[pnacze199204]

The layman's question. Is there a maximum temperature that can be reached by air on Earth due to global warming? For example, one that would prevent living organisms from functioning? I read somewhere that with the increase of the sun's brightness by 10%, the average temperature on our planet will be 47 C. This, however, only for about 600 million years. Would global warming enable reaching such a high average temperature? Thanks in advance for your answer!

[Enthalpy]

Global warming does not result from increased emission by the Sun, so those are distinct questions.

If the greenhouse effect remained as efficient as now (but it would worsen) then 10% more Sun power would increase Earth's average temperature by roughly 2.5% as the planet radiates as T⁴ more or less, so the mean temperature would rise from 288K=+15°C to 295K=+22°C, a 7K increase.

How hot could Earth become if the greenhouse effect goes badly wrong and no life absorbs the CO₂? I propose to scale it from Venus. Being 0.723 as distant to the Sun as Earth is, it receive 1.913* as much light power per surface unit and its surface temperature is 735K=+462°C. Just by scaling the received power, Earth with a greenhouse effect as bad would have 625K=+352°C mean surface temperature. This is an unjustified computation, but is there a better one?

Very few living organisms resist a bit over +100°C, supposedly only where a higher pressure keeps water liquid.

[magician4]

a different opinion:

Global warming does not result from increased emission by the Sun, so those are distinct questions.

first of all, we - as scientists - should take a closer look at the real situation at hand ref. "global warming": is there a global warming at all, and if so, is it unusual with respect to geological "records" ( to be more precise: reconstructions form numerous proxies) etc. ect.
hence, for starters, let's take a look at recent satelite data link to graph
(for a more detailled discussion, source of the graph see: link )

let's now go back like... sixty million years? (δ ¹⁸O-racio) : link to graph , from: link
... or, even more long-term: 600 million years temperature ./. CO₂-level reconstruction (source)

my reading:
  climate has always changed, and mostly more drastically than nowerdays ... and most likely will keep on doing so.
  we're in a pretty cold period right now, speaking longterm, and "enjoy" a small intermediate with not-so-icy climate, but still are like 10°C colder than at the times of the dinosaurs
  the sun became like 30% brighter over the past ~ 4,5 billion years whilst the rotation period of earth increased from like 8 hours to nowadays 24 hours (to understand the meaning of this, look at temperatures on moon's surface bright side/darke side)
... with rotation slowing down in the future 'till a day becomes like a month. this will happen, and it's pretty scary in it's own right

so, from a first glance it seems like emissions from the sun in fact don't have relevant influence on climate.
... or do they?
well, it seems like the very influence of the sun towards or climate doesn't come from total radiation ( which doesn't change drastically, hence is called a "solar constant"), but from the composition of named radiation: heavy particle radiation - named "solar wind" - is the name of the game, and this is something that changes drastically every now and then ("solar cycle" [from: link]) 

the first to put forward this hypothesis (as derived from long-term observations [link to source]) was Prof. Svensmark, hence it's called the "Svensmark-hypothesis"

...and it has recently been vindicated by CERNS cloud-project : yes, there IS a relevant connection between sun's activity and earth's climate, there is solid scientific evidence for this by now.
[and I find it most disturbing that the scientists involved were forbidden to explain the meaning of their findings with respect to climatechange, as those were felt to be "politically incorrect" (sic!): postfactual times / science, indeed]

  therefor, my best scientific opinion is, that we can't neglect the influence of the sun

If the greenhouse effect remained as efficient as now (but it would worsen) (..)

what type of "greenhouse effect" are you takling about? the "real" one, where hot, humid air is trapped under the roof of a glashouse ect. ...
... or the "so called one" [IPCC insists that every insulation caused by the athmosphere has to be called just so, from now on, thereby confusing scientific facts to the max] ?
with respect to my first type (the real greenhouse): there is no such thing in the athmosphere, as satelte data show (fig. ## 5 , 6 )

... and the second one should stay pretty much stable, as the composition with respect to relevant gases in earth's athmosphere isn't likely to change in the future: there will be ups and downs with respect to humidity in lower atmosphere, yes, and ups and downs with respect to cloud formation, yes, but that's about it
[if you think that the miniscule contribution of CO2 might have somthing to do with it: look at Lambert-Beer, look at band-saturation and so on... ]

  in my opinion, fact is that we didn't even begin to understand "climate" with respect to identifying all the relevant drivers, much less to quantify their influence in terms of some degrees celsius: everything else is pure guesswork, OR "computermodelling" (which could be an honourable approch, if the models were evaluated, but in reality isn't, as they aren't ... a sad fact in its own right)

(...) then 10% more Sun power would increase Earth's average temperature by roughly 2.5% as the planet radiates as T⁴ more or less, so the mean temperature would rise from 288K=+15°C to 295K=+22°C, a 7K increase.

in addition to my above remarks: this oversimplyfied approach contradicts like everything we know from historical records.

