Key Atlantic Meridional Overturning Circulation (AMOC) Likely To Collapse In 2025-2095

Atlantic Meridional Overturning Circulation AMOC
Map of the thermohaline circulation, also known as the global meridional overturning circulation (GMOC) of which the Atlantic overturning circulation is a part of. Map: NASA.

The Atlantic Meridional Overturning Circulation (AMOC) moves warm water from the Indian Ocean, the Southern Ocean and the South Atlantic into the North Atlantic where it cools, sinks and flows south. However global warming and Greenland ice melting has the tendency to suppress this system. Potential AMOC collapse has worried climate scientists and now the latest research published in Nature Communications predicts a devastating collapse of the AMOC in the period 2025-2095.

In a recent very detailed paper in Nature Communications  Peter Ditlevsen (professor in physics of ice, climate and earth, University of Copenhagen) and Susanne Ditlevsen (statistician and professor, Department of Mathematical Sciences, University of Copenhagen) have reported the likelihood of such collapse this century: “The Atlantic meridional overturning circulation (AMOC) is a major tipping element in the climate system and a future collapse would have severe impacts on the climate in the North Atlantic region. In recent years weakening in circulation has been reported, but assessments by the Intergovernmental Panel on Climate Change (IPCC), based on the Climate Model Intercomparison Project (CMIP) model simulations suggest that a full collapse is unlikely within the 21st century. Tipping to an undesired state in the climate is, however, a growing concern with increasing greenhouse gas concentrations. Predictions based on observations rely on detecting early-warning signals, primarily an increase in variance (loss of resilience) and increased autocorrelation (critical slowing down), which have recently been reported for the AMOC. Here we provide statistical significance and data-driven estimators for the time of tipping. We estimate a collapse of the AMOC to occur around mid-century under the current scenario of future emissions… In this work, we show that a transition of the AMOC is most likely to occur around 2025-2095  (95% confidence interval)” [1].

Damian Carrington (environment editor, The Guardian) has reported on this finding: “The Gulf Stream system could collapse as soon as 2025, a new study suggests. The shutting down of the vital ocean currents, called the Atlantic Meridional Overturning Circulation (Amoc) by scientists, would bring catastrophic climate impacts… Amoc carries warm ocean water northwards towards the pole where it cools and sinks, driving the Atlantic’s currents. But an influx of fresh water from the accelerating melting of Greenland’s ice cap and other sources is increasingly smothering the currents. A collapse of Amoc would have disastrous consequences around the world, severely disrupting the rains that billions of people depend on for food in India, South America and west Africa. It would increase storms and drop temperatures in Europe, and lead to a rising sea level on the eastern coast of North America. It would also further endanger the Amazon rainforest and Antarctic ice sheets” [2].

The IPCC has assessed that “The AMOC is projected to weaken in the 21st century under all RCPs [Representative Concentration Pathways] (very likely), although a collapse is very unlikely (medium confidence)” [3, 4]. However eminent climate scientist Professor  Stefan Rahmstorf (Professor of Physics of the Oceans at Potsdam University, Germany, and writing before the Ditlevsens’ paper was published) has commented (2023): “It has long been my opinion that “very unlikely”, meaning less than 10% in the calibrated IPCC uncertainty jargon, is not at all reassuring for a risk we really should rule out with 99.9 % probability, given the devastating consequences should a collapse occur… Timing of the critical AMOC transition is still highly uncertain, but increasingly the evidence points to the risk being far greater than 10 % during this century – even rather worrying for the next few decades. The conservative IPCC estimate, based on climate models which are too stable and don’t get the full freshwater forcing, is in my view outdated now” [4].

