THIS POST IS A PRESENTATION OF SEA LEVEL RISE FORECASTS AND THE INTERPRETATION OF THE UNCERTAINTY IN THESE FORECASTS BY CLIMATE SCIENCE WITH THE RELEVANT BIBLIOGRAPHY PROVIDED.

RELATED POSTS ON THE WAY CLIMATE SCIENCE INTERPRETS UNCERTAINTY IN THEIR FORECASTS:

LINK#1: https://tambonthongchai.com/2018/05/22/global-warming-science-2007-the-dearth-of-scientific-knowledge-only-adds-to-the-alarm/ LINK#2: https://tambonthongchai.com/2019/12/12/methanescare/ LINK#3: https://tambonthongchai.com/2019/11/03/lessweknow/ LINK#4: https://tambonthongchai.com/2019/11/03/lessweknow/

QUESTION: HOW MUCH SEA LEVEL RISE WILL ANTHROPOGENIC GLOBAL WARMING CAUSE BY THE YEAR 2100 IF WE DON’T TAKE CLIMATE ACTION?

ANSWER: PROJECTED SEA LEVEL RISE FOR THE YEAR 2100: THE LESS WE KNOW THE SCARIER IT GETS AND SO THE LESS WE KNOW THE MORE YOU NEED TO CUT FOSSIL FUEL EMISSIONS. {THE RELEVANT BIBLIOGRAPHY}

