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