Is this state of Earth possible, after humans left for a million years?

It is the year 4056 (or probably later). The rocket with the last residents of Earth just took off, because global warming and pollution couldn't be stopped nor reverted and Earth became uninhabitable. The human civilization leaves our solar system to live in space and search for a new planet to exploit. They travel on their mothership for a million years (this timespan can also be changed to get as close as possible to my desired scenario) until they decide to revisit and possibly resettle Earth.

What I want Earth to look like:

• 98% of all the landmass is wasteland/desert
• There are only two climate zones, hot and dry around the equator and cold and dry on the poles
• The two poles are some big chunks of ice, each covering about 20% of Earth's area
• Ocean level is about same as today and still contain some life down really deep, but all the streams are dead
• The atmosphere is still intact, but with more $$CO_2$$ and not much $$O_2$$ left
• There are no animals (at least not so big that a human eye can see it) and no flora
• There is no weather. Little to no wind, rain only arises and goes off over the ocean

The humans plan to terraform and repopulate earth with plants and animals they have saved on their mothership a long time ago.

Is this state of Earth possible or do I overlook some logical errors? What other effects would this state cause, which I have not considered yet?

• Have you seen Wall-E? – WBT May 9 '19 at 13:53
• Is the million years literal or figurative? What most people don't get about "climate change" is that it affects people much more than it affects the planet. Having had life once, it's really, really, really hard to not get life again. the planet, therefore, is perfectly capable of fixing itself (we keep yelling "save the planet!" when in reality it's "save the people!" but that's not as politically sexy). After a million years of no-human-to-screw-things-up, I'd expect the planet to be a Garden of Eden. – JBH May 9 '19 at 14:23
• This 'man made Earth uninhabitable' theme we see a lot of makes no sense. Earth would have to be really, really bad before it made sense to move everyone to even less habitable planets and/or the void of space. If you need a self contained habitat in space, why not build it on Earth and still have normal gravity? – GrandmasterB May 9 '19 at 15:59
• I always want to frame challenge stories like this. Living in space is about being smart with the resources you have, recycling as much as possible and not wasting energy. If your race of people can't do those same exact things with a whole planet of resources backing them, they are totally dead on a spaceship, no matter how big. – Muuski May 9 '19 at 22:56
• Maybe there are giant worms... that live in the sand, and lock up all the water. – Brizzy May 10 '19 at 3:25

•98% of all the landmass is wasteland/desert

•The two poles are some big chunks of ice, each covering about 20% of earths area

This is rather confusing. Yes, I get that there are also cold deserts, but next to the glacier there will be the melting zone, where the bonanza of water will inevitably favor life.

•There are only two climate zones, hot and dry around the equator and cold and dry on the poles

You can hardly get a step like transition from hot and dry to cold and dry. You will have a region where there is an intermediate.

•Atmosphere still intact, but with more $$CO_2$$ and not much $$O_2$$ left

With no photosynthetic organisms, it makes sense that the oxygen will not be available in its unbound state. However, the higher level of carbon dioxide means that the planet is a giant greenhouse. I am not sure liquid or solid water would be possible. And water vapor is also a greenhouse gas. So, forget about the cold, and possibly about the dry. Think something like Venus, without the sulphuric acid.

•There is no weather. Little to no wind, rain only arises and goes off over the ocean.

This is straightforward impossible: if you have an atmosphere, you have weather. It might be dull and monotonous with little variation, but still there will be weather.

• So basically I have to choose between a state that is more like Mars that has all its fluid in the poles and little to no athmosphere or something that is like a nontoxic Venus with a high athmospheric pressure? – Gistiv May 9 '19 at 7:41
• (+1) Also, high $CO_2$ and ice in the poles are going to be impossible to conciliate. Just a little global warming of two or three degrees is going to melt them down - Earth hasn't had ice caps for most of its life. – Rekesoft May 9 '19 at 8:45
• Also large polar ice caps has to take water from somewhere, so essentially the sea level will probably drop significantly to meet the polar caps criterion. – Ister May 9 '19 at 15:38
• it seem impossible that all photosynthetic life disappears. at least algae should flourish in the oceans and drive down the co2. – ths May 9 '19 at 19:35
• could it be possible for dry ice to form at the poles? – Reed May 9 '19 at 20:41

You're positing a world that has no surface plants. That's... implausible.

