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Comment by leereeves | Hacker News Reader

There's a great deal of spin coming from the people warning about climate change too. End of the world stuff.

Here's something to consider: during the Early Eocene period (roughly 50 million years ago) temperatures were 9C-14C higher than now and CO2 levels were 1000-2000 parts per million [1].

And yet according to science, Earth was covered in forests from pole to pole, mammals flourished, and the oceans were "teeming with fish and other sea life". [2]

That's something you won't hear much about, because it doesn't fit the agenda.

1: https://www.ncdc.noaa.gov/global-warming/early-eocene-period

2: https://en.wikipedia.org/wiki/Eocene

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Spin? Doesn't seem like spin, more the best prediction on available data. Few sciences are perfect. Do we talk of spin from gravity science because we haven't yet proved that?

For the Eocene, also according to science, we see fossil evidence of crocodiles at the poles. That likely makes most of the temperate to equatorial zones uninhabitable for humans, whilst being lovely for the "snakes found in the tropics that would require much higher average temperatures to sustain them".

I notice you don't mention that "All the members of the new mammal orders were small, under 10 kg", and "Eocene mammals were only 60% of the size of the primitive Palaeocene mammals that preceded them. They were also smaller than the mammals that followed them".

So whilst it was lovely for species evolved to those conditions, and life as a whole, for large species such as those of the size of say humanity, it seems to have been exceptionally hostile.

> All the members of the new mammal orders were small, under 10 kg.

I don't know if that statement is technically true but it's certainly misleading. Perhaps "all the members of the new mammal orders" were under 10kg, but not all mammals during the early Eocene were under 10kg.

Cambaytherium and Coryphodon, for example, lived during the early Eocene and were roughly pig sized and cow sized, respectively.[1,2]

In other words, that carefully phrased statement, if true, is a great example of the unscientific spin I was talking about.

> fossil evidence of crocodiles at the poles. That likely makes most of the temperate to equatorial zones uninhabitable for humans

We also see fossil evidence of large mammals in India. In the early Eocene temperatures differed less between the tropics and the poles and between winter and summer.

1: https://www.thoughtco.com/coryphodon-peaked-tooth-1093184

2: https://en.wikipedia.org/wiki/Cambaytherium

> In other words, you seem to be suggesting that all the mammals that lived during that era were under 10kg, which would be a great example of the unscientific spin I was talking about.

I'm suggesting nothing of the kind, but directly quoting from the wikipedia page you linked. Please stop putting words in my mouth.

I will note that the Wiki page on Coryphodon says: "These changes in size are thought to be linked to global climate change, with the size minimum in the Coryphodon lineage occurring shortly after Paleocene-Eocene boundary". Which appears to indicate clear evolutionary pressure to evolve smaller.

The pressure on mammals appears to have been consistently toward smaller size, seen in newly evolved species and the evolution of existing species. We already know that heat penalises larger mammals harder than the small, so that does not seem inconsistent.

> for large species such as those of the size of say humanity, it seems to have been exceptionally hostile.

That was your statement, not Wikipedia. What was that based on if not the incorrect implication about the size of mammals?

Nonetheless, I've already edited my post to make it clear that I was talking about the implications of the statement from Wikipedia.

> The pressure on mammals appears to have been consistently toward smaller size

If "the size minimum in the Coryphodon lineage occurr[ed] shortly after Paleocene-Eocene boundary" then the decrease occurred before the early Eocene, not during. The temperature actually continued to increase for several million years after the Paleocene-Eocene boundary.[1]

That pressure might have been due to the rapid changes at the Paleocene–Eocene Thermal Maximum, not temperature itself, and after the thermal maximum, size increased again even with the higher temperatures.

1: https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Therm...

If there's evolutionary pressure on existing species to become smaller, and newly evolved species are smaller than those of preceding and following eras, it seems entirely reasonable to conclude it was somehow hostile for larger land mammals, no? That is not a statement that every single one was under 10kg or perfectly fit the identified trend.

