Still living on the coast in the 22nd century E-Book

Jean-Marc Beynet

• Herausgeber: Books on Demand
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 286

Veröffentlichungsjahr: 2024

Beschreibung

Since the industrial revolution and coal mining in the 19th century followed by oil and gas drilling in the 20th century, massive CO2 emissions are responsible for global warming and rising sea levels, which will continue until political and industrial energy decision-makers put in place effective energy transition solutions. In the meantime, younger generations are worried and some even suffer from climate eco-anxiety. This book gives examples of simulated coastal submersion, based on selected examples in the North Sea, the Mediterranean, the English Channel, the Atlantic, and on islands in the Caribbean, the Pacific and the Indian Oceans. Then, to reassure the generations of the 22nd century, this book explains the energy transition, the advantages of green hydrogen in particular, low-carbon architecture, carbon neutrality for large cities and biomimicry. Finally, it proposes solutions for the adaptation of existing coastal settlement, as well as for the construction of new types of housing on stilts and/or floating, for CO2 capture, the adaptation of port infrastructures, multi-purpose offshore platform designs, and floating cities. It is to help today's youth that this book was written, so that future generations don't need to be afraid of the sea; instead of running away, they can continue to live on the coast. Full of illustrations, it includes 73 colour pages presenting 40 maps, 62 photos and 26 graphs or 3D sketches.

Leseprobe

As part of an eco-responsible approach, this book is available in two versions, printed and digital (e-book). In the case of the printed version, to avoid wasting paper, the stock is deliberately reduced, and the book is printed on demand after ordering.

Books already published by the same author:

Habiter ou abandonner le littoral d’ici 2100 – Prospective et propositions pour l’Occitanie, published in 2020 by Nombre7 Editions (France).

Ces îles de Méditerranée qui n’en n’étaient pas il y a 20 000 ans - Prospective sur leur devenir pour la fin du siècle, published in 2020 by Nombre7 Editions (France).

La vie des îles autour du monde, naissance, histoire, présent, futur probable, published in 2021 by Nombre7 Editions (France).

Cités déjà englouties, littoraux bientôt submergés, published in 2022 by Nombre7 Editions (France).

Vingt mille kilomètres sous les mers (Preface by Jean Verne, great grandson of Jules Verne), published in 2023 by Nombre7 Editions (France).

De la Bourgogne à la Camargue, navigation sur la Saône et le Rhône, bilingual text French/English – published in 2023, BoD Editions.

To future generations who will experience the 22nd century

Table of contents

Preface

Foreword

Chapter 1: Past and future sea level fluctuations

Astronomical fluctuations: the Milanković cycles

Other sea level fluctuations (tides, seiches, tsunamis)

Astronomical tides

Barometric tides

Seiches

Tsunamis

Accelerated sea level rise due to industrial activities: IPCC projections for 2100-2300

Sixth synthesis IPCC Report (published on the 20

th

of March 2023)

Chapter 2: Examples of prospective simulations of coastal flooding in the 22nd century

North Sea and the English Channel

Coastline of Hauts-de-France, Belgium, the Netherlands, Germany and Denmark

The Channel Islands (Jersey, Guernsey, Sark)

Mediterranean Sea

The city of Alexandria in Egypt

Venice on the Adriatic Sea, Italy

The Camargue, France

Atlantic Ocean and Caribbean Sea

France: the island of Sein off the coast of Brittany

Madeira Archipelago (Portugal)

Archipelago of the Canary Islands (Spain)

North America: New York

Caribbean Sea, West Indian Arc: Barbados, Montserrat and Sint-Maarten

Pacific Ocean

Easter island, Rapa-Nui

French Polynesia

Samoa, Wallis-et-Futuna, Tonga, Tuvalu, Kiribati, Fiji, Solomon Islands, Vanuatu

Nan Madol

Indian Ocean

Maldives Archipelago

Seychelles

Mauritius

Persian Gulf

Dubai and its artificial islands

Sea level rise in the Persian Gulf around 2100

Chapter 3: Climate eco-anxiety: facts and solutions

The findings: Youth and climate anxiety

COP Climate: COP 21 (Paris) and recent COPs (Glasgow in 2021, Sharm-El-Sheikh in 2022 and Dubaï in 2023)

