Pliocene and Eocene provide best analogs for near-future climates | Hacker News Reader

Pliocene and Eocene provide best analogs for near-future climates

pnas.org

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> Both the emergence of geologically novel climates and the rapid reversion to Eocene-like climates may be outside the range of evolutionary adaptive capacity.

A lovely little sentence, elegantly understated and used as a seemingly off-handed conclusion to the abstract, which essentially means "the world may be about to end."

Also, NASA is hosting the full article: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201800...

What is the range of evolutionary adaptive capacity, though? Life has survived everything that has been thrown at it in several billion years. We just don't know what it would take to wipe it all. So I don't think the authors were talking about the complete end of life. They were just saying that we're going towards a phase of mass extinction, and that is not much controversial.

> we are effectively rewinding the climate clock by approximately 50 My, reversing a multimillion year cooling trend in less than two centuries.

It’s the unprecedented suddenness of this climate change that makes it doubtful organisms will be able to adapt. Maybe we shouldn’t be concerned with whether or not some form of life will still exist, but whether or not we will.

It's time to start building domes.

Not domes so much as greenhouses. The climate change doesn't kill you, it kills the crops you depend on to live and then you starve.

Agreed; I think Sundrop Farms provides a path forward here.

http://www.sundropfarms.com/

Some other greenhouse examples that are decently large scale, although they don't necessarily use seawater or generate their own electricity.

https://bchothouse.com

http://inspiredgreens.ca

In case it's of interest to anyone, the more general (and extreme) concept would be vertical farming.

https://en.wikipedia.org/wiki/Vertical_farming

Traveler 4320, you are off-mission. Abort!

> It’s the unprecedented suddenness of this climate change that makes it doubtful organisms will be able to adapt.

Another wildcard is how much damage humans may inflict on ecological systems in a desperate search for food, when crop yields decline.

When crop yields decline, food will become scarce. I think the consequences of food scarcity will be social unrest and political chaos. People will turn against each other much before they turn against the environment.

> I think the consequences of food scarcity will be social unrest and political chaos.

I also expect increased overfishing and slash & burn agriculture: https://en.wikipedia.org/wiki/Slash-and-burn#Ecological_impl...

Life has indeed survived, but do we want to risk another Permian scale mass extinction? We don't know the limits, but we're currently experimenting with them. In other words we don't yet know the size of the push required to trigger that scale of extinction. Once we find out for certain it's almost certainly too late to avoid it.

For civilisation, humanity and most food chains that would effectively be the end of the world even if it did not include extinction of homo sapiens.

"Once we find out for certain it's almost certainly too late to avoid it."

I don't understand why is that. What I do understand is that somehow, for so many like you, change is too often pictured as a bad thing. And I am glad that on the large scale we are inclined to be skeptical in our nature. And if some change happen to have something undesirable, I won't rush to blame the change, I would rather take a look at what change brought, good and bad, and only do something about the bad. So far, observing the general attitude, most of us seem to think like me.

Humans can (and will) get through climatic change events well enough. Even if today we could have only 20% of our current arable land, that would be enough to feed more than our current population level, providing that the necessary diet adjustments are made (e.g. less beef). The past mass extinctions could not be mitigated by coordinated reactive actions that are possible today and it's simply wrong to attempt to project something similar with equal level of destruction into our future. We have the power to preserve almost everything we deem worth preserving and we do exactly that. Actually, if nothing else, thanks to us, the life on our planet has the highest chance of survival in the future "mass extinction events".

It's quite simple. Once a tipping point is passed, and clearly apparent, it's too late to stop it. We're not doing anything about the bad. It's right there in our system's designed-in premise that the bad is an "externality". There is far too much evidence to no longer believe in anthropogenic climate change, or that the change is not bad.

Nothing wrong with change per se. Nothing at all wrong with discoveries and inventions that have brought modern levels of health and comfort if we mitigate the costs. Everything wrong with change that makes our planet less able to support biodiversity, or to be slightly more emotive, an unpleasant, marginal, place to be for everyone. Change and develop without triggering the next great collapse. I do not want my comfort to be at the expense of every future generation.