1. CHURCH 2013 45 to 98 cm: Church, John A., et al. “Sea-level rise by 2100.” Science 342.6165 (2013): 1445-1445. AR5 by Working Group I (WGI) of the IPCC (“A Stronger IPCC Report,” 4 October, p. 23), R. A. Kerr highlights three fundamental conclusions about climate change that were assessed with equal or greater confidence than in previous IPCC reports. He also points to three “contentious points” on which he states that the AR5 “took a moderate line.” Kerr includes sea-level projections among these points, and reports “a rise of 40 to 60 centimeters by late in the century and a worst case of 1 meter by 2100, [which is] higher than in 2007 but far below the meter or two of sea-level rise that some expect. As the authors of the IPCC WGI AR5 chapter on “Sea-Level Change,” we wish to clarify that for the highest emission scenario considered (RCP8.5), the AR5 reported a likely range of 45 to 82 cm for sea-level projections for the late 21st century (average over 2081 to 2100) and of 52 to 98 cm by 2100. The difference in sea level between these two periods is large because in 2081 to 2100, the likely rate of rise is 8 to 16 mm per year, which is up to about 10 times the average rate of rise during the 20th century
2. RAHMSTORF 2007 50 TO 140 cm: Rahmstorf, Stefan. “A semi-empirical approach to projecting future sea-level rise.” Science 315.5810 (2007): 368-370. A semi-empirical relation is presented that connects global sea-level rise to global mean surface temperature. It is proposed that, for time scales relevant to anthropogenic warming, the rate of sea-level rise is roughly proportional to the magnitude of warming above the temperatures of the pre–Industrial Age. This holds to good approximation for temperature and sea-level changes during the 20th century, with a proportionality constant of 3.4 millimeters/year per °C. When applied to future warming scenarios of the Intergovernmental Panel on Climate Change, this relationship results in a projected sea-level rise in 2100 of 50 to 140 cm above the 1990 level.
3. PFEFFER 2008 80 to 200 cm: Pfeffer, W. Tad, Joel T. Harper, and Shad O’Neel. “Kinematic constraints on glacier contributions to 21st-century sea-level rise.” Science 321.5894 (2008): 1340-1343. On the basis of climate modeling and analogies with past conditions, the potential for multimeter increases in sea level by the end of the 21st century has been proposed. We consider glaciological conditions required for large sea-level rise to occur by 2100 and conclude that increases in excess of 2 meters are physically untenable. We find that a total sea-level rise of about 2 meters by 2100 could occur under physically possible glaciological conditions but only if all variables are quickly accelerated to extremely high limits. More plausible but still accelerated conditions lead to total sea-level rise by 2100 of about 0.8 meter. These roughly constrained scenarios provide a “most likely” starting point for refinements in sea-level forecasts that include ice flow dynamics. 80 to 200 cm.
4. HORTON 2014: 40 TO 120 cm: Horton, Benjamin P., et al. “Expert assessment of sea-level rise by AD 2100 and AD 2300.” Quaternary Science Reviews 84 (2014): 1-6. Large uncertainty surrounds projections of global sea-level rise, resulting from uncertainty about future warming and an incomplete understanding of the complex processes and feedback mechanisms that cause sea level to rise. Consequently, existing models produce widely differing predictions of sea-level rise even for the same temperature scenario. Here we present results of a broad survey of 90 experts who were amongst the most active scientific publishers on the topic of sea level in recent years. They provided a probabilistic assessment of sea-level rise by AD 2100 and AD 2300 under two contrasting temperature scenarios. For the low scenario, which limits warming to <2 °C above pre-industrial temperature and has slowly falling temperature after AD 2050, the median ‘likely’ range provided by the experts is 0.4–0.6 m by AD 2100 and 0.6–1.0 m by AD 2300, suggesting a good chance to limit future sea-level rise to <1.0 m if climate mitigation measures are successfully implemented. In contrast, for the high warming scenario (4.5 °C by AD 2100 and 8 °C in AD 2300) the median likely ranges are 0.7–1.2 m by AD 2100 and 2.0–3.0 m by AD 2300, calling into question the future survival of some coastal cities and low-lying island nations.
5. MEIER 2007: 10-25cm more than estimates in the literature: Meier, Mark F., et al. “Glaciers dominate eustatic sea-level rise in the 21st century.” Science 317.5841 (2007): 1064-1067. Ice loss to the sea currently accounts for virtually all of the sea-level rise that is not attributable to ocean warming, and about 60% of the ice loss is from glaciers and ice caps rather than from the two ice sheets. The contribution of these smaller glaciers has accelerated over the past decade, in part due to marked thinning and retreat of marine-terminating glaciers associated with a dynamic instability that is generally not considered in mass-balance and climate modeling. This acceleration of glacier melt may cause 0.1 to 0.25 meter of additional sea-level rise by 2100.
6. JEVREJEVA 2014: The upper limit is 180cm: Jevrejeva, Svetlana, Aslak Grinsted, and John C. Moore. “Upper limit for sea level projections by 2100.” Environmental Research Letters 9.10 (2014): 104008. We construct the probability density function of global sea level at 2100, estimating that sea level rises larger than 180 cm are less than 5% probable. An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica. This leads to an intrinsically hard to quantify fat tail in the probability distribution for global mean sea level rise. Thus our low probability upper limit of sea level projections cannot be considered definitive. Nevertheless, our upper limit of 180 cm for sea level rise by 2100 is based on both expert opinion and process studies and hence indicates that other lines of evidence are needed to justify a larger sea level rise this century.
7. JEVREJEVA 2010: 60 to 180 cm: Jevrejeva, Svetlana, J. C. Moore, and Aslak Grinsted. “How will sea level respond to changes in natural and anthropogenic forcings by 2100?.” Geophysical research letters 37.7 (2010). Using an inverse statistical model we examine potential response in sea level to the changes in natural and anthropogenic forcings by 2100. With six IPCC radiative forcing scenarios we estimate sea level rise of 0.6–1.6 m, with confidence limits of 0.59 m and 1.8 m. Projected impacts of solar and volcanic radiative forcings account only for, at maximum, 5% of total sea level rise, with anthropogenic greenhouse gasses being the dominant forcing. As alternatives to the IPCC projections, even the most intense century of volcanic forcing from the past 1000 years would result in 10–15 cm potential reduction of sea level rise. Stratospheric injections of SO₂ equivalent to a Pinatubo eruption every 4 years would effectively just delay sea level rise by 12–20 years. A 21st century with the lowest level of solar irradiance over the last 9300 years results in negligible difference to sea level rise.
8. RAPER 2006: Contribution of mountain glaciers is 46-51 cm not 92-102 cm. Raper, Sarah CB, and Roger J. Braithwaite. “Low sea level rise projections from mountain glaciers and icecaps under global warming. Nature 439.7074 (2006): 311-313. The mean sea level has been projected to rise in the 21st century as a result of global warming¹. Such projections of sea level change depend on estimated future greenhouse emissions and on differing models, but model-average results from a mid-range scenario (A1B) suggests a 0.387-m rise by 2100 (refs 1, 2). The largest contributions to sea level rise are estimated to come from thermal expansion (0.288 m) and the melting of mountain glaciers and icecaps (0.106 m), with smaller inputs from Greenland (0.024 m) and Antarctica (- 0.074 m)¹. Here we apply a melt model³ and a geometric volume model⁴ to our lower estimate of ice volume^5,6,7 and assess the contribution of glaciers to sea level rise, excluding those in Greenland and Antarctica. We provide the first separate assessment of melt contributions from mountain glaciers and icecaps, as well as an improved treatment of volume shrinkage. We find that icecaps melt more slowly than mountain glaciers, whose area declines rapidly in the 21st century, making glaciers a limiting source for ice melt. Using two climate models, we project sea level rise due to melting of mountain glaciers and icecaps to be 0.046 and 0.051 m by 2100, about half that of previous projections^1,8.

SUMMARY AND CONCLUSION: The high level of uncertainty in the sea level rise projection from 40cm to 200cm implies that we do not have the data we need to make this forecast. This uncertainty problem is overcome in climate science with a perverse interpretation of uncertainty in terms of only that end of the uncertainty band that creates the greatest fear of fossil fuel emissions so that it can serve as motivation for climate action. This interpretation of uncertainty in climate science is described in a related post LINK: https://tambonthongchai.com/2020/04/22/climate-science-uncertainty/ .

Briefly, a large confidence interval does not mean “oh look how high it COULD be”. It means we do not have the data and/or information we need to make this projection; and that therefore we don’t really know. The less we know the higher it COULD be and with no information it COULD be as high as infinity because the answer is not constrained by information.