Solutions for moving forward: moving to individual or collective action

Take ownership of the problem and take action, each at their own level

Publicising the risks of climate change and sea level rise

Civil disobedience by scientists

Many young graduates want to work in the ecoindustry or the environment

Accelerating the implementation of the energy transition

In France, the law on the energy transition for green growth (LTECV)

The specific case of hydrogen

Abandonment of sales of combustion engine vehicles by 2035

Encouraging research on biomimicry

Digitise in the metaverse that which cannot be protected against flooding and is destined to be swallowed up

Chapter 4: Technical solutions for adapting coastlines for the 22nd century

Implementing a low-carbon architecture

Where possible, adapt existing habitats

For new housing, encourage the design of houses on stilts and floating houses

Adapting port and airport infrastructures

Implementing POMUs/MUOPs (Multi-Usage Offshore Platforms ) and floating cities

Sharing POMU/MUOP discoveries to educate the younger generation

POMU/MUOP for CO2 capture

Summary of the Occitan'île and Capt-CO2 POMUs

Taking care of rivers and other inland waterways

Chapter 5: Conclusions, recommendations

Bibliography

Credit for maps and other illustrations

Acknowledgments

The author

Preface

This latest book is the work of an engineer specialising in subjects dealing with the coastline in the face of climate change, Jean-Marc Beynet. This book, of which I was the first to receive a copy, is the latest in a series of five successive works written by him since 2019/2020, all of which are major works in this field.

This series is a real inventory of the situation at different scales of space and time. It focused on and dealt mainly with the impacts and challenges of the fundamental issue of marine submersion, in the context of different hypotheses put forward on its progression up to the year 2100.

The author goes far beyond the numerous proposals that he pertinently sets out by showing that they are technically feasible. He expresses his vision in a skilful alchemy of culture and technique, to the great interest and pleasure of his readers.

In addition to the profile of scientific specialist that he is known for through his numerous contributions and expert studies, the present book allows him to shed more light on the resolutely humanist facet of his "earthly ambitions".

Through the exploration of (these) many exciting perspectives, Jean-Marc Beynet proposes a real message of hope addressed to all generations, from the youngest to the oldest, all united to launch themselves into the 22nd century, in this new book.

He and I belong to this generation which, from now on and very urgently, must be concerned about the stress and pessimism, or even the ambient scepticism, which has been gradually instilled in the minds of those who, primarily among our confined youth, have observed so much degradation in our biosphere, due in part to certain excesses of the technosphere.

This latest book, well documented technically, is like the previous editions. However, this one goes much further. It shows the way to the many actors of an emerging change of mindset, more participative and collective, which deeply animates the human society. This mindset should quickly be adopted in front of all audiences and especially young people who have doubts.

We cannot build a future we want to believe in if we do not know how to build a present together.

It is a question of encouraging them to put themselves "in a state of research and project", as Jean-Marc Beynet knows how to do so well. The numerous architectural and engineering projects presented are very evocative of a creative and dynamic form of experimental research and development, with a wealth of feasible works, to bring about the hoped-for re-enchantment: to restore confidence in our knowledge-based society, in the ability to master constraints and to know how to seize them as opportunities to build a desirable common future.

In this sense, the author's writing is commendable and pleasing. His message of hope is in an ethical vein that is both dynamic and forward-looking, and strongly rooted in the present of our scientific knowledge. This is reminiscent of the 'principles of hope' in a future found in Edgar Morin's Réveillons-nous! Let's wake up, published in March 2022, where the ambition, albeit more distant, is to 'civilise the Earth' in order to open up those same 'grandiose perspectives capable of mobilising energies'.

In a quote from Andrew Kötting's film IVUL, the figure of "the tree appears to be characteristic of a civilisation that develops when the elders plant trees knowing that they will never rest under their shade".

This is what ultimately characterises the series of works by our 'engineer-architect'. Rooted in our knowledge-based societies, the "tree" planted by the author with the aim of "opening perspectives" towards a desired future should not fail to mobilise intergenerational energies, in a collective intelligence for a responsible life, immediately taken up by the youngest and accompanied at least for a while by the elders, some of whom we know will not live through the 22nd century.

A hymn to inventiveness and to man's capacity for adaptation and resilience.

There is a growing number of individuals who are passionate about observing nature and have a deep appreciation for all living things, regardless of whether they prefer low-tech or high-tech methods. This gives us hope that a new type of economy, known as a trans-modern economy, can emerge. This economy will focus on regenerating living things and strengthening social connections.

