Sea Level Rise and Social Cost of Carbon

[Steven]

Does anyone have a good bead on what has been happening with the AMOC recently?

See website of the RAPID-MOC project:

http://www.rapid.ac.uk/rapidmoc/

[wili]

Thanks, Steven. My reactions went from 'Wow! Cool!" quickly to "Oh oh!"

25% (5 Sv) loss in volume in ten years!

At that rate, it will be gone in 30 years. I would presume that effects of a much slower current would be strongly felt long before that.

Why don't we hear more about the consequences of this weakening?

[AbruptSLR]

wili,

The following extract is from the RAPID - MOC website "Overview" tab:

Extract: "There is a northward transport of heat throughout the Atlantic, reaching a maximum of 1.3PW (25% of the global heat flux) around 24.5°N. The heat transport is a balance of the northward flux of a warm Gulf Stream, and a southward flux of cooler thermocline and cold North Atlantic Deep Water that is known as the meridional overturning circulation (MOC). The heat transported by the MOC is given off to the atmosphere and much of it is carried eastward by westerly winds. This is an important contribution to northwestern Europe's mild climate. Numerical models suggest that the MOC is likely to weaken by about 30% in the coming century as a consequence of greenhouse gas emissions."

Thus you can expect another 30% reduction in the AMOC by 2100, resulting in a continued high rate of RSLR for the US East Coast  through the end of the century, but do not expect a collapse of the AMOC.

Best,
ASLR

[LRC1962]

Apologies if discussed elsewhere.
Instead of stopping could it be possible we could see a similar occurrence with the ocean currents as we see with the jet streams. Some slow way down and get wavyer not following traditional paths and others pick up speed and get straighter. All this resulting in very cold spots and very very hot spots. Not only that but varying where the exact spots are over a long period of time. Somewhat like now but far more exaggerated. if this occurs then you could end up with even a worse situation where globally the average gets higher, but for any given local you could get extremes over the years from very low (relative to average) to extremely high and back to low.
In this scenario if a shipping port is in such a local how do you build the docks and infrastructure?
We can give anticipated averages even for a general location, but if ocean currents became far more unpredictable as the heated up oceans affect them, would it be possible to determine what SL would be on any given year even if we knew how fast SLR was occurring?

[wili]

Thanks, ASLR.

I still find it hard to believe that we will only see about the same amount of slowing over the whole rest of the century as we've seen in just the last ten years. Most trends don't seem to be slowing down like that--just the opposite.

I guess we'll see, or not.

[AbruptSLR]

Thanks, ASLR.

I still find it hard to believe that we will only see about the same amount of slowing over the whole rest of the century as we've seen in just the last ten years. Most trends don't seem to be slowing down like that--just the opposite.

I guess we'll see, or not.

wili,

Per the article in the linked website, the AMOC oscillates and since 2004 it has been on a downward cycle (see the attached image).  The 30% figure that I mentioned is the projected reduction in the AMOC by 2100 due to GHG that needs to be superimposed on top of the oscillations.

Best,
ASLR

http://www.eoearth.org/view/article/150290/

[Pmt111500]

US sea level north of New York City 'jumped by 128mm'
http://www.bbc.com/news/science-environment-31604953

Mmm... likely this would be a consequence of changing the downwelling area in the North Atlantic. The Gulf Stream (not the NA drift) operates as it has been (or somewhat slower and the cold from Nares (not from east Greenland) is enough to slow down the NA Drift so the warm water from Gulf of Mexico stack up here. A temporary effect at best imho, will drop some summer when the ice is out in the north.

[wili]

Thanks again, ASLR. I was wondering about whether there was some cyclicity going on here. That makes sense.

From your graph, though, it sure looks as though the periods when the AMO is on the positive side have gotten shorter through the century and a half, or so, of that record.

[Bruce Steele]

I think the combination of a very negative NAO 2009/2010 and the general decadal weakening of the AMOC resulting in 4 inches of anomalous sea rise is something to note . If that 2009/2010 window included a Sandy 4 inches of additional sea rise would do a lot of damage.
 From the following link " Note also that the winter 2009/2010 had the most negative NAO index measured during the almost 190 year record."

 http://www.cru.uea.ac.uk/~timo/datapages/naoi.htm

The premise that a strongly negative NAO in combination with weakened Atlantic meridional overturning resulting in predictably high tides should probably go into someones risk analysis planning.
?   