There are plants out there that can manage climatic extremes far worse than anything humans could live through. Plants actively thrive in concentrations of CO2 that humans would find lethal. You might easily have a massive die-off as climate change modified local conditions, but that's going to be "large fractions" rather than "absolutely everything". Some sort of plant life will survive that die-off and start expanding again to fill the available space.

You're also positing no weather. That is likewise implausible. As long as the earth is running off of solar power, there's going to be heat differentials. Certain chunks of earth will get more or less, for various reasons. That will cause high and low pressure zones, which will cause wind, which will move atmospheric water around, which will result in precipitation falling over land. If anything, we'd expect that climate change would make the weather more chaotic, rather than less.

• People frequently forget just how durable life is. Just about anywhere we've looked, if there's liquid water and an energy source, there's life. We've found bacteria on the edges of undersea volcanic vents, digesting sulfur compounds for energy. We've found fungus growing on the core of the Chernobyl reactor, using gamma radiation for photosynthesis. The hardest part of searching for life on Mars is making sure Earth life doesn't hitch a ride on the sensors and produce a false positive. It's hard to produce an extinction event. – Mark May 9 '19 at 21:25
• Huh. Radiotropic fungus. You learn something new every day. – Ben Barden May 10 '19 at 15:48

The surface conditions you're describing are closer to an ice age than any other situation. In practice the ice caps covered only 35% of the land mass, though they locked up the vast majority of the fresh water. This means that the ice age was one of the driest periods in the planet's history.

The more of the water that's locked up in the poles the drier the rest of the world is. The "temperate" regions become tundra at best, and the rest is largely barren.

Hence the two parts of your problem, the atmosphere and the surface, are in contradiction as the atmosphere effects point to runaway global warming, the surface is global cooling.

No.

The mass extinction you're hoping for—no plants and only microscopic animals—is impossible from these conditions.

At the point that humans left the planet, it was possible for animal and plant life to exist, even if it was limited to certain areas. Because otherwise, they'd be dead before they left.

Once humans were gone, they stopped their industrial activities that caused the pollution and climate change to begin with. In fact, your question implies that they stopped that stuff earlier: "global warming and pollution couldn't be stopped nor reverted." They tried but the climate had reached a tipping point. There were likely some industrial activities or fires that continued after they were gone, but that would have been a blip when you're talking about a million years.

Basically, once humans left, the Earth could begin to heal. For excellent explanations of the mechanisms here, with great detail over multiple areas, check out Alan Weisman's book The World Without Us.

Even with massive unstopped climate change, even with toxic air and water and soil, some plants and animals would survive. Mass extinction doesn't mean total extinction. It can't, not without science fiction world-killing technology.

After a million years, plants and animals would once again populate most of the Earth, land and water.

• The World Without Us is one of the most hopeful books I have ever read. – gerrit May 10 '19 at 14:58
• @gerrit It's one of my favorites. Certainly on my top 10 list of nonfiction books everyone should read. – Cyn says make Monica whole May 10 '19 at 15:01
• Ocean level is about same as today and still contain some life down really deep, but all the streams are dead

Neither of these statements make sense. Currently, about 10% of the planet is covered with ice (polar ice caps plus glacial ice) and the sea level is where it is. During the most recent ice age, the planet was covered to about 30% with ice. The sea level then was about 120m lower than it is today. You're proposing ice sheets even bigger. The sea level will be correspondingly lower.

As for all streams being dead, this is not possible in your scenario. As L. Dutch said: "next to the glacier there will be the melting zone, where the bonanza of water will inevitably favor life." This melting zone will be the home of a whopping big glacial melt water lake. During the last ice age, this was Lake Agassiz. And from that lake will flow huge rivers. Quite lively!