A biomimetic researcher and lecturerin engineering at the University of California, co-author of an article published in Nature Sustanibility, states that "nature is the quintessence of inventiveness and engineering".

What if Man's capacity for adaptation and resilience - as a keen observer of nature and living things - gave us reason to hope in the face of what is already being called the Anthropocene? By observing nature as our mentor, we have gained a wealth of technological knowledge that can be used to guide us towards a more ethical, just, and human 22nd century. Inspired by the example set by Jean-Marc Beynet's explanations, we can strive to create a better future for all.

Together, as this book shows, we can build a meaningful society. Clearly, Jean-Marc Beynet was keen to point out: "We know how to do it"!

Jean-Louis PACITTO

Honorary architect, prospective urban planner

Member of CEEBIOS, European Centre for Studies and Expertise in Biomimicry, Senlis (France)

Foreword

Over the past 20,000 years, the average level of the world's seas has risen by 120 metres. This was mainly due to astronomical reasons and led to the end of the last ice age. This was not a problem for prehistoric hunter-gatherer populations, who were nomadic and could retreat away from the coastline as sea levels rose. In the Neolithic period, men began to settle down and build megaliths. Then, in ancient times, port cities were built on the coasts in order to develop trade between peoples. And many cities are now sunken as the sea continues to rise.

However, in recent decades, the rise in sea level has accelerated significantly due to the runaway human activities of the Industrial Revolution, which release CO2 and methane into the atmosphere. Part of our coastal heritage will be partially (and sometimes even totally) submerged, both for continental coasts and for certain islands around the globe.

And yet, in most countries in the world, many people are concentrated on the coastlines to live near the seas and oceans. Why do coastal areas attract so many people? This is understandable for those who make their living from the sea, such as fishermen, or in this day and age, for those who work in sea-related tourism and water-based leisure activities. But why do so many other people gather so close to the sea, even though they do not earn their income from it? The coastline that attracts so many people is not always kind to its residents. In some areas, there are deadly tsunamis, destructive cyclones, floods and marine submersions that are also dangerous for the population.

The aim of this text is to provide solutions to future generations so that the coastline remains desirable and habitable in the decades to come. This book is also a cry of alarm addressed to political decision-makers, elected representatives, energy industrialists and consumers, to help raise their awareness of the urgent need to stop the exploitation and use of fossil fuels, which release CO2 into the atmosphere and are largely responsible for climate change and rising sea levels.

In this book, Chapter 1 first presents the past fluctuations of sea level, caused by the Milanković cycles, which explain the alternations of glacial and interglacial periods. Then, it analyses the industrial revolution’s impact – from the invention of the steam engine in England by James Watt in 1769, the industrial revolution and coal mining in the 19th century, up until followed by oil and gas drilling in the 20th century. The massive CO2 emissions produced during this period are responsible for global warming and rising sea levels and will continue until political and industrial energy decision-makers put in place effective energy transition solutions. However, these policies are slow in coming to fruition because the first victims of global warming are generally not those who cause it. The industrialised countries, which are rich in principle, will have to help the poor countries because the latter are not responsible and do not have sufficient financial resources to adapt to the rise in sea levels on their coasts in the coming decades. The latest IPCC1 reports are presented in this chapter 1, in particular the recent AR6 (2021-2022).

Chapter 2 shows simulations of coastal flooding, using selected examples from the North Sea, Mediterranean, and Atlantic as well as islands in the Caribbean, Pacific and Indian Oceans.

While policy makers are slow to reach agreements between rich and poor countries, younger generations are worried and impatient that their elders are failing to address the climate emergency. Indeed, the Conferences of the Parties (COPs2), which have been held annually for almost thirty years, have struggled to come to agreements to stop using fossil fuels and for rich countries to provide funding for poor countries. Currently, about half of the 15-30 year old age group is said to suffer from climate eco-anxiety and fear for their future, while industrialists and political decision-makers are dragging their feet regarding this problem, which should be a priority due to its link with the future of planet Earth and living beings (humans and wildlife). Some even go so far as to fear a new mass extinction! These fears are explained in Chapter 3, which also presents actions already taken by young people who have taken steps to combat global warming.

After giving possible solutions to accelerate the energy transition, Chapter 4 is very pragmatic and proposes solutions for adapting the coastline so that it remains attractive and habitable for the populations that will replace us in the 22nd century.

