Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get?

Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get? xtock / shutterstock

It took evolution 3 or 4 billion years to produce Homo sapiens. If the climate had completely failed just once in that time then evolution would have come to a crashing halt and we would not be here now. So to understand how we came to exist on planet Earth, we’ll need to know how Earth managed to stay fit for life for billions of years.

This is not a trivial problem. Current global warming shows us that the climate can change considerably over the course of even a few centuries. Over geological timescales, it is even easier to change climate. Calculations show that there is the potential for Earth’s climate to deteriorate to temperatures below freezing or above boiling in just a few million years.

We also know that the Sun has become 30% more luminous since life first evolved. In theory, this should have caused the oceans to boil away by now, given that they were not generally frozen on the early Earth – this is known as the “faint young Sun paradox”. Yet, somehow, this habitability puzzle was solved.

Scientists have come up with two main theories. The first is that the Earth could possess something like a thermostat – a feedback mechanism (or mechanisms) that prevents the climate ever wandering to fatal temperatures.

The second is that, out of a large number of planets, perhaps some just make it through by luck, and Earth is one of those. This second scenario is made more plausible by the discoveries in recent decades of many planets outside our solar system – so-called exoplanets. Astronomical observations of distant stars tell us that many have planets orbiting them, and that some are of a size and density and orbital distance such that temperatures suitable for life are theoretically possible. It has been estimated that there are at least 2 billion such candidate planets in our galaxy alone.

Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get? There are many exoplanets…but how many have a stable climate? Jurik Peter / shutterstock

Scientists would love to travel to these exoplanets to investigate whether any of them have matched Earth’s billion years of climate stability. But even the nearest exoplanets, those orbiting the star Proxima Centauri, are more than four light-years away. Observational or experimental evidence is hard to come by.

Instead, I explored the same question through modelling. Using a computer program designed to simulate climate evolution on planets in general (not just Earth), I first generated 100,000 planets, each with a randomly different set of climate feedbacks. Climate feedbacks are processes that can amplify or diminish climate change – think for instance of sea-ice melting in the Arctic, which replaces sunlight-reflecting ice with sunlight-absorbing open sea, which in turn causes more warming and more melting.

In order to investigate how likely each of these diverse planets was to stay habitable over enormous (geological) timescales, I simulated each 100 times. Each time the planet started from a different initial temperature and was exposed to a randomly different set of climate events. These events represent climate-altering factors such as supervolcano eruptions (like Mount Pinatubo but much much larger) and asteroid impacts (like the one that killed the dinosaurs). On each of the 100 runs, the planet’s temperature was tracked until it became too hot or too cold or else had survived for 3 billion years, at which point it was deemed to have been a possible crucible for intelligent life.

Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get? Climate-altering: the 1991 eruption of Mount Pinatubo in the Philippines blasted so much ash into the atmosphere that global temperatures temporarily dropped by 0.6˚C. SRA Blaze Lipowski / picryl

The simulation results give a definite answer to this habitability problem, at least in terms of the importance of feedbacks and luck. It was very rare (in fact, just one time out of 100,000) for a planet to have such strong stabilising feedbacks that it stayed habitable all 100 times, irrespective of the random climate events. In fact, most planets that stayed habitable at least once, did so fewer than ten times out of 100. On nearly every occasion in the simulation when a planet remained habitable for 3 billion years, it was partly down to luck. At the same time, luck by itself was shown to be insufficient. Planets that were specially designed to have no feedbacks at all, never stayed habitable; random walks, buffeted around by climate events, never lasted the course.

Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get? Repeat runs in the simulation were not identical: 1,000 different planets were generated randomly and each run twice. (a) results on first run, (b) results on second run. Green circles show success (stayed habitable for 3 billion years) and black failure. Toby Tyrrell, Author provided

This overall result, that outcomes depend partly on feedbacks and partly on luck, is robust. All sorts of changes to the modelling did not affect it. By implication, Earth must therefore possess some climate-stabilising feedbacks but at the same time good fortune must also have been involved in it staying habitable. If, for instance, an asteroid or solar flare had been slightly larger than it was, or had occurred at a slightly different (more critical) time, we would probably not be here on Earth today. It gives a different perspective on why we are able to look back on Earth’s remarkable, enormously extended, history of life evolving and diversifying and becoming ever more complex to the point that it gave rise to us.The Conversation

Professor Toby Tyrrell discusses his research.

About The Author

Toby Tyrrell, Professor of Earth System Science, University of Southampton

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Related Books

The Uninhabitable Earth: Life After Warming Kindle Edition

by David Wallace-Wells
0525576703It is worse, much worse, than you think. If your anxiety about global warming is dominated by fears of sea-level rise, you are barely scratching the surface of what terrors are possible. In California, wildfires now rage year-round, destroying thousands of homes. Across the US, “500-year” storms pummel communities month after month, and floods displace tens of millions annually. This is only a preview of the changes to come. And they are coming fast. Without a revolution in how billions of humans conduct their lives, parts of the Earth could become close to uninhabitable, and other parts horrifically inhospitable, as soon as the end of this century. Available On Amazon

The End of Ice: Bearing Witness and Finding Meaning in the Path of Climate Disruption

by Dahr Jamail
1620972344After nearly a decade overseas as a war reporter, the acclaimed journalist Dahr Jamail returned to America to renew his passion for mountaineering, only to find that the slopes he had once climbed have been irrevocably changed by climate disruption. In response, Jamail embarks on a journey to the geographical front lines of this crisis—from Alaska to Australia’s Great Barrier Reef, via the Amazon rainforest—in order to discover the consequences to nature and to humans of the loss of ice.  Available On Amazon

