This is how deniers argue - latch onto trivial language in the title, and spew doubt. Instead of trying to understand, which would probably scare the pants off of them. So they put blinders on instead.
This is how extremists argue - spew the most outrageous ideas they can get away with, and when they cross the line into obvious lies, they attack the other side for "latching onto trivial language."
The editorialization is patently false. You are wasting political capital by defending it.
Well... extremely difficult, since all known climate evidence directly contradicts your proposition. 420ppm is not super great, but to call it "unprecedented" takes a mind-blowing quantum of scientific illiteracy.
No need to project your hysterical fears unto others. Your unfounded claims have been thoroughly debunked by skepticalscience.com [1] [2], together with all the other arguments [3].
Literally nothing you posted supports your argument that 420ppm is unprecedented. Again, perhaps you should focus more on scientific accuracy and less on outrage and flamewar, or perhaps go to a different website.
400+ ppm is unprecedented since 800 000 years, and the effects are recognizable now by year-by-year changes that consistently break out of historical limits for both temperature and CO2 concentrations:
That effects of CO2 concentrations are different now than hundred million years ago is covered in this link that was provided (please see how solar forcing have increased over millions of years, lowering greenhouse gas thresholds): https://skepticalscience.com/co2-higher-in-past.htm
I see no reason to make false accusations and trying to bring the argument down to an emotional level. I suggest reading the links and debunking, and instead try to understand the scientific arguments first.
This post of yours reflect an arrogance that do not belong on HN (my response was to show you what you projected from yourself - this, since facts only enrage some people):
"May I suggest adopting a mental model where you care about accuracy more than outrage?"
Instead, may I suggest you provide real arguments, instead of unsubstantiated nay-saying, and avoid resorting to pure rhetorical tactics? I say this because you provided nothing of value to the discussion. Instead even your own link supports current model precisions, contradicting your own claims:
"There is good agreement between model simulations incorporating high CO2 concentrations and proxy evidence, providing strong support for the role of CO2 in maintaining the high temperatures of the Early Eocene."
Sorry for bringing out more of the same, but that was the emotional part of the argument. But shouldn't really be necessary to show, regardless wether we agree or disagree about data and models.
I present what experts in the field are saying (the references are more accurate, yes). Please see other posts in this parent thread for more nuances. Would love for real contradictory arguments to be presented!
Where are the credible peer-reviewed research that present contrary findings?
At this point, contrary views seems to boil down to: Putting the lid on a pressure-cooker will not lead to chaotic disturbances and rising energy imbalance inside the pot. While thousands of peer-reviewed papers all point in the same general direction. They credibly even raise concerns that above certain thresholds, hot house earth as shown by data from ancient times, may happen again and may happen faster/more robustly than expected.
I doubt facts are going to change minds, but it should be concerning that we're already witnessing all the signs after rising CO2 and warming since 1930's:
It is of course going to take a few more years for real devastation to occur, but the present condition is in-line with simpler models from 70's and 80's. It is just now that we're breaking out from historical envelope, so it is from this point onwards the effects turn more chaotic.
But of course, laymen and hobbyist working unrelated to climate fields know better.. Especially when fueled by money and special interests (billionaires). They somehow always manage to find any incredible argument for explaining away the effects of massive amounts of extra fossile mass having been released over the past hundred year.
Of course CO2 doesn't work alone, but triggers more greenhouse effects (H2O, methane, albedo, etc.) due to a new imbalance in the system compared to historical times of stable civilization and climate.
If we were hunter-gatherers, we would've not needed to be as concerned. But we're not, and not being hunter-gatherers we might just have a chance to avoid a possible "Great Filter" of our times.
There is a huge difference between "humans affect the climate" and "we are all going to die within a couple of years because of human's effects on the climate".
Unprecedented? When the dinosaurs evolved, there was 5-6 times as much CO2 in the atmosphere as today, thanks to millions of years of volcanic activity.
"Another important factor is the sun. During the Ordovician, it would have been several percent dimmer according to established nuclear models of main sequence stars. Surprisingly, this raises the CO2 threshold for glaciation to a staggering 3000 ppmv or so. This also explains (along with the logarithmic forcing effect of CO2) why a runaway greenhouse didn't occur: with a dimmer sun, high CO2 is necessary to stop the Earth freezing over."
Civilization is dependent on the observed equalization of planetary energy input-output present for the past 10 000 years, along with stable CO2 levels. Both temperature and CO2 concentrations are breaking out of that envelope since 1930's, thus challenging poweful one-way threshold effects that will further release yet more greenhouse gases. Just this time without human intervention. It's kind of like lighting the fuse of a gigantic environmental bomb.