Finally, Chapter 5 concludes with a summary of actions and recommendations for the future.

It is to reassure today's youth that this book was written. So that future generations will not be afraid of the sea, will not need to flee from it, and on the contrary, will be able to continue to live on the coast. Of course, in some of the most critical cases, it will still be necessary to consider local policies of strategic withdrawal and spatial recomposition. Sometimes, it will even be necessary to decide to abandon the land and let the sea take over. We already know that this will be the case for small islands, which lie very low in the water, such as the Tuvalu archipelago for example. However, on other less vulnerable coastlines, it will be possible to continue to live there, provided that they adapt. For those who choose to stay, the design of floating buildings in some cases, or on stilts in other cases, could be envisaged, provided that hydrodynamic phenomena such as storms and sometimes cyclones with temporary barometric surges in tropical areas are taken into account.

Finally, in other cases, it will be tempting to advance on the sea, by implanting artificial islands offshore, in sheltered areas.

1 The Intergovernmental Panel on Climate Change (IPCC) is the United Nations body for assessing the science related to climate change. Created in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), the objective of the IPCC is to provide governments at all levels with scientific information that they can use to develop climate policies. IPCC reports are also a key source of input for international climate change negotiations.

2 The Conference of the Parties (COP) was established when the United Nations Framework Convention on Climate Change (UNFCCC) was adopted at the Earth Summit in Rio de Janeiro in 1992. It is the supreme body of the Convention and has met annually since 1995. It brings together representatives of the states that have signed the UNFCCC, as well as civil society actors such as non-governmental organisations (NGOs), local and regional authorities, trade unions, businesses, etc. The aim of the COP is to develop the UNFCCC by taking stock of the application of the commitments made in favour of the Climate, by clarifying them, and by negotiating new commitments.

Chapter 1: Past and future sea level fluctuations

Astronomical fluctuations: the Milanković cycles

The sea level has changed significantly over geological time, on three different time scales (Ifremer, 2012).

Since the Primary Era, i.e. for the last 350 million years, sea level has varied greatly, with amplitudes of up to 380 metres, with high sea levels known to be more than 250 metres above present sea level;

At the end of the Tertiary era and during the Quaternary, sea level varied with an amplitude of between 30 and 130 metres and a cyclicity of the order of 40,000 years, gradually increasing to 100,000 years between 1.2 million and 800,000 years ago (Middle Pleistocene Revolution);

Since the last glacial maximum, which is equivalent to the last 20,000 years, the sea level has risen from -130 metres to the level we know in our contemporary period.

The causes of sea level change differ from one era to another. Indeed, while the evolution of continental masses and ocean basins (linked to plate tectonics) explains most of the variations in sea level over the last 350 million years (variations in the container), it is variations in climate and the volume of continental ice (i.e. glaciers and ice caps) that have controlled the evolution of sea level (variation in the content) over the last few million years (particularly since the beginning of the Quaternary period, 2.6 million years ago). The thermal expansion of the oceans (due to the average rise in atmospheric temperatures) and the melting of glaciers and ice caps at high latitudes explain the current rise in sea level (a few millimetres per year).

In addition, apart from these cyclical variations in sea level on an Earth-wide scale, there has been a particular and specific geological phenomenon, but only in the Mediterranean: the "Messinian salinity crisis3".

Secondly, at the global level, the "Milanković cycles" explain the alternations between glacial and interglacial periods.

In 1941, Milutin Milanković, a Serbian mathematician and astronomer explained the alternation of glacial and interglacial cycles during the Quaternary (Milankovitć, 1941 and 1944; Ivanović, 2012). Glaciation occurs when the high latitudes of the northern hemisphere receive reduced solar radiation during the summer. The three astronomical parameters that combine to influence the climate on Earth are:

1. The eccentricity of the Earth's orbit: The Earth's orbit is an ellipse, with the Sun as one of the foci. The eccentricity of the ellipse is the distance between the two foci. When the eccentricity is small, the Earth's orbit is almost circular. The eccentricity varies according to the gravitational attractions between the Earth and the other planets. The characteristic period of variation of this parameter is 100 000 years.

2. The obliquity of the Earth's axis of rotation with respect to the plane of the ecliptic4: The angle formed by the direction of the poles and that of the normal to the plane of the ecliptic is not constant. It varies between 22° and 24.5° over a period of 41,000 years. Thus, depending on the obliquity, the poles do not receive the same level of solar radiation.