Thankfully, at least in Europe, there are signs that critical mass of public opinion is being reached and there are increasingly strident calls to do something substantive. That's at odds with the general state of political opinion which seems to be trailing public opinion markedly.

> Humans can (and will) get through climatic change events well enough

Based upon what? This appears to be nothing more than wishful thinking or presumption.

https://www.theguardian.com/science/2019/jan/06/katharine-ha...

> We have the power to preserve almost everything we deem worth preserving

Which appears to be nothing unless it is profitable.

https://en.wikipedia.org/wiki/Holocene_extinction

That humanity could survive is moot if it involves going through a millennia long dark age, or effectively bombing ourselves back to the iron age.

> thanks to us, the life on our planet has the highest chance of survival in the future

Again, our track record speaks loudly against this.

"Based upon what? This appears to be nothing more than wishful thinking or presumption."

Based on many things. Our tenacity, for starters. Primitive as we were, tens of thousands of years ago we already had the capacity to populate almost the entire planet, be it the lush grasslands, or arctic/sandy deserts. Now count in our current capacity. Even in the unlikely event where we "bomb ourselves" into a nuclear winter, I very much doubt we'll suffer any long term major drawback. As the time progressed we simply became more proactive and prepared ourselves for such eventuality and have bounce-back plans in place. We have technical capacity to do a lot of things here on earth, including to direct the current climate change or even to arrest it if necessary. We just had no serious reason to do that. Overall, we are mostly at "seeking our comfort" stage, not on "straightening it up" stage. If the upcoming global warming will prove to be bad in almost all its aspects, that will warrant a change in our priorities; I have no doubts about it. But as I've tried to say, maybe the coming change isn't necessarily bad. Why won't we welcome it and experience it up close? What if the current increase in planetary temperature can be used somehow in our advantage? That, I reckon, is (or should be) our defining trait as evolving civilization.

"the life on our planet has the highest chance of survival in the future" "Again, our track record speaks loudly against this"

That is because you are inclined to listen that voice and ignore anything else contradicting it. We have reservations and other means where as time progressed, unlike the other extinction events, we took responsible steps towards preserving the existing species even in the face of their natural decline (arguably, examples of this may include Kakapo parrots or Panda bears).

I'm not very concerned about life. Some bacteria will surely survive almost any event and given a few billion years and a little luck biodiversity will probably be restored. I'm a lot more concerned about our current technological society.

The Earth doesn't have a few billion years. Multicellular life on Earth will end in about 800 million years.

https://en.wikipedia.org/wiki/Future_of_Earth

Ah, life will survive. No worries then. I'm sure civilization will sleep easy tonight knowing that cockroaches will still be around in a million years.

It is absolutely nowhere near evolutionary adaptive capacity. Life will not end and the world will still be there.

Life's evolutionary adaptive capacity is stagerring! Just take a look at the experiment where it barely stretches muscles: https://www.youtube.com/watch?v=plVk4NVIUh8

What I understand they mean is "Life as we know it" defined as large animals and familiar plants roughly in places where we are used to seeing them. We are looking at life with our antropocentric point of view and we basically want familiar stuff to stay the same and we don't want unfamiliar stuff to show up. We don't want things to change and that's why potential large shift in how life presents itself may be caulled as "end of the world" event, but it is not.

Life doesn't care whether oceans are clean or polluted, hot or cold. It WILL adapt some way or another even if all crustaceans and fish will die because they can't adapt quickly enough to lowering pH.

We should care not because life is at danger but because we are at danger. Life as we know it is a machine that supports us, let's us grow food and provides air and water and soil and climate that we need. Humans will survive for sure in one way or another even if the temperature rises by 20 degrees but what kind of life will it be and how much suffering for those that can't deal with it?