First of all, ice sheets are good scouring pads: they will essentially destroy and push most of the environmental damage away, heaping it up in the lands at their maximum extent. The Laurentide Sheet got as far south as Kentucky and Pennsylvania last time around. This time, with your proposed larger coverage, it will probably be somewhere in the region of Oregon, Tennesse and North Carolina. In Europe, last time around, the ice covered the UK, northern Germany, Poland, half of Ukraine and most of Russia. This time, maybe include northern France, all of Germany, Romania, all of Ukraine.

They travel on their mothership for a million years (this timespan can also be changed to get as close as possible to my desired scenario) unitl they decide to revisit and possibly resettle earth.

One thing to consider here is that ice ages come and go. We're actually still in the middle of an ice age now; it's just that we happen to be blessed to live in an interglacial period, and a million years is a long time. The present Quaternary Glaciation began about 100000 years ago. There could be several "ice ages" during the time frame you posit. In all that time, I find it extremely unlikely that Earth will be "uninhabitable" for very long.

All in all, while it's an interesting scenario, I'd say Reality Check on this =

FAIL

Too many severely destructive actions would have to be carried out before your scenario becomes plausible. And that's to say nothing of the clearly impossible conditions you set (like no weather).

• Is it possible that (because the ice sheets completely melted and then reformed) the ice is much thinner, though it covers a larger area, so the total volume of ice is about the same, leading to similar sea level? – prl May 9 '19 at 15:01
• @prl -- A good question which I'm not knowledgeable enough to answer. Will leave that to an expert! If the overall climate is colder, then I would think snow and ice cover might be broader but relatively thin. But the OP does say "big chunks of ice" which to me is more evocative of glaciers and ice sheets. – elemtilas May 9 '19 at 15:33

I agree with Dutch's answer in the main, but there is an important element that is not discussed in his answer which I want to bring up; Thermal Mass.

Put simply, thermal mass is the same as a heat sink; it absorbs heat readily and in massive quantities, releasing it over time when the ambient temperature is lower. The earth is mostly covered in one of the best heat sinks we know of;

Water.

This is important because we think of deserts as being always hot, but they're not. During the night, deserts tend to get very cold because there's nothing (much) in them that has retained the heat during the day. This is also the reason why coastal regions tend to have more temperate climates than drier inland environments. The sea retains a lot of heat during the daytime, making the environment seem cooler than it should, and releases it through the night, making it feel warmer than it should. In practice, this smooths out the temperature variation between day and night.

In that respect, it is possible for you to have two 'biomes'; hot and dry would be the day, and cold and dry would be the night. The catch is that the ice at the poles would put paid to that climate model, meaning that you can only have one or the other; either hot days cold nights and no water, or plenty of water in reserve (albeit in ice), and no sudden changes between temperature during day and night.

The Permian-Triassic Extinction Event (AKA End-Permian Event or The Great Dying) is the largest known extinction event, occurring 250 million years ago. An estimated 96% of all on earth was wiped out in this event (The K-T extinction, aka The Dinosaur One, by comparison, was 75% of all life). While it is still unknown what specifically brought on the event, the current theory was a sudden shift in global climate brought on by a large Volcano eruption in present day Siberia.

While Planet Earth has made an impressive resurgence of life since the event, It's believed that it set evolution of life on earth back some 300 million years, but Life began recovery pretty quickly for a geological standpoint at least. It took only 5 million years for Woody Trees to reach pre-Extinction levels and less than 5 million years from that to the full return of corals and calcified sponges. The End-Permian Event also saw the downfall of insects as the dominant for of life and represents the largest known mass exctinction of insects ever and the rise of Vertebrates in their place (technically they began prior to the extinction event , but they survived much better than the dominant invertebrates culminating with the rise of the dinosaurs. By comparison, the whole of the existence of Homo Sapien species is a 11,000 year period.

