Sea Level Rise Projections

8/2/2019 Sea Level Rise Projections

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sea-level riseThe case for a 2-metre standard

climatecodered.orgmarch 2012


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Sea-level rise

projectionsThe case for a 2-metre to 2100

standardCompiled by David Sprattwww.climatecodered.org

AUSTRALIAN GOVERNMENT

Recent research, presented at the Copenhagen Climate Congress in March2009, projected sea-level rise from 0.75 to 1.9 metres relative to 1990, with1.11.2 metres the mid-range of the projection.

Source: Climate Change Risks to Australia's Coasts: A first pass nationalassessment, Australian Government, Canberra, November 2009

Sea-level rise larger than the 0.51.0 m range perhaps towards 1.5 m(i.e. at the upper range of the statistical projection of Rahmstorf 2007) cannot be ruled out. There is still considerable uncertainty surroundingestimates of future sea-level rise. Nearly all of these uncertainties, however,operate in one direction, towards higher rather than lower estimates Oneof the more dramatic consequences of modest increases in sea level is thedisproportionately large increase in the frequency of extreme sea-level eventsassociated with high tides and storm surges. A 0.5 m rise in mean sea-levelcould cause such extreme events to occur hundreds of times more frequentlyby the end of the century; an event that now happens once every hundredyears would be likely to occur two or three times per year.

Source: "Climate Change 2009: Faster change & more serious risks",

W. Steffen, Australian Government, Canberra, May 2009

Current estimates ofsea-level rise range from 0.50 m to over 2 m by2100.

Source: Science Update 2009: November (issue 2), CSIRO/BoM/Department of Climate Change, November 2009

Geological data indicate sea levels several metres above todays value, andaverage rates of sea-level rise of 1.6 m/century, at a time when globalaverage temperature was similar to projections for the end of the 21stcentury. These results show that a change in sea level more rapid thanpresent projections is credible and has occurred before.


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Source: Briefing: A Post IPCC AR4 Update on Sea-Level Rise, Church,White, Hunter and Lambeck, ACE CRC/CSIRO/ANU/AAS, 2008

VICTORIAN GOVERNMENT

Several new estimates of sea level rise in the 21st century, which includenew information on melting ice, have been published since the release of theIPCC report in 2007. These increases vary from 50 centimetres to up to 2metres by 2100.

Source: Understanding sea level rise and climate change, DSE Factsheet, Victorian Government, Melbourne, June 2011

PEER-REVIEWED SCIENCE

"On the basis of calculations presented here, we suggest that an improvedestimate of the range of SLR to 2100 including increased ice dynamics liesbetween 0.8 and 2.0 m. these values give a context and starting point forrefinements in SLR forecasts on the basis of clearly defined assumptions andoffer a more plausible range of estimates than those neglecting the dominantice dynamics term.

Source: Kinematic Constraints on Glacier Contributions to 21st-CenturySea-Level Rise, Pfeffer et al., Science, 321: 1340-1343.

For future global temperature scenarios of the Intergovernmental Panel onClimate Change's Fourth Assessment Report, the relationship projects a sea-level rise ranging from 75 to 190 cm for the period 19902100.

Source: Global sea level linked to global temperature, Vermeer andRahmstorf, PNAS, 106:21527-21532

The range of future climate-induced sea-level rise remains highly uncertainwith continued concern that large increases in the twenty-first century cannotbe ruled out. The biggest source of uncertainty is the response of the largeice sheets of Greenland and west Antarctica. Based on our analysis, apragmatic estimate of sea-level rise by 2100, for a temperature rise of 4C ormore over the same time frame, is between 0.5m and 2m the probabilityof rises at the high end is judged to be very low, but of unquantifiableprobability Climate-induced rise of relative sea level during the twenty-firstcentury could be larger than the widely reported absolute numbers publishedby the IPCC AR4, and a rise of up to 2m is not implausible but ofunquantifiable probability.