3. The precession of the equinoxes: The Earth turns on itself like a top. Its axis of rotation sweeps along a cone, which varies over a period of 20,000 years. The tilt of the Earth's rotational axis does not affect the total amount of solar heat received by the Earth, but its distribution.

It was more than a century before Milutin Milanković that Swiss, German, French and Scottish scientists had put forward hypotheses about past glaciations. For example, in Switzerland, in as early as 1820, Karl Kasthofer and Ignatius Venetz were interested in climate change in the Alps. They pointed out "erratic blocks", which are huge rocks of different composition from the surrounding terrain and which bear marks of displacement on their surface. Such boulders have been identified in the Alps, as well as in Germany and Scandinavia. In 1829, Venetz hypothesised that these blocks were carried by glaciers which left them behind when they receded. In 1835, the German-Swiss geologist Jean de Charpentier published an article in which he described "a monster glacier" that covered the upper Rhône valley in the distant past. Then another Swiss, Louis Agassiz, clarified this hypothesis in 1837 by presenting the theory of ice ages. According to him, a whole part of Europe would have been covered by a crust of ice that would have melted over the course of the Earth's history. This theory was gradually accepted by the scientific community between 1840 and 1860. But how could the reasons for this be explained? The French mathematician Joseph-Alphonse Adhémar was the first to suggest an astronomical reason in his book entitled Révolutions de la mer, déluges périodiques (Revolutions of the Sea, Periodic Floods), published in 1842. He suggested that the large ice crust described by Agassiz could be an extension of the North Pole ice pack, whose disappearance could be explained by the precession of the equinoxes, the slow change of direction of the Earth's axis.

Later, in 1864, the Scotsman James Croll was inspired by Adhemar to present an even more ambitious theory, taking into account not only the precession but also the evolution of the Earth's orbit, the weight5 of the ice mantles, ocean currents, and the circulation of the atmosphere to explain the alternation of glacial phases and warmer sequences (Fressoz et al., 2010; 2020).

Let us now return to Milanković's6 astronomical theory, which helps to explain the great climatic variations of the glacial cycles7. Thus, as the climate has gradually warmed since the last ice age, the sea level has risen by 120 metres from the peak of the last ice age about 20,000 years ago, with the following approximate intermediate levels:

These values remain approximate because the rise in sea level has not been linear over time. There have been variations at different times. The most rapid rise occurred in the period 18,000 - 5,000 BC. For example, in the Mediterranean, all the stations indicate a constant slowing down of the overall rate of relative rise of the water level over the last 4500 years. The Holocene marine transgression seems to have ended in Provence around 500 years AD (Morhange, 1994). Between 4000 and 500 BC, the maximum rate of relative sea level rise is about 0.03 cm/year. Between 500 BC and 250 AD, the relative sea level rise was much faster (0.13 cm/year). As we will see later, since the end of the 18th century, due to the CO2 released into the atmosphere by industrial activities, this rise in the world's seas is clearly accelerating, even if it is imperceptible to some.

Now let's look at megaliths built near the sea by Neolithic Man, particularly in Brittany. At that time, the sea level was about 8 m lower than it is now. For example, the covered alley of Guinirvit is located in the Bay of Kernic in Plouescat in Finistère (France). Located on the foreshore, it is one of the witnesses to the variations in sea level and the subsidence of the soil since the end of the last ice age.

"There are many covered alleys more or less well preserved in Brittany, a kind of dolmen preceded by a stone alley and sometimes surrounded by a crown of upright stones (peristalite). The one at Guinirvit is particularly ruined and, in particular, has lost its horizontal slabs used as a ceiling. Like all its counterparts, it dates from the early Bronze Age (2500 BC). Its originality lies in the fact that it is located entirely on the foreshore. Discovered at low tide, it is entirely submerged during high tides. As the Bronze Age builders certainly did not build this walkway in the tidal zone, this means that the sea has risen or that this area of Brittany has sunk by a few metres over the last 4,500 years." (Thomas, 2015).

Location of the Anse de Kernic west of Roscoff (© Navionics - Do not use for navigation)

The author Jean-Marc Beynet on the site of Guinirvit (France) at low tide at the beginning of September 2021 (© Annick Beynet, 2021)

On this coast of North Finistère (France) let us also point out other megaliths submerged at each high tide, which are also witnesses of the rise in sea level since the Neolithic period: the Men-0zac'h menhir at Plouguernau on the right bank of the Aber Wrach. This megalith is also known as the menhir of Saint-Cava.. We should also mention the covered alley of Lerret in Kerlouan. A little further east, it is important to mention the Cairn of Carn Island, which is not yet drowned, but which is only accessible on foot at low tide.

