00:00It's about 12900 years ago,
00:02I wasn't here, but something has pushed the north to the glacier.
00:07For years, scientists had thought that an enormous asteroid was the cause.
00:12But new research points towards something already on Earth.
00:17A volcano hiding under the ice, or under the water,
00:20which, instead of falling the ice,
00:22made the opposite and made the Groenland even more cold.
00:27The scientists call this brutal gel the Dryas recent.
00:32Malgré the appearance, with its snowstorms insupportable everywhere in the world,
00:37the Earth is technically still in an air glacier.
00:40The orbit and the axis of the Earth have all sorts of inclinations and oscillations.
00:45Therefore, we alter between cold and cold periods and cold periods.
00:50In this moment, we are in an interglacial period called the Holocene.
00:55But before the civilizations could really cultivate and take advantage of the summer,
00:59they had to endure this gel inattend,
01:02which has lasted about 1300 years.
01:06The data from Groenland
01:07suggest that this change was only produced in a few decades.
01:11The temperatures have fallen from 15 degrees Celsius,
01:14the winds have been strengthened,
01:16and all the North Atlantic Atlantic has been working as if someone had pushed the congélator
01:21at a point.
01:22In the European sediment,
01:24the forest trees are coming back to the tundra of cold weather.
01:28This sinking has even brought a small Arctic flower resistant,
01:32the Dryas,
01:32in the middle of the Europe.
01:34And it's here that this cold wave of cold,
01:36suddenly,
01:36to you,
01:37it takes its name.
01:38But why this cold inattend?
01:41The indices
01:42is at the core of the glacier glacier
01:44of Groenland.
01:45All this ice is like the hard disk of the Earth,
01:48with all the events placed in order.
01:52When it neige at Groenland,
01:53the neige does not really.
01:55In other words,
01:56each year,
01:57the neige accumulates on top.
02:00With the time,
02:02all this weight comprise the lower layers
02:03and transform the glass.
02:05This process is
02:07imprisoning the minuscule bubbles
02:08containing fragments of the atmosphere.
02:11In general,
02:12the gel
02:12conserve an instantane
02:13of what happened in the sky
02:15at this moment.
02:17For example,
02:18if there was a big forest forest
02:20in Canada,
02:20five thousand years ago,
02:22the smoke and the smoke
02:23would have arrived
02:24to the Groenland
02:25to be placed on the neige.
02:27If a big impact of asteroids
02:29had really produced
02:30at this time,
02:31we would expect to find
02:32its chemical traces
02:33in the corresponding clouds
02:34of glass.
02:35For access to these data,
02:37scientists use
02:38enormous creuses
02:40in deep depth
02:42and extract
02:43long cylinders
02:44called the glass of glass.
02:46And as the glass
02:47of Groenland
02:48is about 3 km
02:49of the stars,
02:50these carottes
02:51preserve a climate
02:52that is incredibly long
02:54that allows
02:54to examine
02:55the glass
02:55of over 100 000 years old.
02:58In examining
02:59the glass of glass
03:00of this period,
03:01researchers discovered
03:02a sudden peak
03:03of platinum.
03:04This element
03:05is extremely rare
03:06near the surface
03:07but more famous
03:09in the meteorites
03:10and asteroids.
03:11That's why
03:12the theories point
03:13towards something
03:14enormous
03:14from the space.
03:15But how
03:17a asteroid
03:17could cause
03:18a climate change?
03:20In general,
03:21it works like that.
03:22Imagine
03:22a giant rock
03:23comet
03:24comet
03:24comet
03:24a glacier
03:25The impact
03:26project
03:26and all kinds
03:29of particles
03:29very high
03:30in the sky,
03:31above the clouds.
03:32The big impacts
03:33can cause
03:34massive incendies
03:35adding even more
03:37of smoke.
03:38The planet
03:38is surrounded by
03:39a cloud
03:39of smoke
03:40which blocks
03:42a part of the solar energy
03:43The problem
03:44with the glass
03:45is that when they
03:46do not
03:46they end
03:47and turn the light
03:48into the space
03:49which frees
03:50even more.
03:51This loop
03:52is called
03:53the retroaction
03:54glass
03:54albedo.
03:55A surprising theory
03:57for the recent
03:57and to make it even
03:59more tentative
04:00the Groenland
04:01seems also
04:02to hide the real crater.