Source: Sea-level rise and its possible impacts given a 'beyond 4C world'

in the twenty-first century, Nicholls, Marinova et al., Phil. Trans. R. Soc. A2011 369: 161-181


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A NOTE ON IPCC 2007

The 2007 ICC Fourth Assessment Report projections on sea-level rise of18-59 cms to 2100 were far too low because they did not make any allowancefor melting of the polar icecaps. The IPCC report contained the followingqualification: Because understanding of some important effects driving sea-level rise is too limited, this report does not assess the likelihood, nor providea best estimate or an upper bound for sea level rise. It added that the officialprojected sea-level rise of 1859 centimetres this century did notinclude uncertainties in climate-carbon cycle feedbacks nor the fulleffects of changes in ice sheet flow, therefore the upper values of theranges are not to be considered upper bounds for sea level rise.

The relationship between the IPCC projections and more recent research isillustrated in Figure 1, adapted from Sea-level rise and its possible impactsgiven a 'beyond 4C world' in the twenty-first century, Nicholls, Marinova et al.,Phil. Trans. R. Soc. A 2011 369: 161-181

A 2009 study by Siddall et al. which suggested a sea-level rise of only 782cms to 2100 (consistent with IPCC 2007), was withdrawn due to technical


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errors.

Source: Constraints on future sea-level rise from past sea-level change,Siddall, Stocker et al., Nature Geoscience 2, 571 - 575

http://www.guardian.co.uk/environment/2010/feb/21/sea-level-geoscience-retract-siddall

SEA-LEVEL RISE FROM ICE-SHEET LOSS IS A NON-LINEAREVENT, BUT RATE OF POLAR ICE MASS LOSS IS INCREASING

Ice sheet disintegration is nonlinear, spurred by amplifying feedbacks. Wesuggest that ice sheet mass loss, if warming continues unabated, will becharacterized better by a doubling time for mass loss rate than by a lineartrend. Satellite gravity data, though too brief to be conclusive, are consistentwith a doubling time of 10 years or less, implying the possibility of multi-metersea level rise this centurySea level rise, despite its potential importance, is one of the least wellunderstood impacts of human-made climate change. The difficulty stemsfrom the fact that ice sheet disintegration is a complex non-linearphenomenon that is inherently difficult to simulate, as well as from theabsence of a good paleoclimate analogue for the rapidly increasing human-made climate forcing.

Source: Hansen and Sato, Paleoclimate implications for human-madeclimate change in Climate Change: Inferences from Paleoclimate andRegional Aspects. Berger, Mesinger and ijai (Eds) Springer, in press,http://arxiv.org/abs/1105.0968v3

However, it is difficult for us to say how long it will take ice sheets torespond to human-made climate forcing because there are no documentedpast changes of atmospheric CO2 nearly as rapid as the current human-made change.

Source: Earth's Climate History: Implications for Tomorrow, Hansen andSato, http://www.giss.nasa.gov/research/briefs/hansen_15/PaleoImplications.pdf

Pulses of extra melting and uplift imply that well experience pulses of extrasea level rise The process is not really a steady process.

Source: 2010 spike in Greenland ice loss lifted bedrock, GPS reveals, OhioState University Research, 9 December 2011, http://researchnews.osu.edu/archive/greenlift.htm

We use monthly measurements of time-variable gravity from the GRACEsatellite gravity mission to determine the ice mass-loss for the Greenland and

Antarctic Ice Sheets during the period between April 2002 and February 2009.We find that during this time period the mass loss of the ice sheets is not aconstant, but accelerating with time, i.e., that the GRACE observations arebetter represented by a quadratic trend than by a linear one, implying that the
http://researchnews.osu.edu/archive/greenlift.htmhttp://researchnews.osu.edu/archive/greenlift.htmhttp://www.giss.nasa.gov/research/briefs/hansen_15/PaleoImplications.pdfhttp://www.giss.nasa.gov/research/briefs/hansen_15/PaleoImplications.pdfhttp://arxiv.org/abs/1105.0968v3


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ice sheets contribution to sea level becomes larger with time.

Source: Increasing rates of ice mass loss from the Greenland and Antarcticice sheets revealed by GRACE, Velicogna, Geophys. Res. Lett., 36:L19503,

Many glaciers along the margins of the Greenland and Antarctic icesheets are accelerating and, for this reason, contribute increasingly toglobal sea-level rise. Globally, ice losses contribute ~1.8mm/yr, but thiscould increase if the retreat of ice shelves and tidewater glaciers furtherenhances the loss of grounded ice or initiates the large-scale collapse ofvulnerable parts of the ice sheets. Ice loss as a result of accelerated flow,known as dynamic thinning, is so poorly understood that its potentialcontribution to sea level over the twenty-first century remains unpredictable.