[AbruptSLR]

From your graph, though, it sure looks as though the periods when the AMO is on the positive side have gotten shorter through the century and a half, or so, of that record.

Also, the length of the PDO/IPO cycles are forecast (by climate models) to become shorter, as some scientists seem to think that we should not be entering the positive PDO phase that we entered last summer for another 4 to 5 years.  In a non-stationary climate it can be difficult to determine what is model signal vs model noise vs model bias.  Nevertheless, it is safe to say that we have already entered a period of increasingly extreme weather, annual, decadal, multi-decadal, and climatic events, all superimposed on top of each other and frequently working synergistically (in a chaotic manner).

As the ocean has at least 40 to 50-years of thermal inertia built-in (which affects: currents, prevailing wind patterns, barometric pressures, ice melting rates, storm surge & wave action), we are all guaranteed a wild ride for at least decades to come even if we both rapidly reduce GHG emissions and implement both Solar Radiation Management, SRM, and Negative Emissions Technology, NET, geoengineering.

[AbruptSLR]

For what it is worth, the attached is the AR5 RCP 4.5 mean SLR forecasts with steric, dynamic ocean and mean barometric pressure contributions but without dynamic ice melting contributions.

http://www.icdc.zmaw.de/ar5_slr.html?&L=1

Different sets of assumptions about contributions result in different forecasts.

[wili]

Thanks, ASLR. I can't figure out exactly what that last cool map is telling us besides that it looks like the NE coast of the US and Canada, along with most of coastal northern Europe look like they're in trouble.

Can you translate it into how many meters of SLR are predicted by when?

..............
WRT the earlier graph, here's a nice recent piece by M. Mann on oscillations and recent climate trends:

http://www.realclimate.org/index.php/archives/2015/02/climate-oscillations-and-the-global-warming-faux-pause/

[Steven]

"Numerical models suggest that the MOC is likely to weaken by about 30% in the coming century as a consequence of greenhouse gas emissions."

See also Section 12.4.7.2 of the IPCC AR5 report:

It is very likely that the Atlantic Meridional Overturning Circulation (AMOC) will weaken over the 21st century but it is very unlikely that the AMOC will undergo an abrupt transition or collapse in the 21st century. Best estimates and ranges for the reduction from CMIP5 are 11% (1 to 24%) in RCP2.6 and 34% (12 to 54%) in RCP8.5. There is low confidence in assessing the evolution of the AMOC beyond the 21st century. {12.4.7, Figure 12.35}

Caption of the above Figure:

Atlantic Meridional Overturning Circulation (AMOC) strength at 30°N (Sv) as a function of year, from 1850 to 2300 as simulated by different Atmosphere–Ocean General Circulation Models in response to scenario [RCP8.5]. The vertical black bar shows the range of AMOC strength measured at 26°N, from 2004 to 2011 {Figures 3.11, 12.35}

[AbruptSLR]

Thanks, ASLR. I can't figure out exactly what that last cool map is telling us besides that it looks like the NE coast of the US and Canada, along with most of coastal northern Europe look like they're in trouble.

Can you translate it into how many meters of SLR are predicted by when?

wili,

If you either move the slide bar on the image to the right, or if you click on the image, you will see the color code legend on the right side of the image showing that for the mean RCP 4.5 without dynamic ice melting contribution the regional SLR off of New England will "Likely" (i.e. with a 66% confidence interval) be about 0.3m by 2081−2100 with medium confidence i.e. assuming an ECS about 3 C; which is largely due to both ocean water warming and the slowdown of the AMOC (note that you would need to add ice melt contribution to get an actual forecast of RSLR).

Best,
ASLR

[Lennart van der Linde]

IPCC SLR projections not fit for coastal risk management:
http://www.eurekalert.org/pub_releases/2015-02/uos-isr022615.php

"The sea-level rise scenarios of the Intergovernmental Panel on Climate Change (IPCC) do not necessarily provide the right information for high-risk coastal decision-making and management, according to new research involving scientists from the University of Southampton.

