How hot earth can get... | connecting-the-dots

The rise of Oxygen as recorded in the rock

Photosynthetic microbes, which release oxygen, became abundant in the ocean a couple billion years ago.
Colorful slabs of rock called Banded Iron formations formed on the sea floor when oxygen reacted with dissolved iron in the sea.
The reactions created iron oxides that sank to the seabed to form red sheets interspersed with layers of silica rich sediment.

Permian Period

Mass extinction, ended in fire

some 270 million years ago, all animal life on Earth very nearly ended in a catastrophic mass extinction accompanied by intense, rapid global warming.
The period ended in fire.

Snowball effect

The polar ice caps crept down to the equator and the planet froze over in stakes known as "Snowball Effect", which each lasted for millions of years.

Hadean Eon - Hell on Earth

Lasted till 4 billion years ago

Began some 4.6 billion years ago and last till 4 billion years ago

Peak temperatures

It got a lot hotter, with peak temperatures being approximately 10,000 degree celsius ie. 18,000 degree fahrenheit
Its climate influences are in the form of planetary collisions and primordial heat.

Theia smacked into Earth

About 100 million years later, Mars sized rock called Theia smacked into the young earth.
This released the energy equivalent to trillions of H bombs.
Left the ocean of magma beneath the sky of rock vapor.
No part of the earth would ever have subsequently reached more than about 7,000 kelvins or about 6,700 degree celsius.

Moon heated earth via gravitational forces

The freshly formed moon heated earth via gravitational forces
Earth's interior molten for years , magma ocean finally crystallised into rock.

Sun - Earth's most important source of energy

Sun overtook as earth's most important source of energy.

Archean Eon - Earth's Thermostat turns on

2.5 billion years ago, 40 degree celsius

It lasted from 4 billion to 2.5 billion years ago.
The average temperature was between the range of 0 to 40 degree celsius ie. 32 to 104 degree fahrenheit

Greenhouse effect and carbon cycle

The major climate influencers were greenhouse effect and carbon cycle.

Raining started

As the Hadean earth cooled, it started to rain.
Water vapour poured out of atmosphere until the Earth's surface drowned beneath a global ocean.
Land first peeked above the seas in arcs of volcanic islands

Perfectly habitable

The earth became perfectly habitable, the earliest signs of life date to this period.
Climate conundrum started

Sun - 70% brighter as of today

The sun was only about 70 to 80% as bright as it is today. The sun's energy comes from the fusion of hydrogen to helium. As hydrogen gets used up, the core gets denser, which speeds up fusion and makes the sun brighter and hotter over time. The energy coming from the faint young sun on its own would not have been enough to keep the planet as warm as it was. So, in theory, Earth should have transformed into the ninth circle of Dante's hell - iced over.

Heat trapped like a blanket

Greenhouse gases like carbon dioxide and methane allowed sunlight to beat down on earth's surface, which heats it up but don't allow heat to radiate back our as infrared light. This traps heat around Earth like a blanket. Bigger greenhouse effect than today.
Hadean magma ocean cooled, outgassed a thick steamy atmosphere rich in water vapour and carbon dioxide. Temperatures could have been around 200 degree celsius.
Between the hellish Hadean and clement Archean, the planet's natural thermostat came online, the carbon cycle.
Atmospheric carbon dioxide gets transformed into chalky white carbonate minerals through chemical weathering.
Traps carbon dioxide in rock but it doesn't stay trapped forever. Earth constantly recycles its surface into the interior through plate tectonics.
Carbonates end up in the mantle, eventually break down and get belched back up by volcanoes as carbon dioxide.
This cycle is sensitive to temperature.
Chemical weathering speeds up in warm climates and slows down in cold ones.
Beginning of the Archean, the carbon cycle locked away enough carbon dioxide to bring the planet's surface temperature into a habitable range.
With carbon dioxide levels between 10 and 1000 times as high as today and methane levels 100 to 10,000 times high, the Achaean earth was alien but livable.
The geologic thermostat has regulated Earth's temperature ever since and never once has it gotten hot or cold enough to end all life.

Ice planet

The first snowball earth happened between 2.4 billion years to 2.1 billion years ago
The average temperature during this time was - 50 degree celsius or - 58 degree fahrenheit
Near the beginning the Proterozoic eon, earth froze over.
Temperatures stayed low for tens of millions of years, witnessing earth's one of first mass extinctions, with casualties only microbes and no fossils remain to record the death toll.
Sparkling white ice is more reflective than land or seawater. The more ice grows, the more sunlight earth reflects. This increase in reflectivity or albedo, lowers temperatures, encouraging more ice to form in a positive feedback loop
Volcanoes keep pumping carbon dioxide into the atmosphere, the greenhouse effect will thaw out the planet.
Ice melts, the planet becomes less reflective, the planet warms even more and then more ice melts.
Glacial rock deposits left behind in areas that were near the equator back then.
Oceans bloomed with photosynthetic organisms, more and more oxygen rose into the air, which oxidized the methane, which had served as an atmospheric blanket keeping earth warm for 1.5 billion years.