Our Earth, Our Species, Our Selves: How to Thrive While Creating a Sustainable World

by Ellen Moyer
1942936559Our scarcest resource is time. With determination and action, we can implement solutions rather than sit on the sidelines suffering harmful impacts. We deserve, and can have, better health and a cleaner environment, a stable climate, healthy ecosystems, sustainable use of resources, and less need for damage control. We have so much to gain. Through science and stories, Our Earth, Our Species, Our Selves makes the case for hope, optimism, and practical solutions we can take individually and collectively to green our technology, green our economy, strengthen our democracy, and create social equality. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

YOU MAY ALSO LIKE

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook icontwitter iconyoutube iconinstagram iconpintrest iconrss icon

 Get The Latest By Email

Weekly Magazine Daily Inspiration

LATEST VIDEOS

The Great Climate Migration Has Begun
The Great Climate Migration Has Begun
by Super User
The climate crisis is forcing thousands around the world to flee as their homes become increasingly uninhabitable.
The Last Ice Age Tells Us Why We Need To Care About A 2℃ Change In Temperature
The Last Ice Age Tells Us Why We Need To Care About A 2℃ Change In Temperature
by Alan N Williams, et al
The latest report from the Intergovernmental Panel on Climate Change (IPCC) states that without a substantial decrease…
Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get?
Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get?
by Toby Tyrrell
It took evolution 3 or 4 billion years to produce Homo sapiens. If the climate had completely failed just once in that…
How Mapping The Weather 12,000 Years Ago Can Help Predict Future Climate Change
How Mapping The Weather 12,000 Years Ago Can Help Predict Future Climate Change
by Brice Rea
The end of the last ice age, around 12,000 years ago, was characterised by a final cold phase called the Younger Dryas.…
The Caspian Sea Is Set To Fall By 9 Metres Or More This Century
The Caspian Sea Is Set To Fall By 9 Metres Or More This Century
by Frank Wesselingh and Matteo Lattuada
Imagine you are on the coast, looking out to sea. In front of you lies 100 metres of barren sand that looks like a…
Venus Was Once More Earth-like, But Climate Change Made It Uninhabitable
Venus Was Once More Earth-like, But Climate Change Made It Uninhabitable
by Richard Ernst
We can learn a lot about climate change from Venus, our sister planet. Venus currently has a surface temperature of…
Five Climate Disbeliefs: A Crash Course In Climate Misinformation
The Five Climate Disbeliefs: A Crash Course In Climate Misinformation
by John Cook
This video is a crash course in climate misinformation, summarizing the key arguments used to cast doubt on the reality…
The Arctic Hasn't Been This Warm For 3 Million Years and That Means Big Changes For The Planet
The Arctic Hasn't Been This Warm For 3 Million Years and That Means Big Changes For The Planet
by Julie Brigham-Grette and Steve Petsch
Every year, sea ice cover in the Arctic Ocean shrinks to a low point in mid-September. This year it measures just 1.44…

LATEST ARTICLES

image
Why the UK is so unprepared for the impacts of climate change
by Liam F. Beiser-McGrath, Lecturer (Assistant Professor) in Politics and Director of the PECC Lab, Royal Holloway University of London
The UK is woefully unprepared for the dangers of climate change according to a report from the Climate Change Committee…
Rows of solar panels are separated by a walkable space between them
Solar power and energy storage combo boosts reliability
by Matt Shipman-NC State
New research shows that when a power system combines energy storage and solar power generation, the end result is…
Climate change: what G7 leaders could have said – but didn't
Climate change: what G7 leaders could have said – but didn't
by Myles Allen, Professor of Geosystem Science, Director of Oxford Net Zero, University of Oxford
The four-day G7 summit in Cornwall ended with little cause for celebration from anyone worried about climate change.…
How world leaders' high-carbon travel choices could delay climate action
How world leaders' high-carbon travel choices could delay climate action
by Steve Westlake, PhD Candidate, Environmental Leadership, Cardiff University
When UK prime minister Boris Johnson took a one-hour flight to Cornwall for the G7 summit, he was criticised for being…
Maggot burgers can help to solve world hunger
by Paul Brown
Fancy maggot burgers for dinner? Eating animals and plants which revolt many of us could cut hunger caused by climate…
The idea of green growth'is flawed. We must find ways of using and wasting less energy
by Michael (Mike) Joy, Senior Researcher; Institute for Governance and Policy Studies, Te Herenga Waka — Victoria University of Wellington
As countries explore ways of decarbonising their economies, the mantra of “green growth” risks trapping us in a spiral…
Four reasons why G7 climate finance initiative will struggle against China's Belt and Road
Four reasons why G7 climate finance initiative will struggle against China's Belt and Road
by Karen Jackson, Senior Lecturer in Economics, University of Westminster
During the G7 summit in Cornwall, the group of nations unveiled a global initiative to help low and middle-income…
image
Electric heat pumps use much less energy than furnaces, and can cool houses too – here's how they work
by Robert Brecha, Professor of Sustainability, University of Dayton
To help curb climate change, President Biden has set a goal of lowering U.S. greenhouse gas emissions 50%-52% below…

 Get The Latest By Email

Weekly Magazine Daily Inspiration

New Attitudes - New Possibilities

InnerSelf.comClimateImpactNews.com | InnerPower.net
MightyNatural.com | WholisticPolitics.com | InnerSelf Market
Copyright ©1985 - 2021 InnerSelf Publications. All Rights Reserved.