Professor Rahmstorf and colleagues (2019) listed the following 9 key tipping points in the worsening climate crisis [5]:

(1) West Antarctica (Amundsen Sea embayment) (the tipping point may have been exceeded and this could destabilize the rest of the West Antarctic ice sheet leading to circa 3 metres of sea-level rise on a timescale of 100s to 1000s of years, noting that this has happened in the past);

(2). East Antarctic ice sheet (Wilkes Basin) (approaching a tipping point with 3-4 metres in sea level rise on a time scale of 100s of years);

(3). Greenland ice sheet (melting at an increasing  rate and the tipping point may be the circa +1.5C expected in about 2030, with 7 metres sea level rise over 1000s of years);

(4) Arctic sea ice (massive sea ice loss already and at +2C there is a 10–35% probability of near-total summer sea ice loss);

(5). Coral reefs (mass coral bleaching worldwide and loss of 50% of the coral of  Australia’s iconic Great Barrier Reef due to warming, ocean acidification, pollution and Crown of Thorn predator  population explosion, with 99% of tropical corals predicted to be  lost at +2C and massive attendant loss of  marine biodiversity and fisheries);

(6) Amazon rain  rainforest (estimated tipping point at 20% – 40% deforestation with about 17% lost since 1970, and this world’s largest rainforest containing 1 in 10 known species, having a continent-scale  climate impact, and presently burning on a huge scale);

(7). North American boreal forest (warming in the sub-Arctic has led to insect pest population explosion, boreal (high latitude) tree die-off and fires, with some boreal forest regions converting from being carbon sinks to a carbon sources);

(8) Arctic permafrost (irreversible thawing and release of carbon dioxide (CO2) and methane (CH4) with Arctic warming about 2 times bigger than the global average, and noting that  CH4 has an estimated Global Warming Potential (GWP) as low as 21 relative to the same mass of CO2 on a 100 year time-scale, but on a 20 year time scale and with aerosol impacts included it is 105); and

(9) Atlantic Meridional Overturning Circulation (AMOC) (the  key salt- and heat-conveying Atlantic Ocean circulation system subject to a 15% slow-down since the mid-20th century with Arctic sea-ice loss increasing  regional warming,  Arctic warming and Greenland melting putting  fresh water into the North Atlantic, and slowdown in the AMOC destabilizing the West African monsoon, impacting drought in the Sahel region, drying the Amazon, disrupting the East Asian monsoon and warming the  Southern Ocean with increased  Antarctic ice loss; see [6, 7]).

Now the Ditlevsens’ paper provides strong evidence for  a disastrous collapse of  the Atlantic Meridional Overturning Circulation (AMOC) in 2025-2095 [1].

Humanity and the Biosphere are existentially threatened by nuclear weapons and climate change. Eminent physicist Professor  Stephen Hawking has stated the problems and solutions very succinctly: “We see great peril if governments and societies do not take action now to render nuclear weapons obsolete and to prevent further climate change” [8, 9]. A paper co-signed by over 11,000 scientists  has detailed trends in 24 climate-related  areas over the last 40 years.  Scientists became aware of the climate change threat from greenhouse gas (GHG) pollution in the 1980s, but in 21 of these 24 areas the trends are (a) huge, (b) in the wrong direction, and (c) linear or quasi-linear functions of time, with this allowing extrapolation from the present climate emergency to a climate catastrophe in 2030 [10-13].

Of course if the “we are tackling climate change” assertion  of politicians has any substance it must involve decreases in key parameters associated with greenhouse gas (GHG) pollution. However from a global perspective this is simply is not happening. There is no decrease in our presently peak global production of coal and methanogenic cattle. The atmospheric carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) are remorselessly increasing, as are oil and  gas use.  Greenhouse gas (GHG) producing cement, steel, and iron ore production are all increasing. Humanity should be radically decreasing these terracidal activities but, political rhetoric aside, is damning the planet through  catastrophic global inaction. The biodiversity loss is increasing catastrophically with a species extinction rate (speciescide rate) that is 100-10,000 times greater than the background extinction rate. While the rate of deforestation has decreased 3-fold since 1980, and net re-afforestation of temperate forests is now occurring, the deforestation rate in tropical forests levelled out to an appalling 50 million hectares per decade over the last 2 decades. Unless something radical happens we are doomed, the planet is doomed, and Humanity and the Biosphere face decimation [14].

Faced with an ever-worsening climate crisis what must Humanity do? We must (a) inform everyone we can, and (b) apply Boycotts, Divestment and Sanctions (BDS) to all people, politicians, parties, collectives, corporations and countries disproportionately involved in deadly and terracidal climate criminality.

References.

[1]. Peter Ditlevsen and Susanne Ditlevsen, “Warning of a forthcoming collapse of the Atlantic meridional overturning circulation”, Nature Communications, 14, Article number: 4254, 25 July 2023: https://www.nature.com/articles/s41467-023-39810-w .