We should remember that even during the adjacent times (the Paleocene and Middle Eocene) temperatures were about 8C higher than they are now, and large mammals (some of the largest ever) evolved during those times.

The decrease in size probably had more to do with the chaos wrought by whatever unknown event caused the thermal maximum than with the temperature itself.

To make this all more relevant: I'm not saying that climate change won't be disruptive. It will. I'm just saying we can adapt and endure. And I think we should plan for that, because we clearly aren't going to stop it.

It is interesting that with climate change, the public debate is mostly about 'is it man-made?' as if it'd just become a non-issue if it was. It's debating a fundamental point while we need practical solutions or even just concepts to cope with all sorts of interconnected problems on the entire spectrum of what we as humans are able to address - from microorganisms to geopolitics. While at this point, nobody is sure what will happen, societies will get a clearer picture of the imminent consequences over the next decades. At the moment, everyone seems to be waiting.

You might have disproved the point that all mammals very less than 10 Kg, but Wikipedia states on the Coryphodon[0] that the size of the species also decreased, and that "these changes in size are thought to be linked to global climate change". So the general argument certainly seems to hold.

It also "had one of the smallest brain/body ratios of any mammal, living or extinct" so that may not be the best example of how this kind of environment might be fit for humans.

[0]https://en.wikipedia.org/wiki/Coryphodon

Most people warning about climate change don’t say it is the end of the world, they say climate is complex, we never did this before, nature will be fine, but if whether human civilisagion will be fine is not very sure.

It is a huge experiment on a planetary scale and staying on the safe side here is simple the rational approach.

The irrational approach is to hope it will somehow turn out great, despite the already grim looking damage predictions.

And the simply evil approach is working against scientific evidence and rational arguments for personal gain. People like these are like cancer, destroying civilization from within for personal growth.

You forgot those who you would call evil + rational. These people willingly rather take their chances in Max Max world than give something up now.

Sure, but those changes took millions of years and evolution had time to work. Making similar changes over decades does not give evolution time to adapt.

> temperatures were 9C-14C higher

In such an environment, mankind might survive, but our current farming set-up won't. It might only kill 7 billion people our of 7.5, no big deal. (When looked at from a few million years in the future.)

> CO2 levels were 1000-2000

Indoor CO2 levels are usually double the outdoor levels. H Humans become dumb/sluggish at concentrations over 1500ppm, and nauseous at over 2000. Life will thrive, human life won't.

On the scale of millions of years, Earth's life will adapt to the new, extremely warm climate we are causing to occur.

On the scale of centuries, in this extremely rapid warming event we are making happen, a majority of life on Earth will die, including most humans. Evolution is slow, global warming is fast.

In the very long run, yes, palm trees (or their evolutionary successors) will flourish in Antarctica.

In the short run, meaning a length of time that exceeds human written history, we will live in an inhospitable ecological desert, and billions will die.

That's something YOU won't hear about, because it doesn't fit the agenda of the people that are lying to you for profit.

I think a major concern is that lots of us might be part of the mass extinction event that will happen during the transition period.

What about all the people living in coastal areas or close to major rivers? That’s like 50% of the population, in addition to much of our shared history (buildings). It will all be under water and cause large migrations, unsettling much of society. Is that not worth fighting for?

it is a weird western media quirk that the first symptom people talk about is sea level rise. I think its an accidental product of all the news reports about melting ice caps and polar bears, so people have scoped the problem as ice melting and water rising in their heads.

this is basically, to a first order approximation, wrong. sea level rise, even in a nasty BAU/RCP8.5 scenario is really a next-century problem. we're talking tens of centimeters.

meanwhile, vast swaths of the euphrates, indo-gangetic, nile and yellow river deltas will suffer droughts and both successive and concurrent crop failures.

the flood of refugees from drought/famine/war into every city around the world will vastly exceed the flood of water at their shoreline (this century).

You're right, I didn't even mention the droughts and famines. I'm Dutch though so perhaps I'm slightly biased or preoccupied :/

IPCC are projecting 26cm-98cm rise by 2100. So it's more tell the grandkids to build inland a bit.