Source: Extensive dynamic thinning on the margins of the Greenland and

Antarctic ice sheets, Pritchard, Arthern et al., Nature 461:971-975

THE PALEOCLIMATE RECORD: PAST RAPID SEA LEVEL RISES

The peak rate of deglaciation following the last Ice Age was about onemeter [39 inches] of sea-level rise every 20 years, which was maintainedfor several centuries.

Source: Defusing the Global Warming Time Bomb, Dr James Hansen(Director NASA Goddard Institute for Space Studies), Scientific American,

March 2004

Note: A study of the Eemain (about 120,000 years ago) is important andgives an insight into conditions later this century, because during the Eemianthe global mean temperature was less than 1C higher than today (Hansenand Sato, Paleoclimate implications for human-made climate change inClimate Change: Inferences from Paleoclimate and Regional Aspects.Berger, Mesinger and ijai (Eds) Springer, in press.) A study by Rohling etal concludes:

We find average rates of sea-level rise of 1.6 m per century (during thelast interglacial period 124 to 119 thousand years ago) with a full potentialrange for the rates of rise between 2.5 and 0.6 m per century As globalmean temperatures during (this period) were comparable to projections forfuture climate change under the influence of anthropogenic greenhouse-gasemissions, these observed rates of sea-level change inform the ongoingdebate about high versus low rates of sea-level rise in the coming century.

Source: High rates of sea-level rise during the last interglacial period,Rohling, Grant et al, Nature Geoscience 1, 38 - 42 (2008)

Note: Another study of the Eemian by Blancon et. al, examining thepaleoclimate record, shows sea level rises of 23 metres in 50 years due to
http://www.nature.com/ngeo/journal/v1/n1/full/ngeo.2007.28.html#a1


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the rapid melting of ice sheets 120,000 years ago.

The abrupt demise of the lower-reef crest, but continuous accretion betweenthe lower-lagoonal unit and the upper-reef crest, allows us to infer that thisback-stepping occurred on an ecological timescale and was triggered by a 2

3-m jump in sea level.

Source: Rapid sea-level rise and reef back-stepping at the close of the lastinterglacial highstand, Blanchon, Eisenhauer et al., Nature 458:881-884

LONGER TERM CONSEQUENCES OF TODAYS GREENHOUSE GASLEVELS FOR SEA LEVELS

Even if we would curb all CO2 emissions today, and stabilise at the modernlevel (387 parts per million by volume), then our natural relationship suggeststhat sea level would continue to rise to about 25 metres above the present

Source: Antarctic temperature and global sea level closely coupled overthe past five glacial cycles, Rohling, Grant et al., Nature Geoscience2:500-504

We know that [when] CO2 was around 400 or 450 parts per million in theatmosphere...there was no ice sheet on West Antarctica...Thats where werealmost at now.

Source: Obliquity-paced Pliocene West Antarctic ice sheet oscillations,

Naish, Powell et al., Nature 458: 322

The last time carbon dioxide levels were apparently as high as they aretoday and were sustained at those levels global temperatures were 5 to10 degrees Fahrenheit higher than they are today, the sea level wasapproximately 75 to 120 feet higher than today, there was no permanent seaice cap in the Arctic and very little ice on Antarctica and Greenland.

Source: Aradhna Tripati, UCLA speaking (http://www.newsroom.ucla.edu/portal/ucla/last-time-carbon-dioxide-levels-111074.aspx) on release ofCoupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of

the Last 20 Million Years, Tripadi, Roberts et al., Science 326: 1394-1397

March 2012
http://www.newsroom.ucla.edu/portal/ucla/last-time-carbon-dioxide-levels-111074.aspxhttp://www.newsroom.ucla.edu/portal/ucla/last-time-carbon-dioxide-levels-111074.aspxhttp://www.nature.com/nature/journal/v458/n7240/abs/nature07933.html#a1

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