Our climate projections for 2500 show an Earth that is alien to humans

[Nevilledog]

Link to tweet

https://theconversation.com/our-climate-projections-for-2500-show-an-earth-that-is-alien-to-humans-167744

There are many reports based on scientific research that talk about the long-term impacts of climate change — such as rising levels of greenhouse gases, temperatures and sea levels — by the year 2100. The Paris Agreement, for example, requires us to limit warming to under 2.0 degrees Celsius above pre-industrial levels by the end of the century.

Every few years since 1990, we have evaluated our progress through the Intergovernmental Panel on Climate Change’s (IPCC) scientific assessment reports and related special reports. IPCC reports assess existing research to show us where we are and what we need to do before 2100 to meet our goals, and what could happen if we don’t.

The recently published United Nations assessment of Nationally Determined Contributions (NDCs) warns that current promises from governments set us up for a very dangerous 2.7 degrees Celsius warming by 2100: this means unprecedented fires, storms, droughts, floods and heat, and profound land and aquatic ecosystem change.

While some climate projections do look past 2100, these longer-term projections aren’t being factored into mainstream climate adaptation and environmental decision-making today. This is surprising because people born now will only be in their 70s by 2100. What will the world look like for their children and grandchildren?

*snip*

[Klaralven]

1. If the population peaks at 10 B in 2100, then we have 400 years back to the 1700 level of 650 M

The growth in population from 1700 to 2100 is the direct result of cheaply extracted coal, iron ore, oil and natural gas.

With the cheap sources all gone by 2100, the population is likely to fall as fast as it rose.

[qazplm135]

2. 400 year climate projections are silly

I believe there is a climate crisis. I think billions could die if we don't work to address it.

But to make a projection that far is nonsensical.

Let's say the worst case is right. Well, in 100 years you probably have a few billion less humans to start. Which means you have a lot less negative impact on the climate. We'd probably be knocked back to pre-industrial time.

You telling me 300 years at that level won't even begin to revert things? I find that hard to believe.

[Spider Jerusalem]

3. If the worst case is right then humans will be extinct in a few hundred years (n/t)

[qazplm135]

5. no we won't

a global ice age couldn't kill us off.

Lots and lots of people will die in a scenario, civilization could certainly be threatened.

But humans are the most adaptable species on the planet. We will survive most things including worst case climate change.

[Spider Jerusalem]

6. Atmospheric CO2 is higher than it's been at any time in the last 20 million years

the last time the atmosphere was anything at all like this humans did not exist, at all, nor did any of our immediate ancestors. This is not a global ice age, it's much worse (we're looking at something more in line with the end-Permian extinction).

[qazplm135]

7. unless the temperature EVERYWHERE

is going to be uninhabitable, and it won't, then no humans won't go extinct.

They will migrate to where it's livable, and the polar regions will be as will some other areas.Alaska, Canada, Russia, Southern S. America even Antartica will become places humans can survive.

Humans exist right now, even with CO2 higher than before humans existed so that's not really an argument.

[Spider Jerusalem]

8. It isn't JUST about the temperature?

It's about ocean acidification and the collapse of the food chain. There are a vast number of consequences of climate change that make human survival in any worst-case scenario highly unlikely.

[qazplm135]

11. all life on earth ain't dying

sorry but it isn't. We eat anything, so we will adapt to eat whatever survives.

Hyperbole isn't going to convince anyone. Our side engages in apocalyptic hyperbole about everything, democracy, climate, and it doesn't convince the folks that need to be convinced, it just turns them off.

Why isn't billions will die enough?

[Spider Jerusalem]

13. Why on earth do you assume humans will survive?

Again: do you actually know anything at all about the effects of climate change? Do you know anything about previous mass extinction events, and why they happened? (Helpful hint: it was CO2 and methane release from the Siberian traps that led to the end-Permian extinction).

[qazplm135]

15. because we are one of the most adaptable species

this planet has EVER seen. If it kills us off, it kills pretty much everything off. We can eat only plants, we can eat almost any animal, we can modify our environment to make it more survivable.

[Spider Jerusalem]

16. That's so much nonsense

modifying our environment is what got us into the situation we're in with climate change in the first place; I don't know why you think we'll be able to engineer our way to survival when it's our intelligence and adaptability that've made a mess of things in the first place?

[qazplm135]

17. ok

you win, everyone dies. Might as well live it up then, it's all over.

[muriel_volestrangler]

25. You're mistaking survival for "engineering our way to survival"

It's not that we're bound to have a civilization; it's that humans, with our ability to eat almost anything, use fire, build boats, communicate, and plan, can find niches almost anywhere on Earth, and have been able to do all that for tens of thousands of years, predating civilization.

[Spider Jerusalem]

26. I am not particularly optimistic about our collective chances of survival

considering that we're looking at something very similar to the conditions that caused the Permian extinction playing out over the next few centuries or so.

[muriel_volestrangler]

27. The difference is that humans can plan to adapt to changes in their environment

whereas other animals can't, and couldn't in previous mass extinctions. And we are also 'generalists' that can get food from a wide range of sources, so we're not reliant on a few particular species surviving with us.

