THIS POST IS A CRITICAL REVIEW OF A NEW CLIMATE SCIENCE ALARM IN SEPTEMBER 2020 ABOUT POLAR ICE MELT AND SEA LEVEL RISE
PART-1: THE RESEARCH PAPER AND MEDIA REPORT
RESEARCH PAPER: AUGUST 2020: Slater, T., Hogg, A.E. & Mottram, R. Ice-sheet losses track high-end sea-level rise projections. Nat. Clim. Chang. (2020). https://doi.org/10.1038/s41558-020-0893-y ABSTRACT: Observed ice-sheet losses track the upper range of the IPCC Fifth Assessment Report sea-level predictions, recently driven by ice dynamics in Antarctica and surface melting in Greenland. Ice-sheet models must account for short-term variability in the atmosphere, oceans and climate to accurately predict sea-level rise.
MEDIA REPORT IN SEPTEMBER 2020 https://www.sciencealert.com/ice-sheet-melting-is-perfectly-in-line-with-our-worst-case-scenario-scientists-warn
CLAIMS MADE AND CRITICAL COMMENTARY
CLAIM#1: The Greenland and Antarctic ice sheets, which hold enough frozen water to lift oceans 65 metres, are tracking the UN’s worst-case scenarios for sea level rise highlighting flaws in current climate change models. RESPONSE: The oft cited scary figure of 65 meters is fictional and meaningless. It has no interpretation in terms of AGW because no AGW projection exists for that scale of melt in polar ice. It should be mentioned that the complete disintegration of the West Antarctic Ice sheet in the previous interglacial, the Eemian, is the most dramatic polar ice melt event of the Pleistocene and that a caused sea level rise of about 7 meters with an uncertainty range of 5 to 9 meters. The Eemian interglacial is described in a related post on this site https://tambonthongchai.com/2018/12/21/eemian/ . This event occurred early in the Eemian under conditions that do not correspond to current Holocene climate but it has been used repeatedly since the Hansen 1988 testimony to raise fears of its recurrence 10,000 years into the Holocene as described in a related post on this site https://tambonthongchai.com/2019/07/16/antarctica-slr/ . There appears to be a desperate need in climate science to find ways to scare people with polar ice sheet melt and sea level rise that is a creation of fossil fuels and that can and must be avoided by giving up fossil fuels.
CLAIM#2: Mass loss from 2007 to 2017 due to melt-water and crumbling ice aligned almost perfectly with the IPCC most extreme forecasts, which see the two ice sheets adding up to 40 centimetres to global oceans by 2100, they reported in Nature Climate Change. Such an increase would have a devastating impact worldwide, increasing the destructive power of storm surges and exposing coastal regions home to hundreds of millions of people to repeated and severe flooding. RESPONSE: The period 2007-2017 that happens to match the rate of ice loss in a long term IPCC forecast is only a decade. The period is too short to infer long term impacts of anthropogenic global warming. As described in a related post, it is not possible to identify the effects of anthropogenic global warming at a decadal time scale because internal climate variability dominates at short time scales of 30 years or less. LINK: https://tambonthongchai.com/2020/07/16/the-internal-variability-issue/
3. CLAIM#3: The projected sea level rise is nearly three times more than mid-range projections from the IPCC’s last major Assessment Report in 2014, which predicts a 70-centimetre rise in sea level from all sources, including mountain glaciers and the expansion of ocean water as it warms. Despite this clear mismatch between the observed reality of accelerating ice sheet disintegration and the models tracking those trends, a special IPCC report last year on the planet’s frozen regions maintained the same end-of-century projections for Greenland, and allowed for only a small increase from Antarctica under the highest greenhouse gas emissions scenario. We need to come up with a new worst-case scenario for the ice sheets because they are already melting at a rate in line with our current one. Sea level projections are critical in helping governments plan climate policy, mitigation and adaptation strategies. If we underestimate future sea level rise, then these measures may be inadequate and leave coastal communities vulnerable. RESPONSE: The extreme level of uncertainty in future sea level rise projections means that climate science and the IPCC don’t have the information needed to make this forecast. That this forecast can and should be changed to maintain the needed urgency for climate action is a form of activism and not objective scientific inquiry. Besides, that such long term forecasts can and should be changed based on a decade of data that show a high rate of sea level rise violates fundamental statistical principles. It should also be noted that ice dynamics in the Arctic and in Antarctica cannot be understood purely in terms of fossil fuel emissions and anthropogenic global warming because these are geologically active regions where where internal heat sources of the earth play a significant role as described in two related posts on this site: ARCTIC LINK: https://tambonthongchai.com/2019/07/01/arctic/ ANTARCTICA LINK: https://tambonthongchai.com/2019/06/27/antarctica/