A commentary, published today in the journal Nature Climate Change, warns that the IPCC scenarios are often inappropriate or incomplete for the management of high-risk coastal areas as they exclude the potential for extreme sea-level rises. This missing information is also crucial for a number of policy processes, such as discussions by G7 countries to establish climate insurance policies and allocations of adaptation funding by the Green Climate Funds."

[AbruptSLR]

The University of Colorado updated its global mean SLR curve on Feb 24 2015, with the latest data showing the influence of the currently strengthening Equatorial Kelvin Wave (or a possible forming El Nino event, which typically increases SLR above the average of the trend line):

[Laurent]

Flooding Google: Google's New Headquarters and the Threat of Sea-Level Rise
http://www.huffingtonpost.com/peter-h-gleick/flooding-google-googles-n_b_6804300.html?utm_hp_ref=green&ir=Green

[Sigmetnow]

Testing new housing designed for flood-prone areas.

http://www.reuters.com/article/2015/03/05/us-disaster-risk-architecture-idUSKBN0M100N20150305

[Laurent]

The tides they are a changin'
http://phys.org/news/2015-03-tides-changin.html

[Laurent]

Fast rise in sea level in 20 years, faster in Bengal
http://www.telegraphindia.com/1150307/jsp/nation/story_7331.jsp#.VPq9-s13_z8

[Laurent]

Climate change in the Marshall Islands and Kiribati, before and after – interactive
http://www.theguardian.com/environment/ng-interactive/2015/mar/11/climate-change-in-the-marshall-islands-and-kiribati-before-and-after-interactive

[AbruptSLR]

With a hat-tip to bassman (from the "2015 El Nino?" thread), I provide the accompanying image and link indicating that the global mean sea level rise trend line has surged upward in the past few months.  Possible causes include: (a) Net drought on land resulting in more water in the ocean; (b) a weak El Nino increasing the rainfall in the ocean; (c) increased ice melting; and (d) natural variability:

http://www.aviso.altimetry.fr/en/data/products/ocean-indicators-products/mean-sea-level.html

[RaenorShine]

With a hat-tip to bassman (from the ?2015 El Nino?" thread), I provide the accompanying image and link indicating that the global mean sea level rise trend line has surged upward in the past few months.  Possible causes include: (a) Net drought on land resulting in more water in the ocean; (b) a weak El Nino increasing the rainfall in the ocean; (c) increased ice melting; and (d) natural variability.

It is a fairy impressive upswing in SLR for 2014. I checked the data file on the site and there is a 8.9mm rise from the first reading of 2014 to the last one in the data set (Day 346) by my calculations. That's almost 3 times the average annual rise of 3.28mm indicated by the trend line.

[Lennart van der Linde]

Nice episode of VICE on HBO, featuring Eric Rignot on WAIS-collapse and showing effects of SLR in Bangladesh today:
https://www.youtube.com/watch?v=_h92Ath_2XA&feature=youtu.be

We need more of these.

[jai mitchell]

Thanks, Steven. My reactions went from 'Wow! Cool!" quickly to "Oh oh!"

25% (5 Sv) loss in volume in ten years!

At that rate, it will be gone in 30 years. I would presume that effects of a much slower current would be strongly felt long before that.

Why don't we hear more about the consequences of this weakening?

you do realize that once the arctic reaches a late September sea ice free state that this current will drop to near zero, right???

[wili]

jm, I don't follow you. Please explain.

[jai mitchell]

Wili,

The state change of going fro ice to ice-free conditions in august or even September will radically shift the temperature regimes in the arctic, this will cause significant surface warming.  This is going to produce a step-change reduction in the AMOC that will work against the inertia of the flow behind it to produce a piling up in the north atlantic

The model runs that steven used did not include the step-change effect of ice free conditions, but rather reflect a gradual increase in regional temperatures due to increased forcing.

[wili]

Thanks, jai. I guess I just hadn't thought through it that far.