[2]. Damian Carrington, “Gulf Stream could collapse as early as 2025, study suggests”, The Guardian, 26 July 2023: https://www.theguardian.com/environment/2023/jul/25/gulf-stream-could-collapse-as-early-as-2025-study-suggests .

[3]. IPCC, “Special Report on the Ocean and Cryosphere in a Changing Climate”: https://www.ipcc.ch/srocc/ .

[4]. Stefan Rahmstorf, “What is happening in the Atlantic Ocean to the AMOC?”, Real Climate, 24 July 2023: https://www.realclimate.org/index.php/archives/2023/07/what-is-happening-in-the-atlantic-ocean-to-the-amoc/ .

[5]. Timothy Lenton, Johan Rockstrom, Owen Gaffney, Stefan Rahmsorf, Katherine Richardson, Will Steffen and Hans Joachim Schellnhuber,  “Climate tipping points – too risky to bet against” , Nature 575, 592-595, 27 November 2019: https://www.nature.com/articles/d41586-019-03595-0 .

[6]. Gideon Polya, “Climate Scientists: Planetary Emergency, Planet In Peril, Act Now”, Countercurrents, 3 December 2019: https://countercurrents.org/2019/12/climate-scientists-planetary-emergency-planet-in-peril-act-now/ .

[7]. Gideon Polya, “Climate Crisis, Climate Genocide & Solutions”, Korsgaard Publishing, 2020.

[8]. Professor Stephen Hawking quoted in  Will Dunham, “Nuclear, climate perils push Doomsday Clock ahead”, Reuters, 22 January 2007: https://www.reuters.com/article/idUSN17314370 .

[9].  Stephen Hawking, “Brief Answers to the Big Questions”, John Murray, 2018, Chapter 7.

[10 ]. William Ripple et al.., “World scientists’ warning of a climate emergency”, BioScience,  5 November 2019: https://academic.oup.com/bioscience/advance-article/doi/10.1093/biosci/biz088/5610806 .

[11]. Gideon Polya, “Extrapolating 11,000 scientists’ climate emergency warning to 2030 climate catastrophe”, Countercurrents, 14 November 2019:  https://countercurrents.org/2019/11/extrapolating-11000-scientists-climate-emergency-warning-to-2030-catastrophe .)

[12]. William J. Ripple et al., 15,364 signatories from 184 countries, “World scientists’ warning to Humanity: a second notice”, Bioscience, 13 November 2017: https://academic.oup.com/bioscience/advance-article/doi/10.1093/biosci/bix125/4605229 .

[13]. Gideon Polya, “Over 15,000 scientists issue dire warning to humanity on catastrophic climate change and biodiversity loss”, Countercurrents, 20 November 2017: https://countercurrents.org/2017/11/20/over-15000-scientists-issue-dire-warning-to-humanity-on-catastrophic-climate-change-and-biodiversity-loss/ .

[14].Gideon Polya, “Planet Doomed: No Decrease In Record GHGs & Gas, Oil, Coal, Cattle, Cement & Steel Production”, Countercurrents, 16 October 2022: https://countercurrents.org/2022/10/planet-doomed-no-decrease-in-record-ghgs-gas-oil-coal-cattle-cement-steel-production/ .

Dr Gideon Polya taught science students at La Trobe University, Melbourne, Australia over 4 decades. He published some 130 works in a 5 decade scientific career, notably a huge pharmacological reference text “Biochemical Targets of Plant Bioactive Compounds”. He has also published “Body Count. Global avoidable mortality since 1950” (2007, 2022) and “Jane Austen and the Black Hole of British History” (1998, 2008, 2023). He has recently published “US-imposed Post-9-11 Muslim Holocaust & Muslim Genocide” (2020), and “Climate Crisis, Climate Genocide & Solutions” (2020), and contributed to Soren Korsgaard (editor) “The Most Dangerous Book Ever Published – Dangerous Deception Exposed!” (2020). For images of Gideon Polya’s huge paintings for the Planet, Peace, Mother and Child see: http://sites.google.com/site/artforpeaceplanetmotherchild/  .

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