CLAIM#4: Ice sheet losses at the upper end of the IPCC forecasts would by itself expose some 50 million people to annual coastal flooding worldwide by mid-century, according to research published last year. Total sea level rise of at least a metre would likely require spending upward of $70 billion a year in sea walls and other defenses against flooding. Several factors explain why the climate models underlying UN projections for sea level might have given short shrift to ice sheets, according to the new analysis. Ice sheet models do well in describing the long-term impact of gradual global warming, which has seen temperatures at the poles rise far more quickly than for the planet as a whole. But they have failed to account for short-term fluctuations in weather patterns that are, themselves, deeply influenced by climate change. For Greenland, much of the ice loss is now being driven by surface melt events during hot summers – processes not captured in the AR5 simulations,“ said Slater, referring to the 2014 IPCC report, the fifth since 1992. „We needs to understand these better to improve our sea level rise predictions.“ RESPONSE: That ice sheet losses at the upper end of the IPCC forecasts is invoked is an example of the misinterpretation of uncertainty in climate science described in a related post on unceertainty https://tambonthongchai.com/2020/04/22/climate-science-uncertainty/ . There we note that „UNCERTAINTY DOES NOT MEAN OH! LOOK HOW HIGH IT COULD BE. IT MEANS WE DON’T REALLY KNOW. THE LESS WE KNOW THE HIGHER IT COULD BE AND IN PERFECT IGNORANCE IT COULD BE AS HIGH AS INFINITY BECAUSE THE ANSWER IS NOT CONSTRAINED BY INFORMATION„. It is a gross misinterpretation to present uncertain data as certainty of the high end in terms of some kind of precautionary principle. The large uncertainty in sea level rise projections means climate science is unable to make such projections based purely on fossil fuel emissions and atmospheric phenomena. The implication of this uncertainty is not certainty of high values but perhaps that important geological variables have been missed in an analysis driven by the atmosphere bias of climate science. The interpretation of convenience when faced with uncertainty is a form of the confirmation bias fallacy described in a related post LINK https://tambonthongchai.com/2018/08/03/confirmationbias/
CLAIM#5: Until the turn of the 21st century, the West Antarctic and Greenland ice sheets generally accumulated as much mass as they shed. Runoff, in other words, was compensated by fresh snowfall. But over the last two decades, the gathering pace of global warming has upended this balance. RESPONSE: A hundred years of sea level stability from 1900 to the year 2000 is compared with a 20-year period when a net ice melt was observed where snowfall did not keep pace. This comparison is not possible for two reasons. First, the period of 20 years is relatively brief for this kind of analysis because of the extreme variation in decadal ice melt data and secondly, if there were 20-year periods in the reference century when there was not enough snowfall to overcome ice melt, then the comparison has no interpretation. It should also be noted that if the ice melt anomaly in the most recent 20 years is being interpreted in terms anthropogenic global warming, we should note that the study period is too short for such attribution as described in a related post LINK https://tambonthongchai.com/2020/07/16/the-internal-variability-issue/
CLAIM#6: Last year, Greenland lost a record 532 billion tonnes of ice – the equivalent of six Olympic pools of cold, fresh water flowing into the Atlantic every second. This run-off accounted for 40 percent of sea level rise in 2019. RESPONSE: In the context of this article, the 532 gigatons of ice melt is best understood in terms of a sea level rise about 1.5mm and not in terms of Olympic swimming pools. Also a one year event does not have an interpretation of sea level rise that can be related to anthropogenic global warming particularly so in this article as the polar regions under study exhibit episodic ice melts events that are purely geological in nature and without an atmospheric interpretation.
CLAIM#7: Earth’s ice masses – including mountain glaciers, the Arctic ice cap, and both ice sheets – lost nearly 28 trillion tonnes of mass between 1994 and 2017. Less than half of that amount contributed to sea level rise. The Arctic ice cap, for example, forms in the ocean, and thus does not increase sea level when it melts. The rate of ice loss, they found, has increased nearly 60 percent of that time period. RESPONSE: Over this 23-year period the sea level rose at an average rate of 1.66mm/year rising from 1.3mm/year at the beginning to 2mm/year at the end. This rapid change in a brief time span has no AGW climate change implication and must therefore be understood in terms of the extensive geological features of the Arctic and of Antarctica that can explain sudden and violent events of this nature. The time span of 23 years restricts an AGW climate change interpretation because of the internal climate variability issue LINK https://tambonthongchai.com/2020/07/16/the-internal-variability-issue/