Cairn on Carn Island, accessible at low tide (© Beynet, 2021)

In the Middle Neolithic, the sea level at this location was 8.80 metres lower than today. At the time of its construction, the primary cairn must therefore have been located on the mainland, about 200 metres from the shore, and overhanging the sea by about 20 metres. It is trapezoidal (Giot, 1987).

In the Gulf of Morbihan, the cromlechs8 on the islet of Er Lannic also bear witness to a time when the sea was lower than today.

These two hemicycles are horseshoe-shaped. Only the upper part of the northern hemicycle is visible today, the rest is submerged. At the time of the construction of these cromlechs, the islet of Er Lannic formed a hill at the foot of which a river flowed. Topographical surveys carried out in 1992 showed that it was made up of 65 menhirs ranging from 1.20 to 4.40 metres in height. These menhirs are arranged side by side. The southern hemicycle, which is immersed, is circular in shape, about 60 m in diameter, with an opening to the east. It is aligned with the sunrise. It is made up of 30 menhirs with an almost constant height of 4m. The two end menhirs are more imposing, one being 8.20m high. They are arranged with regular spaces between them.

Other blocks were found around these two hemicycles. In all, 119 menhirs have been counted on this site. The various excavations carried out - first by G. de Closmadeuc in 1866, then R. Merlet in 1919, and finally Z. Le Rouzic between 1923 and 1926, as well as the 1992 surveys - made it possible to discover that four menhirs bear engravings. Two menhirs bear representations of axes, one menhir bears a series of cupules that may represent the constellation of the Great Bear (according to Z. Le Rouzic), and one menhir bears an engraving composed of four vertical and parallel lines.

The various archaeological elements found during the excavations suggest that the site was occupied around 4000 BC, with the hemicycles being built around 3500 BC. The differences in construction also suggest that the southern hemicycle was built after the northern hemicycle.

The discoveries made during the excavations suggest that the site was used as an axe cutting and polishing workshop and then converted into a burial place and sanctuary, unless the manufacture of axes was considered a sacred act (Sources: Excavations on the site by Messrs Closmadeuc in 1866, Merlet in 1919 and Le Rouzic in 1923-1926, described on the website lieux-insolites.fr9).

In the heart of the Gulf of Morbihan (France), on the island of Gavrinis, is one of the most exceptional prehistoric sites in France: a monumental funerary architecture of dry stones, housing a dolmen. The Gavrinis cairn is now recognised worldwide for the profusion of engraved ornamentation. Built nearly 6,000 years ago, between 4,500 and 4,300 BC - well before Stonehenge, the famous pyramids of Egypt and the Moai of Easter Island - the Gavrinis cairn is the burial place of our distant ancestors.

The Gavrinis cairn is remarkablefor its ornamentation and for its dimensions: more than 50 m in diameter, 6 m high. It offers a multitude of engravings of rare finesse, which cannot be found anywhere else in the world (Source: cairndegavrinis.com website).

Left, Cassini map (18th century), right, staff map (1820-1866) ©IGN

Islands of Gavrinis and Er Lannic in the Gulf of Morbihan (Source: Navionics, do not use for navigation)

Semi-submerged cromlech of the Er Lannic island (© Beynet, 2021)

Er Lannic, seen from Gavrinis island near the Cairn (© Beynet, 2021)

In summary, according to Milanković's theory, the glacial maximum is due to the Earth's position relative to the sun. Its axis of rotation and obliquity, as well as the distance from its star due to the planet's elliptical orbit, reduce the supply of heat and explain the alternating ice ages and periods of warming. The Earth's approach to its sun and a more favourable axis obliquity have caused temperatures to rise between 20,000 and 12,000 years ago, the beginning of the Holocene and our current geological era. As Professor Edouard Bard10 explained:

"From 15,000 years ago, there was a rapid rise in water levels of 40 to 50 mm per year due to the melting of the large North American and Scandinavian ice sheets, followed by a slowdown of 8 to 12 mm per year between 10,000 and 5,000 years ago to reach a quasi-stagnation of 1 mm per year for the last 5,000 years”.