04:05The radar
04:06under the glacier
04:07Iyawata
04:08revealed
04:09a circular structure
04:10of about 31 km
04:11of diameter.
04:13The scientists
04:14wondered
04:14if he was
04:15the responsible
04:15of the DRIAS
04:16recent
04:17but the adaptation
04:18showed that
04:18he was
04:19about 58 millions
04:20of years
04:20too old
04:21to be the coupable.
04:23And then,
04:24a peak of platinum
04:25doesn't necessarily mean
04:25a meteorite.
04:27The platinum
04:28of space
04:28is generally
04:30accompanied
04:30of an ally
04:31of an ally
04:31of the iridium.
04:32If we found
04:33one,
04:34we should find
04:34the other.
04:35But when scientists
04:37analyzed the glass
04:38of Groenland
04:39was absent.
04:41So,
04:41the chemical
04:42doesn't really
04:42point out
04:42to the meteorite.
04:44It looks like
04:45the volcanic
04:46of the Atlantic
04:47North.
04:48Then,
04:49there is
04:49the form
04:49of the platinum signal
04:50of platinum.
04:51It's been
04:52several years,
04:53not a single
04:53cloud net
04:54of explosion.
04:58So,
05:02if the platinum
05:02doesn't
05:03point out
05:03to the
05:03planet,
05:04the question is
05:05simple.
05:06What is
05:06on the planet?
05:07the sea
05:07of the sea
05:09and also
05:10refroid
05:10the planet?
05:12The answer is
05:14a volcano.
05:15The volcano
05:16would have been
05:16in the Atlantic
05:17North,
05:18perhaps in Iceland,
05:19and it was
05:20perhaps not
05:21on the ground
05:22It could enter
05:23in eruption
05:24under a heavy
05:24glass or
05:25below.
05:27Here is the difference.
05:29When a volcano
05:30explodes
05:30at the air free,
05:31we obtain
05:31the lava waves
05:33but,
05:34sous the ice,
05:35the magma
05:36meets the water
05:38immediately
05:39in vapor
05:40and can explode
05:41in fine sand
05:42and in gas.
05:43sous l'eau,
05:44de puissantes éruptions
05:45peuvent aussi fragmenter
05:47le magma
05:47et propulser
05:48des matériaux
05:49vers le haut.
05:50Dans les deux cas,
05:51le vrai problème,
05:52ce n'est pas la roche
05:53en fusion,
05:53c'est le gaz.
05:55Ça, je connais.
05:56Les grandes éruptions
05:58comme celle-ci
05:58crachent des quantités
05:59massives de dioxyde
06:01de soufre.
06:01Si ce gaz monte
06:02assez haut,
06:03à des kilomètres
06:04au-dessus des nuages,
06:05il se disperse
06:06et se mélange
06:07à la vapeur d'eau
06:08pour créer des aérosols
06:09sulfatés.
06:11Ce sont en fait
06:12des gouttelettes microscopiques
06:14d'acide sulfurique.
06:15Individuellement,
06:16elles sont invisibles,
06:17mais des milliards
06:18ensemble
06:19forment un véritable
06:20parasol planétaire.
06:22Depuis l'espace,
06:23la Terre paraît plus brillante
06:24parce que ses gouttelettes
06:25réfléchissent la lumière
06:26du Soleil.
06:28Mais ici,
06:29au sol,
06:30c'est comme regarder le Soleil
06:31à travers un fin voile
06:32argenté.
06:33Pas besoin d'obscurité totale
06:35pour geler le monde,
06:36il suffit de tamiser
06:37un peu le Soleil.
06:38Les étés ne sont plus
06:40vraiment chauds
06:41et la neige persiste
06:42jusqu'en juillet.
06:44Cette neige résiduelle
06:45se compacte en glace
06:46qui réfléchit encore
06:47plus de lumière solaire.
06:49C'est le même type
06:50de boucle de rétroaction
06:52que celle déclenchée
06:53par un astéroïde.
06:54Sauf que dans ce cas,
06:55le Soleil est bloqué
06:56par la poussière
06:57alors qu'ici,
06:58il est renvoyé
06:59dans l'espace.
07:00Quelque chose de similaire
07:01s'est produit assez récemment.
