote: "Looking at Post #5's Graph above, the 2006 peak is about 2mm below the 2011 valley. I would draw a new best fit curve starting in 2006 that shows an 8 mm rise in 6 years, or 1.33 mm/yr."

    The human eye is only too good at finding patterns in noisy data, even when they don't actually exist.  That is why statisticians have invented methods for this problem, variously known as "breakpoint analysis", "broken stick regression", "segmented regression" etc.  What these methods do is determine whether the improvement in the fit of the model justifies the additional model complexity introduced by adding a breakpoint, which introduces at least two additional parameters to the model.

    If you don't follow standard statistical practice in this way and just pick the breakpoints by eye, you will generally end up overfitting the data and drawing meaningless conclusions based on the noise.  It is the sort of thing that is a recipe for confirmation bias.  So while you might do that, a scientist probably would know better.

  20. @ comment 5, is there any particular explanation for the drop in sea level circa 2011 in both the original graphic and the updated graphic? I looked up sunspots and there is some correlation but could that even make sense why it should?

     Are there any other explanations that work better?

  21. bozzza:

    www.skepticalscience.com/Extreme-Flooding-In-2010-2011-Lowers-Global-Sea-Level.html

  22. http://www.skepticalscience.com/sea-level-rise-predictions.htm 

    sorry....0.13 meters to 11.5 meters....so 35 feet...

    Response:

    [JH] Link activated.

  23. Rhoowl, assuming that this is in response to my comment here, given those specific values you are presumably referring to 'table 2' in the basic version of the article above. Of course, that table shows those two values as sea level rise by 2500 for two completely different emissions scenarios at opposite extremes of the uncertainty ranges... do you not have any idea what you are talking about here? Because that's the most charitable explanation I can think of for such a blatantly ridiculous argument.

  24. Rhoowl - Do you understand the difference between different emissions scenarios and the uncertainties (including modeled natural variation) for a single scenario? Your comment seems to indicate that you do not. 

  25. I have a slightly off-topic, but to me pressing question about the IPCC graph displayed in #36: The net land flux is shown to be increased by 2.6 +/- 1.2 PgC(arrow downwards), however the Vegetation reservoir became de(!)creased ( -30 +/- 45 PgC). I can't see were the additional 'land' Carbon is ending up. This seems inconsistent. Is there a missing number in the graph?

     

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