So while a 1 million year period is too quick, it's not far off to a recovery from a green house gas mass extinction event. As is otfen said when discussing the Dinosaurs, Life finds a Way. Typically in Mass Extinction events, that which dies creates an opening for a small family group to explode in evolution diversity to fill the once taken niches. It could be that in this event, you would have a recovery that allows extremophiles (Life that exists in conditions that are extremely hostile to most forms of life) of some sort to give rise to new life in infinite possibilities. One of the first rules of biology is that there are no rules.

I think there is one direction you could pursue.

Climate cannot explain the seas being dead "except very deep". That sounds more like poison killing all the algae. This also matches the drop in oxygen level.

Now assume that the poison is lighter than water. It would then form a thin layer on the surface of the oceans. This would drastically cut down evaporation and make the world much drier. Low evaporation would also cut down on clouds and visible weather.

Heat transfer from oceans to air would also be cut down. And the layer might have different albedo from sea water. So you could probably avoid a green house Earth and get your desired level of polar ice (ice would still float over a thin layer). Additionally while the oceans would still absorb the heat and transfer some of it to the the air, the hot air only goes up. It will circulate back after it cools but it doesn't rain down like water does. So heat transfer from oceans to ground would be cut down even more.

With very little rain the continents would be wastelands with very little life. They could easily be drier than most deserts since deserts get some water from it condensing from the air during night. With air being drier overall that would be cut down.

The big problem with this is that it requires literally oceans worth of poison that persists for millennia. I do not see how that could happen naturally or even accidentally. One possible reason to do this is desperation. You world is already dying and this might work as climate engineering. The projected alternative might have been even worse. This would require that the poison was originally non-toxic but turned toxic after being exposed to environment longer than pre-release tests covered. Something like that might conceivably happen by accident.

• It's happened before, several times. Just replace 'poison' with 'ash cloud'. – Morris The Cat May 9 '19 at 14:37
• I have an idea to contribute to this one. Replace your 'poison' with an organism that produces a biofilm over water. en.wikipedia.org/wiki/Biofilm – Adam Miller May 9 '19 at 16:14
• @AdamMiller I thought about that but could not figure a way the bacteria producing the biofilm could survive when everything else dies. I mean it can't eat algae because we want that gone and it can't use photosynthesis because then the oxygen level won't drop... But you are right otherwise it would be really nice. – Ville Niemi May 9 '19 at 16:42
• @VilleNiemi it's likely impossible to kill off 'everything'. It'd be more practical to kill off higher life forms. Either way, there are methods of photosynthesis that don't produce Oxygen: en.wikipedia.org/wiki/Photosynthesis – Adam Miller May 9 '19 at 16:47
• The problem here is the million-year timeframe. Most poisons break down on a timescale of days to weeks. Even the really long-lived ones like arsenic or organomercury compounds only last centuries. After a million years, not only is the poison likely to decay, if it doesn't, something will evolve to eat it. – Mark May 9 '19 at 21:14

No

98% of all the landmass is wasteland/desert

Kinda hard when when ocean levels remain the same. Too much liquid water around.

There are only two climate zones, hot and dry around the equator and cold and dry on the poles Blockquote

Hot + dry = evaporation and evaporation means rain. If everything was either cold and dry or frozen and dry, that would work

The two poles are some big chunks of ice, each covering about 20% of Earth's area

Sounds like an ice age which means the oceans levels are not the same.

Ocean level is about same as today and still contain some life down really deep, but all the streams are dead

Life is a lot harder to kill than you might think. For life to only exist down deep, something must be continually killing everything that comes up too high

The atmosphere is still intact, but with more CO2 and not much O2 left

Co2 is a greenhouse gas so would increase temps

There are no animals (at least not so big that a human eye can see it) and no flora

Again life isn't that easy to kill. Something would have to continue killing it

There is no weather. Little to no wind, rain only arises and goes off over the ocean

Weather is related to temperature. The hotter the planet is, the more violent the weather can get. To have no weather, you need to freeze the planet.

Solution / possible cause

Look to Mars and why it is like it is.