07:03En 1991,
07:05le mont Pinatubo,
07:06aux Philippines,
07:07a déversé environ
07:0820 millions de tonnes
07:09de dioxyde de soufre
07:11dans la stratosphère.
07:12La Terre s'est retrouvée
07:14sous un fin voile
07:15et les températures mondiales
07:16ont baissé d'environ
07:171,5 degrés Celsius
07:19pendant près de deux ans.
07:20Imaginez l'ampleur
07:21de l'éruption
07:22si les températures
07:23au Groenland
07:24avaient chuté
07:25de plus de 15 degrés Celsius
07:26et étaient restées
07:27aussi basses
07:28pendant 1200 ans.
07:30Mais voici une question intéressante.
07:32Et si ce n'était
07:33ni l'un ni l'autre ?
07:35Ni un astéroïde
07:36modifiant le climat
07:37ni un volcan caché.
07:39Il y a un troisième suspect,
07:40bien plus discret,
07:42mais tout aussi dangereux.
07:43L'eau douce.
07:45Une théorie majeure
07:46est que le monde
07:47s'est réchauffé
07:48et qu'un immense
07:49lac glaciaire
07:50en Amérique du Nord,
07:51souvent associé
07:51au lac Agassiz,
07:53s'est soudainement vidé
07:54ou a changé de cours,
07:55déversant
07:56une quantité absurde
07:57d'eau douce.
07:58Des millions
07:59de milliards de litres
08:00dans le système
08:01de l'Atlantique Nord.
08:02Cette eau douce
08:03a dilué
08:04l'océan de surface
08:05dans les régions
08:06où l'eau dense
08:07et salée
08:07plonge normalement
08:09et alimente
08:09la circulation atlantique
08:11à grande échelle.
08:12Quand cette plongée
08:13faiblit,
08:14la circulation globale
08:15ralentit
08:16et moins de chaleur océanique
08:18atteint l'Atlantique Nord.
08:19Avec ce système perturbé,
08:22l'hémisphère Nord
08:22pouvait se refroidir
08:23extrêmement vite
08:24à l'échelle climatique.
08:26En quelques années,
08:28à quelques décennies,
08:29plutôt qu'en siècles.
08:31Dans cette version,
08:31le pic de platine
08:33pourrait être
08:33une coïncidence,
08:34un rau volcanique
08:35pendant le gel,
08:36pas le déclencheur.
08:38Et au final,
08:40si le volcan
08:40était la cause
08:41de cet hiver sans fin,
08:42cela pourrait-il
08:43se reproduire de nos jours ?
08:45Absolument.
08:47La région de l'Atlantique Nord
08:48est toujours
08:49géologiquement active.
08:51L'Islande
08:52entre régulièrement
08:52en éruption
08:53et les systèmes volcaniques
08:54le long de la dorsale
08:55médio-atlantique
08:56sont bien vivants.
08:58Mais ce ne serait pas
08:59une surprise
08:59venue de nulle part.
09:01Même les volcans
09:01enfouis sous la glace
09:02donnent généralement
09:03des signes avant-coureurs,
09:04comme des séismes.
09:06Si la chaleur
09:07s'accumule en profondeur,
09:08elle peut faire fondre
09:09d'importants volumes
09:10de glace par en dessous
09:11avant que quiconque
09:12ne voit de la cendre
09:13dans le ciel.
09:13D'un autre côté,
09:15il n'y aurait pas besoin
09:16d'une éruption
09:16cataclysmique.
09:18Une explosion modérée
09:19injectant du soufre
09:20eau dans la stratosphère
09:22pourrait assombrir
09:23le soleil
09:23pendant quelques années,
09:24comme le Pinatubo
09:25l'a fait.
09:26Cela ne veut pas dire
09:27qu'une nouvelle ère
09:28glaciaire
09:29débuterait le lendemain.
09:30Le contexte climatique
09:31actuel est très différent
09:33de celui
09:33d'il y a 12 800 ans.
09:35Mais le mécanisme
09:36est réel.
09:38L'atmosphère
09:38peut encore être déstabilisée.
09:40Et parfois,
09:41il suffit d'une éruption
09:42cachée.
09:43C'est parti.
09:44C'est parti.
09:44C'est parti.
09:44C'est parti.
09:44C'est parti.
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