[jai mitchell]

New Shindell Paper on the Social Cost of Carbon

http://link.springer.com/article/10.1007/s10584-015-1343-0

ABSTRACT

I present a multi-impact economic valuation framework called the Social Cost of Atmospheric Release (SCAR) that extends the Social Cost of Carbon (SCC) used previously for carbon dioxide (CO2) to a broader range of pollutants and impacts. Values consistently incorporate health impacts of air quality along with climate damages. The latter include damages associated with aerosol-induced hydrologic cycle changes that lead to net climate benefits when reducing cooling aerosols. Evaluating a 1 % reduction in current global emissions, benefits with a high discount rate are greatest for reductions of co-emitted products of incomplete combustion (PIC), followed by sulfur dioxide (SO2), nitrogen oxides (NOx) and then CO2, ammonia and methane. With a low discount rate, benefits are greatest for PIC, with CO2 and SO2 next, followed by NOx and methane. These results suggest that efforts to mitigate atmosphere-related environmental damages should target a broad set of emissions including CO2, methane and aerosol/ozone precursors. Illustrative calculations indicate environmental damages are $330-970 billion yr−1 for current US electricity generation (~14–34¢ per kWh for coal, ~4–18¢ for gas) and $3.80 (−1.80/+2.10) per gallon of gasoline ($4.80 (−3.10/+3.50) per gallon for diesel). These results suggest that total atmosphere-related environmental damages plus generation costs are much greater for coal-fired power than other types of electricity generation, and that damages associated with gasoline vehicles substantially exceed those for electric vehicles.

How much do you want to bet that he utilized the CMIP5 multi-model average to determine the damage loss estimates of sea level rise?  How much do you want to bet that his maximum sea level rise estimate by 2100 was .7 meters of sea level rise?

So, these values are only half of the values that they should be, based on that simple fact alone.

in the related article:  http://qz.com/355923/if-we-paid-for-the-hidden-cost-of-emissions-gas-would-be-6-25-a-gallon/

It says that gasoline should be 6.25 a gallon, Diesel should be 7.50 a gallon and goal electricity should be .30 cents per Kwh (it is .10 now)

As I said, the real values based on latest work are easily double this rate.

[AbruptSLR]

The authors of the linked reference corrected for the influence of the PDO and identified an anthropogenic SLR signal in the Tropical Pacific Ocean associated with warming of the Tropical Indian Ocean:

B. D. Hamlington, M. W. Strassburg, R. R. Leben, W. Han, R. S. Nerem & K-Y. Kim (2014), "Uncovering an anthropogenic sea-level rise signal in the Pacific Ocean", Nature Climate Change, 4,  782–785, doi:10.1038/nclimate2307

http://www.nature.com/nclimate/journal/v4/n9/full/nclimate2307.html

Abstract: "Internal climate variability across a range of scales is known to contribute to regional sea-level trends, which can be much larger than the global mean sea-level trend in many parts of the globe. Over decadal timescales, this internal variability obscures the long-term sea-level change, making it difficult to assess the effect of anthropogenic warming on sea level. Here, an attempt is made to uncover the sea-level rise pattern in the tropical Pacific Ocean associated with anthropogenic warming. More specifically, the sea-level variability associated with the Pacific Decadal Oscillation is estimated and removed from the regional sea-level trends computed from satellite altimetry measurements over the past two decades. The resulting pattern of regional sea-level rise uncovered in the tropical Pacific Ocean is explained in part by warming in the tropical Indian Ocean, which has been attributed to anthropogenic warming. This study represents one of the first attempts at linking the sea-level trend pattern observed by satellite altimetry to anthropogenic forcing."

[jai mitchell]

Agricultural Use of Groundwater as a Contributor to Sea Level Rise

http://www.motherjones.com/environment/2015/03/groundwater-pumping-sea-level-rise

"Long-term groundwater depletion represents a large transfer of water from the continents to the oceans," retired hydrogeologist Leonard Konikow wrote earlier this year in one article. "Thus, groundwater depletion represents a small but nontrivial contributor to SLR [sea-level rise]."

Makes sense: If you pull 20,000 year old subterranean water from the earth, it will eventually end up in the ocean.  As an added bonus, by drawing down the deep aquifers, the resident coastline will also subside, leading to an increased sea rise effect.