Now to get to Mars like atmosphere, you need to stop Earth's iron core from spinning removing the magnetosphere that protects the planet from the solar winds. Bit hard as it would require getting rid of the moon.

Once the magnetosphere was gone, solar radiation would blast the surface killing everything not protected so all land life and shallow sea life would die (and stay dead). Life down deep could escape the radiation for a while but will eventually die too.

Solar winds would strip the lighter gasses from the atmosphere such as oxygen and leave heavier gases like CO2 behind.

The thinner atmosphere would trap less heat making it colder and reducing rainfall and weather events (but not removing them completely). This would produce cold deserts.

Terraforming would be difficult as would explaining away what happened to the moon.

Not sure one million years is long enough for all this to happen.

Most of the criteria you're describing can be met, but the mechanism you're thinking of isn't going to do it. Pollution and Global Warming aren't ever going to create the desert wasteland you're thinking of, but there's another solution.

if you want a desolate wasteland with no plants and no animals, you need to blot out the sun COMPLETELY for a good long while. There are two mechanisms that have done exactly this a few times in the past: Volcanoes and Impacts.

Either one will generate a condition where there is an enormous amount of ash particulate in the atmosphere. This will block out solar radiation and prevent light and heat from getting to the surface. No light means no plants, no plants means no animals. A sufficiently catastrophic event would wipe out pretty much all life except for the extremeophiles in the deep oceans who get all their nutrients from volcanic vents.

Have a good long read of the wikipedia page on extinction events. Either a Flood Basalt event or a sufficiently large (e.g. dinosaur killer) impact would generate most of the conditions you're describing.

• Have a good long read of the articles linked from that page. Neither a flood basalt event nor an asteroid impact is severe enough to have the desired effect. Even the Permian-Triassic event (the "Great Dying") only hit 70% of terrestrial species. – Mark May 9 '19 at 21:11

I think you have a stilted version of what our CO2-induced climate change is actually doing. In a super short time we've shot up from about 200PPM to 400 (and still going straight up). In the Jurassic and Triassic, it bobbled around 2-3 thousand. During the Cambrian is was typically more like 4.5 thousand.

Average temperatures in those eras were much warmer too, but what that meant for the planet was the water cycle was running much faster. So it was rainyer, not drier.

Now realize that what plants live on is water and CO2. So this situation, while bad for a lot of the animals (particularly large specialized animals), is heaven for most plant life (and by extension, the animals living off those plants).

As the great George Carlin said, we shouldn't be egotistical about this. The Planet will do just fine. Its the people who won't do so great. That's including a lot of other large animals though, of course. As Carlin said, the Earth will shake us off like a bad case of fleas.

• More CO2 might well benefit plants, but it will lead directly to a warmer climate (and indirectly to drier conditions, damaged proteins, lower concentration of nitrogen, looser soil, more erosion, stronger winds, fewer insects for pollination...) which might be very bad for plants. "Heaven for most plant life", hardly. Some plants might do well. Others might do well if they have time to evolve to the changing environment. Vast numbers of other plants would die. More CO2 isn't enough of a positive to overcome the negatives. – BittermanAndy May 9 '19 at 17:30
• @BittermanAndy - A warmer global climate by definition is a wetter one, as heat is what drives the water cycle. At least until it gets so hot that all water evaporates, I suppose... – T.E.D. May 9 '19 at 18:30
• @BittermanAndy, the problem we're encountering with "more CO2" isn't the amount of CO2, it's the rate of change. Give the planet a million years to adapt to the new conditions, and life will do just fine. – Mark May 9 '19 at 21:05
• @T.E.D. ...but the soil dries out quicker when the rain has passed, and dry soil erodes more easily, so next time it rains, the water just runs off rather than soaking into topsoil that isn't there any more. You end up with rainy deserts, not forests. – BittermanAndy May 10 '19 at 9:50
• @Mark sure, I even mentioned "time to evolve" in my comment. You're right (up to a point; not many plants on Venus), but a species can't evolve if the changes happen in less than one lifetime for that species (or in only one or two generations). From the point of view of that species, "too much CO2" and "too much CO2 in a short space of time because it'll take several generations to evolve to meet the new environmental conditions and there isn't enough time for that because the CO2 is rising too quickly" are the same thing. – BittermanAndy May 10 '19 at 9:56

Almost certainly not. But you might be able to get close.