Permian extinction - Deadly global warming

This happened 252 million years ago
The peak temperature was 73 degree celsius or 163 degree fahrenheit
The climate influencers are volcanic eruptions, position of the continents
The end of the permian period, with the super continent pangea would have been a good setting for a western.
Day time air temperatures in the tropics hovered around 50 degree celsius.
The mass extinction, the worst our planet has ever seen.
While the marine ecosystems initially remained unscathed, they were ultimately hit hardest.
[!] 95% of the marine and 75% of the terrestrial species disappeared.
About 300,000 years before the peak of the extinction, volcanoes in Siberia erupted non stop for 1 million years, called the Siberian Trap.
With all lava came lots and lots of carbon dioxide.
The average temperature of the surface soared by up to 10 degree celsius to around 30 degree celsius.
Oceans sweltered, marine life suffocated, bacteria thrived in the anoxic depths poisoned the water with hydrogen sulphide.
Volcanic gas mixed with water to rain acid on the barren, dusty wastes.
It took life 5 million years or more to recover.
"Icehouse" periods, when earth has polar ice are few, and far between.
Previous icehouse, at the time of early premian, the average temperature was 15 degrees celsius cooler than today. Ice sheets reached mid latitudes. It lasted for 105 million years.
Scientists still aren't exactly sure why earth stayed so cool for so long?
90% of all coal deposits date back to this time. We don't know why this ice age begin. we do know how it ended - the greatest mass extinction of all time.

The warmest living world

The cretaceous hot greenhouse extended for 94 million to 82 million years ago
The peak average temperature was 36 degree celsius or 97 degree fahrenheit
The climate influences was greenhouse gases.
During this time, the world was a verdant jungle
The earth was hottest ever since the evolution of life more complex than a microbe. Scientist's aren't sure what drove temperatures so high.
Earth never really cooled down after the permian extinction. The poles were effectively ice free for the entirety of the dinosaurs' nearly 180 million year reign, global mean surface temperatures remained above 20 degree celsius, that is 5 degree hotter than 2024.

Into the future

For the last 2.3 million years, the climate has swung to the rhythm of several long term variations in earth's orbit.
These Milankovitch cycles subtly change the amount of sunlight earth receives and where it is distributed.
At first, every 40,000 years, and later every 100,000 years, earth has cycled between clement interglacial periods and frosty glacial periods some 5 degree celsius cooler.
Due to the rise of the himalayas, which exposed an enormous amount of fresh rock to chemical weathering, atmospheric carbon dioxide levels steadily declined.
By 34 million years ago, Antarctica was cold enough for permanent ice to collect at the south pole.
By 800,000 years ago, carbon dioxide levels dropped to below bout 300 parts per million.
Industrial carbon emissions and gas fueled cars doubled the carbon dioxide level from 280 ppm to 426 ppm.
Average temperature has ticked up by 1.47 degrees celsius.
Carbon dioxide levels will reach 600 ppm by 2100 or soar above 1,000 ppm.
This could result in 4 degree celsius of warming relative to the pre industrial average temperature.
A period of 55 million years ago called Paleocene - Eocene Thermal Maximum (PETM), offers a view on a world with carbon dioxide levels that high. It was the hottest period in the history of our earth.
Leading up to the PETM temperatures rose between 5 to 8 degrees celsius to an average of up to 34 degree celsius.
PETM didn't see a mass extinction , but it did reshuffle ecosystems. Local extinction were common. We would have to migrate to poles to survive.
By 2500, 40% of all land area will have become unsuitable for its current biome.
Earth's history shows that the planet will recover.
Life will go on, with or without us.
Chemical weathering speeds up when it is hot, Earth's natural thermostat has trapped more and more carbon dioxide in rock
It will keep doing that as the sun continues to heat.
That will be a problem for plants, if carbon dioxide gets too low, they can't photosynthesize
500 million years from now, atmospheric carbon dioxide will dip below 100ppm, low enough to kill 95% of plants alive today
1 billion years from now, carbon dioxide will sink even lower, the sun will be about 10% brighter than today and the remaining 5% plants will also disappear.
Oxygen will rapidly disappear from the atmosphere if plants cease to exist.
Earth will spend about 3 years as a hell scape before the sun starts dying and takes out planet with it.

Average global surface temperature over last 485 million years