[AbruptSLR]

Here is another reference on the topic of groundwater depletion & SLR:

Wada, Y., L. P. H. van Beek, C. M. van Kempen, J. W. T. M. Reckman, S. Vasak, and M. F. P. Bierkens (2010), "Global depletion of groundwater resources", Geophys. Res. Lett., 37, L20402, doi:10.1029/2010GL044571.

http://onlinelibrary.wiley.com/doi/10.1029/2010GL044571/abstract

 Abstract: "In regions with frequent water stress and large aquifer systems groundwater is often used as an additional water source. If groundwater abstraction exceeds the natural groundwater recharge for extensive areas and long times, overexploitation or persistent groundwater depletion occurs. Here we provide a global overview of groundwater depletion (here defined as abstraction in excess of recharge) by assessing groundwater recharge with a global hydrological model and subtracting estimates of groundwater abstraction. Restricting our analysis to sub-humid to arid areas we estimate the total global groundwater depletion to have increased from 126 (±32) km3 a−1 in 1960 to 283 (±40) km3 a−1 in 2000. The latter equals 39 (±10)% of the global yearly groundwater abstraction, 2 (±0.6)% of the global yearly groundwater recharge, 0.8 (±0.1)% of the global yearly continental runoff and 0.4 (±0.06)% of the global yearly evaporation, contributing a considerable amount of 0.8 (±0.1) mm a−1 to current sea-level rise."

[wili]

http://www.ecoshock.net/downloads/ES_150325_Show.mp3

Kevin Anderson on a variety of climate topics.

[Sigmetnow]

A tiny step back from North Carolina's stance of "No Sea Level Rise Rate Increase allowed here, no sir."

The chairman of the state’s coastal planning board wants to let local towns and counties decide how North Carolina will cope with a rising sea level.

http://www.charlotteobserver.com/news/local/article17363684.html

[AbruptSLR]

The two linked references discuss the influence of uncertainties, regional conditions and initial oceanic conditions on long-term SLR projections.

Little, C.M., R.M. Horton, R.E. Kopp, M. Oppenheimer, and S. Yip, 2015: Uncertainty in twenty-first-century CMIP5 sea level projections. J. Climate, 28, no. 2, 838-852, doi:10.1175/JCLI-D-14-00453.1.

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00453.1

Abstract: "The representative concentration pathway (RCP) simulations included in phase 5 of the Coupled Model Intercomparison Project (CMIP5) quantify the response of the climate system to different natural and anthropogenic forcing scenarios. These simulations differ because of 1) forcing, 2) the representation of the climate system in atmosphere–ocean general circulation models (AOGCMs), and 3) the presence of unforced (internal) variability. Global and local sea level rise projections derived from these simulations, and the emergence of distinct responses to the four RCPs depend on the relative magnitude of these sources of uncertainty at different lead times. Here, the uncertainty in CMIP5 projections of sea level is partitioned at global and local scales, using a 164-member ensemble of twenty-first-century simulations. Local projections at New York City (NYSL) are highlighted. The partition between model uncertainty, scenario uncertainty, and internal variability in global mean sea level (GMSL) is qualitatively consistent with that of surface air temperature, with model uncertainty dominant for most of the twenty-first century. Locally, model uncertainty is dominant through 2100, with maxima in the North Atlantic and the Arctic Ocean. The model spread is driven largely by 4 of the 16 AOGCMs in the ensemble; these models exhibit outlying behavior in all RCPs and in both GMSL and NYSL. The magnitude of internal variability varies widely by location and across models, leading to differences of several decades in the local emergence of RCPs. The AOGCM spread, and its sensitivity to model exclusion and/or weighting, has important implications for sea level assessments, especially if a local risk management approach is utilized."


Jianjun Yin  (2015), "Long-term projection: Initializing sea level", Nature Climate Change, Volume: 5, Pages: 301–302, doi:10.1038/nclimate2589


http://www.nature.com/nclimate/journal/v5/n4/full/nclimate2589.html

Summary: "Long-term climate change and sea-level rise in model projections have been primarily determined by external forcing of climate conditions. Now, research shows that centennial projections of the dynamic sea level are also sensitive to the ocean's initial conditions."

[Sigmetnow]

How Flood Insurance Could Drive Americans From Coasts

The new paper, written by Moore and NRDC water official Becky Hayat, lays out one vision for how Congress could re-imagine the flood insurance program in two years, when it’s next due to be reauthorized.