Posit a runaway greenhouse event. CO2 goes way up, oceans heat up, water gets in atmosphere, repeat and oceans boil, and it spirals upwards until the surface of the planet is well over boiling everywhere.

This might be triggered by a spike the sun's radiation output.

If the sun radiation output then falls, the runaway greenhouse would fail to continue, and the atmosphere would precipitate back out. But all life would have been sterilized off the surface of the planet; possibly some deep down life might survive.

It would cool, and microbiotic life would recolonize the surface from deep in the crust. But it would be little more than slime, and it might not even have green photosynthesis.

A purple ocean might result that emits far less O2 than green algae.

Humans would arrive on a planet with oceans, rivers, CO2 and low O2, and rain. But no life on land, and oceans full of purple bacteria.

You could even make the sun's energy flare be triggered by an attempt to "dampen" the sun to prevent a less runaway greenhouse effect that backfired. (Note that "dampening" the sun is a K1 to K2 civilization effort; but so is interstellar travel, so...)

Another possibility is that there are "humans" in the solar system that aren't biological.

1. The ozone layer disappears. This could be a result of human activity and perhaps what prompted their departure.

2. Without ozone all the UV light from the sun hits the surface of the Earth.

3. The surface is sterilized by UV.

4. Reduced carbon on the surface (plant remains etc) slowly oxidizes, consuming remaining O2 and producing CO2.

5. As CO2 levels rise the oceans become acidic from dissolved CO2, finishing off ocean life except that around deep hydrothermal vents.

6. Absent any remaining photosynthetic organisms there is no more oxygen being made and no hope of regenerating the ozone layer.

7. Without plant mediated transpiration on the surface, humidity falls. The bare earth absorbs most solar energy in tropical areas, leaving them hot and dry. The bare earth reflects most solar energy in temperate areas, leaving them cold and dry.

8. Water is the second most important greenhouse gas and as humidity decreases, temperatures fall despite the elevated CO2 level.

That is 6 out of 7. No weather is the hardest; specifically wind. I cannot think of a way to abolish wind. Especially with hot areas and cold areas and atmopshere and the sun.

• Still has vast oceans for water to evaporate from so humidity isn't going to be affected that much from the loss of plants. – Thorne May 10 '19 at 2:52
• You think the ozone layer disappearing would cause humans to leave? Leaving with a plan to return would be much harder then building underground shelters and weathering the storm – Garret Gang May 10 '19 at 15:05
• Your #1 doesn't work. Ultraviolet light striking the upper atmosphere produces ozone. If you've got an oxygen atmosphere and a source of ultraviolet, you've got an ozone layer. #5 and #6 don't work, either: there are plenty of ocean-dwelling life forms that are resistant to carbonic acid (most of the photosynthesizers, for instance), and 10 meters of water provides about the same UV protection as the ozone layer. – Mark May 12 '19 at 6:21
• @Mark, we had oxygen and a source of UV in the 70s and 80s. The problem was we were kicking out CFCs which catalyzed dissolution of the ozone layer faster than O2 and UV could regenerate it. As regards realistic prospects for sterilizing the ocean, I agree with you. I would not buy it if we were making policy. But for a fiction I thought it hung together well enough. – Willk May 12 '19 at 15:13
• @Willk, the problem in the 70s and 80s was that we were kicking out CFCs that were destroying ozone in the polar regions. In the tropics, the ozone layer can regenerate completely in under a week and conditions favor the formation of hydrogen chloride, which doesn't destroy ozone; in the poles, and especially the South Pole, the ozone layer doesn't re-form at all during the winter and only weakly during the summer, while conditions favor the formation of chlorine monoxide, which does destroy it. – Mark May 12 '19 at 17:52