Wouldn't the transition from life that thrives at 200 to 500 ppm to life that thrives at 1000 - 2000ppm suck though?

I thought the big deal was that we liked it how it was.

It is. But environmental narratives fed to people are confused; they're mixing up "protect the nature because it's cute" with "protect the nature because our food depends on it".

I don't know about you but I think 14C hotter sounds pretty unpleasant

that's on average, too. extremes would be, uh, extreme - 50-60C?

At 1000 ppm of CO2 human cognition starts to decline. At 2000 ppm you're looking at severe cognitive decline, drowsiness, headaches. Letting it get that high is dangerous just on the basis of CO2 concentration alone.

I am all for controlling CO2 and moving away from fossil fuels but I also agree with you.

Climate is complicated, there are many complicated feedback loops going on. As just one example warming temperatures promotes plant growth especially algae which captures CO2 interning back to the ocean floor. Of course some of that algae is not good for us (red tide).

I am not worried about life on earth, it will adapt and survive, it has seen worse, I doubt we would turn into Venus, but its a slight possibility.

The issue is what happens to human society, it will most likely adapt too, but at what cost? Rising sea levels, food supply having to adapt, these things could caused great suffering to many, then again maybe not. I don't want my kids to suffer or their kids.

The point is we don't exactly know how it will play out so why push it? Lets get off fossil fuels as fast as we can, we know its the right thing to do for many reasons, one of which is to stop returning so much CO2 back into the atmosphere.

But how long did the transition to those conditions take? We're changing the climate so fast that there is no chance for anything to evolve with the change.

True, but nowadays we can't afford geographically changing human-inhabitable areas driven by climate change.

If climate change causes the areas we currently inhabit to become unhospitable, we risk adding the danger of economic disasters and wars threatening our survival.

Human life was, amongst other things, possible because of one of the biggest climate disasters ever to occur on earth, the big oxygenation event [0], so we could even see climate change as something positive but clearly that doesn't buy us anything today.

0: https://en.wikipedia.org/wiki/Great_Oxygenation_Event

"Agenda"? Good grief.

Sure, life will find a way. But the high rate of change will be disruptive.

Here's something to consider: The transition won't be pleasant.

I can assure you that you don't want to live in an atmosphere with 1000-2000 ppm CO2. Would you?

Don't forget that we are talking not only about climate change but also the rate of change. It's probably fine to have crocodiles at the poles if you have millions of years to adapt. If you only have a few decades it might not be so great.

I agree the panic seems a bit overdone sometimes. Also projecting current trends in renewable energy prices and storage we should be able to go zero net emissions in a couple of decades or so.

I really really wish that we are overdoing it. The data just looks that bad, and we are one the worst path.

We emitted 5/6th of what's ok to stay below 1.5°C, and 2°C is not that much more, and we're not stopping. (500 Gt vs 600 Gt)

At the current emission rate (12 Gt/yr) we have 10 years left to stop completely. A few decades won't cut it.

Almost all scenarious of the IPCC now include negative emissions to be able to reach the targets.

The technology does not exist, would need to be implemented on a massive scale (eg plant all the available area minus agriculture and a selected few sanctuaries with trees and make biochar out of them) and the investment in eg artificial photosynthesis is not there, probably because there is little money in it. (The process is different from that for biofuels.) We might not make it in time. Don't rely on this.

(The total available stored carbon seems to be on the order of 3000 Gt.)

https://www.ipcc.ch/report/ar5/wg1/summary-for-policymakers/ (Figure SPM.10)

I'm pretty sure there was also no one around to complain when their coastal cities filled with millions of people went under water. Pretty terrible example if you ask me.

What’s your point, exactly? It’s ok to wreck human civilization because the planet will eventually be covered in forests?

A reasonable person would call such a world and it's 500 trillion dollars hit to the economy 'unpalletable'

So overall you feel we don't need to take any measures to reduce our impact on the system?

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