If we go back further in time, for example 125,000 years ago, the Mediterranean Sea level was higher than in our contemporary era. Indeed, according to a recent study11 (Hoffman et al., 2017), 125,000 years ago the sea level was 69 m higher than today, but the surface temperatures of the oceans were similar to what they are today.

“The Eemian interglacial (130,000 - 115,000 years ago) was one of the warmest periods recorded in the last 800,000 years. The warmest peak of the Eemian was around 125 000 years ago. A time that is similar to our own in one respect, since a recent study published in January 2017 in the journal Science and conducted by researchers from Oregon State University now finds that sea surface temperatures (SST) during this last interglacial period were equivalent to the surface temperatures recorded over the last 150 years. Except that at that time, sea levels were 6 to 9 m higher. Using marine sediment cores collected from 83 sites around the world, the researchers were able to reconstruct global ocean surface temperatures during the Eemian. They then matched the data with those covering the years 1870 to 1889 and 1995-2014. Some 129 000 years ago, global sea surface temperatures were already similar to the temperatures for the period 1870-1889. Four thousand years later, however, they had increased by 0.5 degrees Celsius, exactly the same amount as in the years 1995-2014, only 150 years later, the Oregon State University researchers said. The researchers conclude that the estimates of temperature change from climate models are too low. During the Eemian interglacial, the Earth's climate warmed by about 2 degrees due to a change in the planet's tilt, causing sea levels to rise. Today this is not the case, and with the global warming observed today being accelerated by human activities, researchers are concerned about the uncertainty of the consequences of such warming on the oceans today”.

3 At the end of the Miocene, during the Messinian period (from 7.246 to 5.333 million years ago), an event affected the Mediterranean basin: the Messinian Salinity Crisis (MSC). The closure of the strait between the Atlantic and the Mediterranean caused the progressive drying up of the basin. The maximum lowering was by 1500 to 2500 m below the present level, depending on the remaining basins, for about 600,000 years. The CMS forced all surface and groundwater flows to adapt to this very low level. The rivers cut deep valleys far upstream, the Nile to Aswan (Egypt) or the Rhône to Lyon (France). The opening of the Strait of Gibraltar, marking the beginning of the Pliocene, caused the entire basin to be flooded almost instantaneously, favouring a thick sedimentation fed by the rivers.

4 The ecliptic is the great circle representing the projection, on the celestial sphere, of the apparent annual path of the Sun as seen from the Earth.

5 Today, ground uplift is still taking place in the northern half of Sweden due to the melting of the massive glaciers from the last ice age. This ground uplift is the return of the earth's crust to its equilibrium position, after having been loaded with several kilometres of ice during the last ice age. To date, the country has risen several hundred metres and it is estimated that several tens of metres are still to come. (Beynet, 2022d).

6 Note, however, that according to recent papers published by Donald Rapp between 2016-2018 under the title Beyond Milankovitć, the orbital parameters described by the Serbian mathematical astronomer would not be sufficient to explain the cessation of ice ages.

7 About 140,000 years ago, during the Riss Glaciation, the Rhône glacier moved a "big rock" composed of metamorphic triassic quartzite, which is a typical rock of the Haute Maurienne and Haute Tarentaise regions, as far as the present-day city of Lyon. The Croix-Rousse and Fourvière hills in Lyon are covered by Rissian frontal moraines (penultimate Quaternary glaciation), which were deposited at their end by glaciers from the Alps. These moraines contain pebbles of all sizes, including enormous blocks, known as "erratic blocks". Riss’s glacial maximum corresponds to the Alpine glaciers' maximum extension, which reached the site of Lyon, without ever exceeding it. During the last glaciation (the Würm, 18,000 years ago), the Alpine glaciers stopped about 20 km east of Lyon, just before the Saint Exupéry airport. (Thomas, 2003).

8 A cromlech is a prehistoric, megalithic monument consisting of an alignment of vertical monoliths (menhirs), forming an enclosure of raised stones, generally circular. Sometimes a menhir is placed in the centre.

9 See : https://www.lieux-insolites.fr/morbihan/er%20lannick/lannic.html

10 Edouard Bard, professor at the Collège de France and researcher at the Centre de recherche sur les géosciences (CEREGE, Aix-en-Provence).

11 This study was summarised in an article published by science journalist Brice Louvet in January 2017, on the Sciencepost.fr website.