The highest Permian CO2 level in the paper your article links to was over 6000 ppm. Human populations may well crash, but that will mean fewer of us putting out CO2, so to get to "very similar" conditions is not really possible.

[Spider Jerusalem]

28. Are you aware of how much methane is trapped in permafrost and on the seafloor?

The release of all that methane is going to boost atmospheric CO2 concentrations very considerably. Will it get to 6000ppm? Unknown, but there's a reason that climate scientists talk about feedback loops and tipping points; a mass release of methane is one of those tipping points.

[muriel_volestrangler]

29. Yes, but no-one knows if that will be a tipping point or not

or how quick it will be. It doesn't make the survival of the human species "nonsense".

[Buckeye_Democrat]

4. I agree.

It reminds me of a manager from Japan boasting to all of us employees that our Japanese-owned company had a 300-year business plan, whereas most American companies were lucky if they had a 10-year plan.

I sat there quietly thinking, "How could you possibly account for technological and societal changes over 300 years?! That boast actually makes the company seem insane."

[NickB79]

9. Climate change is a freight train. Once started, it takes a long time to stop

Right now, we're well over 400ppm of CO2 in the atmosphere.

The last time we had this much CO2 was almost 3 million years ago. Sea levels were over 50 FEET higher. There were alligators in Minnesota and forests at the poles.

Even if we stopped all carbon emissions now, it would take 100,000 yr for nature to sequester the carbon we've emitted. And that assumes we haven't yet kicked off positive feedback mechanisms like permafrost thaw or a rainforest wildfire death spiral that will cause CO2 levels to keep rising further on their own. And we can't even hope that nature will adapt like it did in previous, natural warming phases, because we're heating the planet at a rate faster than it's seen in 60 million years.

Barring some revolutionary carbon sequestration deus ex machina or vast geoengineering schemes, sea levels will rise tens of feet in 400 yr. All coastal cities will be lost. Most polar ice will be lost. Most rainforests and almost all coral reefs will be wiped out, ushering in a mass extinction we haven't seen in 65 million yrs.

[qazplm135]

12. well then there's no point right?

You're argument is it's already too late, everyone's dead, they just don't know it yet.

So why would folks do anything about it with that argument?

[NickB79]

23. There's always a point in trying

While I fear that we've already unleashed a mass extinction event, I share your optimism that at least a few populations of humanity can come through the other side, after this thing we currently call civilization collapses. However, the more carbon we emit now, the dimmer that chance becomes. The longer we can hold off collapse, the greater the odds we can establish lifeboats of humanity IMO.

Who knows, maybe we can even genetically engineer our descendants to survive more effectively in the new world we're creating.

[qazplm135]

24. I think the most likely outcome

is that people die in poorer countries, we lose some coastlines, we have some food shortages, and then we finally collectively realize it's a problem and make changes.

It's not going to be a mass worldwide extinction of everything.

We aren't going back to the stone age.

But we are going to see massive loss of life and problems, and really, that's bad enough.

[Elessar Zappa]

14. We can still stop a worst case scenario.

All hope is not lost.

[jimfields33]

18. So your saying 50 million years ago we were in the same situation

without human behavior like fossil fuels? Hmmmm. How on earth did it get so bad back then? And weirdly even if it was, the earth survived. Weird.

[NickB79]

21. No, I didn't say that at all, but thanks for playing

Note where I said we're warming at a faster pace than we've seen in 60 million years?

https://www.scientificamerican.com/article/todays-climate-change-proves-much-faster-than-changes-in-past-65-million-years/

The climate is changing at a pace that's far faster than anything seen in 65 million years, a report out of Stanford University says.

The amount of global temperature increase and the short time over which it's occurred create a change in velocity that outstrips previous periods of warming or cooling, the scientists said in research published in today's Science.

If global temperatures rise 1.5 degrees Celsius over the next century, the rate will be about 10 times faster than what's been seen before, said Christopher Field, one of the scientists on the study. Keeping the temperature increase that small will require aggressive mitigation, he said.

65 million years ago was when an asteroid took out the dinosaurs, killed 75% of all species on the planet, and caused a nuclear winter effect. Nothing bigger than 20 lb survived.

[marie999]

10. Since the world as a whole will not do anything significant to slow down climate change

it will get worse a lot quicker. In a way it might be a good thing in that people won't suffer as long. The worse the climate change the more people will die until we reach a point where the planet will begin to renew itself. And knowing how humans are it won't take them too long to not care about protecting the planet.

[jimfields33]

19. I thought shutting down the entire world in 2020 would do something.

It didn’t help a bit.

[JanMichael]

20. The Earth will be fine don't worry.

Remember during the covid shutdowns you can see the clear blue sky in Los Angeles you could see dolphins in the canals in Venice and so on and so on.

That only took a couple of weeks.

After things get really bad and food supplies go to s*** and water gets bad and populations are moved from the equator towards the North and the South to survive...

Once a smaller number of humans are basically beaten into living more holistically with the planet then environment will be nice and clear.

[roamer65]

22. Humans will be mostly gone by 2100.

[ZonkerHarris]

30. We had a good run.