Under their proposal, property owners would continue to receive discounts on their federal flood insurance coverage. In exchange, those owners would agree to not rebuild after their house is substantially damaged by a flood, and instead accept an offer from the government to purchase their property — for its pre-flood value.

http://www.climatecentral.org/news/flood-insurance-americans-on-coasts-18863

[jai mitchell]

you know, when the flood does come to south florida we are going to see a MASSIVE economic boost as hundreds of billions of dollars are spent disassembling infrastructure, lifting and relocating houses and producing whatever adaption responses are necessary for those sites that cannot be moved and must be protected for the next 20 years or so before they must ultimately be abandoned. 

So maybe the actual destruction of huge swaths of our currently inhabited regions are really an economic boon!

[AbruptSLR]

While the linked reference about observed accelerated rates of Elevation-Dependent Warming (EDW) has bad implications for many different topics, I post this here because accelerated EDW will continue to drive glacial ice melting that will contribute to SLR:

N. Pepin, R. S. Bradley, H. F. Diaz, M. Baraer, E. B. Caceres, N. Forsythe, H. Fowler, G. Greenwood, M. Z. Hashmi, X. D. Liu, J. R. Miller, L. Ning, A. Ohmura, E. Palazzi, I. Rangwala, W. Schöner, I. Severskiy, M. Shahgedanova, M. B. Wang, S. N. Williamson & D. Q. Yang (2015), "Elevation-dependent warming in mountain regions of the world", Nature Climate Change, doi:10.1038/nclimate2563

http://www.nature.com/nclimate/journal/v5/n5/full/nclimate2563.html

Abstract: "There is growing evidence that the rate of warming is amplified with elevation, such that high-mountain environments experience more rapid changes in temperature than environments at lower elevations. Elevation-dependent warming (EDW) can accelerate the rate of change in mountain ecosystems, cryospheric systems, hydrological regimes and biodiversity. Here we review important mechanisms that contribute towards EDW: snow albedo and surface-based feedbacks; water vapour changes and latent heat release; surface water vapour and radiative flux changes; surface heat loss and temperature change; and aerosols. All lead to enhanced warming with elevation (or at a critical elevation), and it is believed that combinations of these mechanisms may account for contrasting regional patterns of EDW. We discuss future needs to increase knowledge of mountain temperature trends and their controlling mechanisms through improved observations, satellite-based remote sensing and model simulations."

[RaenorShine]

Saw a comment on Robert Scribblers blog re a spike in sea level rise recently, just checked the numbers on AVISO and the late spike in 2014 has continued upwards.

http://www.aviso.altimetry.fr/en/data/products/ocean-indicators-products/mean-sea-level.html has the graph and also a link to the raw data.

The latest 2015 value (for day 50) shows a 2.8mm rise from the highest value of 2014 already this year (the rise is 3.3mm from the final value in 2014, and 8.7mm from a year ago).  We are almost 1cm above trend of 3.3mm per year, and looks to be close to record variablity from the graph.

[Lennart van der Linde]

The question is how we can seperate natural short-term sea level variability, on scales of months to over a year to a decade, from potential long term acceleration. For factors influencing short-term fluctuations:
http://en.wikipedia.org/wiki/Sea_level#Short_term_and_periodic_changes

From this plot it seems too early to say if there's an acceleration in the longer term trend:
http://sealevel.colorado.edu/content/2015rel1-global-mean-sea-level-time-series-seasonal-signals-retained

But sooner or later we do expect to see such an acceleration, so we keep watching out for the first signs...

[RaenorShine]

Lennart, agree entirely with your points, one high period doesnt make a trend (just as a low one does not mean a 'recovery').  It is very much still 'weather' rather than 'climate'. That doesn't mean we can't point the record data out though, just that we should be very careful about projecting forward from it.

The AVISO data is detrended for the regular annual and semi annual signals, but not as far as I can see for El Nino etc (see the peak in 1997-8). We'll have to see where this peak has come from in due course. The higher the peak goes the more likely a rebound dip comes on the other side (as in 1999).

It will take several years of higher rates to show a statistically significant shift. Just as with the recent global tempurature values it acts as a reminder of how we are changing the planet.