Pliocene like climates by 2040 is easy for me to swallow, after all the climates then seem similar to modern climates just warmer. Eocene like climates by 2050 is a bit harder to swallow. It's hard to imagine there being a tropical environment in the Arctic that can support alligators and Tortoises in about 30 years time.

Going from Pliocene to Eocene climates in as little as 10 years time makes me think the model either assumed a huge increase in greenhouse gas production with India and China becoming superpowers or assumed a runaway greenhouse effect.

It could just be due to exponential changes being hard to reason about, tipping points and all that.

Skimming the paper, it looks like they predict pliocene/eocene climates primarily for equatorial zones, with polar and high-latitude regions less effected. Eocene climates were also more even, with less of a difference between polar and equatorial temperatures. So alligators in the arctic is not strictly being predicted (at least not on that timescale, and that's not to say the predictions aren't scary in plenty of other ways.)

> The Mid-Pliocene becomes the best climate analog slightly sooner, by 2030 CE, but the prevalence of Eocene-like climates accelerates after 2050CE, and future climates most commonly resemble the Eocene by 2140 CE

Changes towards Eocene accelerates by 2050 according to the models & doesn't reflect Eocene until 2140 CE. Still the rate of change is incomprehensible IMO.

For anyone interested in finding out more about the last 50-60 million years of climate history I would strongly recommend this talk: https://www.youtube.com/watch?v=Yze1YAz_LYM

I think we passed the tipping point for the climate 25 years ago, we just didn’t know it, or even today full grasp it.

I was saying 10 years ago they by 2024-2028 we would see runaway climate changes.

I have friends and relatives that are climate related research scientists. 10, 5, and 3 years ago they thought I was crazy, last year they have all expressed concerns that I might have underestimated the speed of change. They are very scared.

I hope I’m wrong, but I don’t think I am.

Depends what you mean by 'runaway climate change'. It takes some time for climate to stabilize, even if we stopped all carbon emission now it would take a few decades for the planet to reach equilibrium. We've certainly reached the point where significant impacts are going to be felt but not necessarily to the point where, say, the Earth loses all polar ice and remains hot for tens of thousands of years.

> I was saying 10 years ago they by 2024-2028 we would see runaway climate changes.

> 10, 5, and 3 years ago they thought I was crazy, last year they have all expressed concerns that I might have underestimated the speed of change.

It's important to recognise that neither you nor I have the expertise to truly assess this. The climate models are the best we have but there are various uncertainties. I'm also concerned that they may turn out to be too conservative but it will take many years to find out.

The most optimistic scenario is that the models break in our favour, serious action is taken, technology bails us out somewhat and investment in low-carbon energy and sustainable farming provides employment. The worst case scenario is that crop yields and fisheries collapse well before the end of the century.

Which of our major food-crops can handle Pliocene and Eocene climates?

None. Obviously this is suggesting mass human die-off or total extinction.

Famine -> law and order breakdown -> mass migrations -> wars and military conflicts -> population reductions.

Hmmm. I have read this in human history before.

Complicated question - it's called climate change for a reason. Unfortunately I found it difficult to turn up easy to read climate maps for different historical periods, but I did manage to find a couple.

First our baseline - check out this very detailed present day biome map.[1]

For an idea of what things probably looked like during the Pliocene, check out this biome map.[2] Note that a portion of the central US (our bread basket, so to speak) was desert. But then, also notice that a large swath of Texas was actually grassland and that temperate forest extended down to approximately LA.

As for the Eocene, things actually look pretty good in the US crop wise. From figure 6 of this paper [3], it looks like the west coast was warm temperate forest while almost the entire rest of the US was tropical forest.

That being said, don't get the wrong idea. Just because you can still grow crops doesn't mean you can grow the same crops, or in the same places; things will probably not be going so well. In a best case scenario climate change still presumably causes massive disruptions to our societies as well as large scale economic damage simply by rapidly changing things.

[1] https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/use/w...

[2] https://en.wikipedia.org/wiki/Pliocene_climate#/media/File:P...

[3] https://www.geosci-model-dev.net/7/2077/2014/gmd-7-2077-2014...

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