[Lennart van der Linde]

Some indications that SLR may have been accelerating over the past few years:
http://onlinelibrary.wiley.com/doi/10.1002/2015GL063902/abstract?utm_content=buffer63d49&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

"The global mean sea level (GMSL) was reported to have dropped 5 mm due to the 2010/11 La Niña and have recovered in one year. With longer observations, it is shown that the GMSL went further up to a total amount of 11.6 mm by the end of 2012, excluding the 3.0 mm/yr background trend. A reconciled sea level budget, based on observations by Argo project, altimeter and gravity satellites, reveals that the true GMSL rise has been masked by ENSO-related fluctuations and its rate has increased since 2010. After extracting the influence of land water storage, it is shown that the GMSL have been rising at a rate of 4.4 ± 0.5 mm/yr for more than three years, due to an increase in the rate of both land ice loss and steric change."

[Shared Humanity]

I've gotten myself in trouble before, talking about growth systems, but here I go again.

It does not surprise me in the least that there is evidence that SLR is accelerating. This acceleration will continue and I suspect we will be shocked by the annual SLR by mid century.

Why?

Most research studying the planets response to rising temperatures show that the processes that contribute to SLR are accelerating. Whether it is the speed of individual glaciers, ice mass loss for  GIS, WAIS and EAIS, or the temperature of the ocean, we are seeing these processes exhibit exponential behaviors. It is only logical that SLR, which is a result of these distinct processes,   would exhibit similar behaviors.

http://papers.risingsea.net/future-sea-level-rise.html

It is difficult to recognize these accelerations when you are relatively early in a growth pattern. This is especially true when you are dealing with a huge initial stock such as the volume of the ocean waters which has processes that cause SLR to naturally fluctuate. Be patient, the exponential growth behavior will become quite obvious within a decade and the annual gains will eventually dwarf any natural fluctuations in sea level.

The effect will be that we are going to spend the century continuously astonished by how rapid the seas rise.

Our expectations will always be, quite literally, behind the curve.

I do not know if this chart accurately reflects current IPCC estimates for SLR (I believe it was published in 2007.) but the instrumental record clearly suggests an exponential growth pattern. I expect actual SLR to be above the upper boundary of estimates, significantly above as the growth of the contributing processes continue to accelerate.

[Shared Humanity]

Once we recognize that a particular process is a growth process, it is relatively easy to project the future as it becomes a simple math problem. We first need to determine the doubling rate. How much time has it taken for the growth in SLR to double? Once we have made this calculation, we simply need to calculate the future rise by doubling the rate of growth of SLR through the end of the century.

[Laurent]

The problem is that the doubling rate is also decreasing, it won't be so simple to calculate...what are we waiting for anyway just 50 cm of SLR is dramatic for many coastal regions !?

[Shared Humanity]

The problem is that the doubling rate is also decreasing, it won't be so simple to calculate...what are we waiting for anyway just 50 cm of SLR is dramatic for many coastal regions !?

Yes.

The source of most of our surprise is that we confuse stocks and flows in a growth system. All growth systems consist of stocks and flows. SLR is actually a measure of stock in the system, the aggregate volume of the oceans. These stocks grow exponentially due to the flows that feed the stock. EAIS volume loss is a flow. WAIS volume loss is a flow. GIS volume loss is a flow. These volume losses are contributing to the accelerating  growth in the stock (again, the aggregate volume of  the oceans).

This is no different than what we find when we invest or save money. If we are receiving a 3% return on our investments and savings (the flow) we will see an exponential growth rate in our wealth (the stock).

Unless someone can show me where the volume losses will stop or slow significantly, we should expect the current doubling rate of our wealth the aggregate volume of  the oceans) to  continue. If any of the flows (EAIS, WAIS or GIS ice sheet volume losses) are growing, then the doubling time for growth in the stock will shorten.

[AbruptSLR]

The problem is that the doubling rate is also decreasing, it won't be so simple to calculate...what are we waiting for anyway just 50 cm of SLR is dramatic for many coastal regions !?

Yes.

The source of most of our surprise is that we confuse stocks and flows in a growth system. All growth systems consist of stocks and flows. SLR is actually a measure of stock in the system, the aggregate volume of the oceans. These stocks grow exponentially due to the flows that feed the stock. EAIS volume loss is a flow. WAIS volume loss is a flow. GIS volume loss is a flow. These volume losses are contributing to the accelerating  growth in the stock (again, the aggregate volume of  the oceans).

This is no different than what we find when we invest or save money. If we are receiving a 3% return on our investments and savings (the flow) we will see an exponential growth rate in our wealth (the stock).

Unless someone can show me where the volume losses will stop or slow significantly, we should expect the current doubling rate of our wealth the aggregate volume of  the oceans) to  continue. If any of the flows (EAIS, WAIS or GIS ice sheet volume losses) are growing, then the doubling time for growth in the stock will shorten.

SH,

As you can see from scanning through earlier posts in this thread, that Hansen & Sato (2012) have already done what you suggest and instead of finding a maximum SLR by 2100 of 0.5m (per AR4); they estimated that the maximum SLR value by 2100 could likely be about 5m (see the first attached image).

Nevertheless, NOAA (who is the USA's primary science advisor to policy makers on SLR) chose to ignore Hansen & Sato (2012) in their December 2012 SLR guidance, where instead they used the 2008 maximum SLR values give by Pfeffer et al as I have noted on the second attached image of the 2012 NOAA- Parris SLR guidance that gives policy makers four curves to choose from, with the lowest curve assuming a linear rate of SLR 1.7 mm/yr through 2100, and the highest curve projecting 2m of SLR by 2100.  This illustrates that we currently live in the Anthropocene Era where much of the public and many of the policy makers feel entitled to choose what to accept how the Earth Systems will respond to continued radiative forcing; which is why the CoP21 national contributions to control GHG emissions are voluntary.

I concur that in the next decade of two that it will become more difficult to ignore high Earth System responses to continued radiative forcing; but in the meantime you should be aware that IPCC SLR model projections are probably one of the least accurate projections in AR5 (which are about 50% higher than for the AR4 SLR projections that you posted).

Best,
ASLR

[Shared Humanity]

Thanks ASLR. You, and others, post so much great material here that I am able to read only a small portion of  the research and understand only a portion of that. It does not surprise me that extensive research has already been done to either confirm or completely refute  any comment I make. It also doesn't surprise  me that this research is linked  above.

Keep it  coming. I am learning.

[AbruptSLR]

SH,

The linked article presents two figures that elucidate the IPCC's thinking in AR5 SLR projections (see attached images & associated captions); which show how much they increased their SLR projections compared to the AR4 image that you posted.  However, the Oct 2014 ThinkProgress article also cite research published after the AR5 cut-off date indicating the the SLR contribution from the Antarctic, and Greenland, Ice Sheets will likely be considerably higher than assumed in AR5; and since the Oct 2014 ThinkProgress article a significant number of papers have been published indicating the SLR contribution from the West Antarctic Ice Sheet could be over 2m by 2100 if we stay on a BAU pathway (see the link at the bottom of this post for discussion on this matter):

http://thinkprogress.org/climate/2014/10/16/3580131/worst-case-sea-level-rise/

Caption Figure 1: "Projected component of global sea level rise by 2100 relative to 2000 and their uncertainty. Vertical light grey bars indicate the 5, 50 and 95th percentiles in the uncertainty distribution. Dark grey bars represent projected sea level components calculated in this study. Thick red lines show the likely range of the sea level contributions from the AR5 and red thin lines are our fit to the AR5 distribution."

Caption Figure 2: "Projected global mean sea level rise by 2100 relative to 2000 for the RCP8.5 scenario and uncertainty. Vertical grey bars indicate the 5, 17, 50, 83, and 95th percentiles in the uncertainty distribution."

http://forum.arctic-sea-ice.net/index.php/topic,31.350.html

Best,
ASLR

[sidd]

Hansen chimes in on an Australian radio:

"The ice sheets are losing mass faster and faster with a doubling the of about 10 years. If that continues, we would get sea-level rises of several metres within 40 to 50 years."

http://rabett.blogspot.com/2015/05/why-jim-hansen-worries.html

and
http://www.abc.net.au/radionational/programs/breakfast/two-degrees-of-global-warming-is-not-safe/6444698