How hot could Earth become if the greenhouse effect goes badly wrong and no life absorbs the CO₂?

geez, did you ever take a look in history of life on earth? what climate we did have, let's say, at the times of the dinosaurs, where it was roughly speaking like 10°C hotter than today?
... and you think + 7°C is a global killer?
now, that's an real alarmist's conclusion, in my opinion

I propose to scale it from Venus. (...)

I don't
... or to be more specific: I totaly reject this absurd idea
(you can't compare a planet with a day longer than a year and surface air pressure of ~ 100 bar - mostly carbondioxide - to any future earth: this simply won't happen)
... and any linear scaling from this to a possible earth's future  with "352 °C" (sic!) is... beyond the pale for a scientist, to put it mildly.

This is an unjustified computation (...)

yes , it is, it's unjustified, unscientific, u name it

however, in times of postfactual and postmodern science, this even might result in some funding ...
... as the "assumptions" of nowadays computer modelling and their "climate projections" ( they don't call it "climate predicions" any more for a reason!) show.*⁾


regards

Ingo


*⁾
predictions from models have to be validated, no way around this.
those models can't be: they simply fail with any reasonable test, even with the input of "adjusted historical climate data" - as they call their fraud by now.
... and hence, with a slight change of wording ...
... now you can put into your model whatever floats you boat, even the most absurd rubbish, as long as new horror emerges from your data. its just projection, hence nothing serious, just playing around with parameters, isn't it?

[wildfyr]

The issue with climate change is not that the earth is going to get so hot life cannot exist, or even that humans cannot exist. The earth has indeed has higher CO2 content and temperatures during the periods life has existed. I agree that to destroy all life we would basically need to look like Venus (but some extremophile bacteria might disagree with me)

The flashing red light is the speed at which temperatures and CO₂ have spiked. Normally these levels of variations are over a thousand years or so. We have spiked in the last 100 years.

Look at these two graphs

source:
https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide


source: https://www.ncdc.noaa.gov/global-warming/last-1000-years

I'll point out that neither of these are projections or models, they are "live" data.

IF the Sun can affect our climate, shouldn't we be working to mitigate it by lowering the amount of IR absorbing gases we emit into the air? I also reject out of hand anything sourced from Infowars. I do not even feel the need to justify why.

I also always like to think about the problem this way: If we treat human derived global warming seriously and act to prevent it what is the worst outcome? A fractionally lower average GDP of each nation on earth? Perhaps even an economic crash on the level of 2008? Or 1929? Tough, but we recovered from those.

What is the worst case scenario for ignoring it? Sea rise buries coastal cities, famine as crops fail, more aggressive storm systems damage infrastructure, loss in biodiversity as animals cannot evolve or adapt quickly enough.

But screw me, those money grubbing 95% of climate scientists who agree human caused climate change is real are just lying and twisting data to get paid amiright? Its not like they are experts who spent decades of their life training to parse such data. The rest of us brilliant armchair climate scientists who spend 2 hours a month on it can see the real truth /s

[magician4]

The issue with climate change is not that the earth is going to get so hot life cannot exist, or even that humans cannot exist. The earth has indeed has higher CO2 content and temperatures during the periods life has existed. I agree that to destroy all life we would basically need to look like Venus (but some extremophile bacteria might disagree with me)

that's what "Enthalpy"'s posting was all about, and that's what i felt might need my different opinion

... and I am glad that you support my evaluation insofar

as for the rest of your valuable contribution: we now could open up a scientific discurse ad nauseam , as for most of your statement a lot of further aspects could be named - leading to totally different conclusions

do we really want to do this here?

regards

Ingo

[wildfyr]

No, we have addressed OP's question, and I am happy enough that you read my post.

[Enthalpy]

Magician4, you can't take data from 400M years ago when continents were not at their present positions, and deduce something about carbon dioxide no solar radiation.

After that blunder, don't make reproaches to any scientist.

[magician4]

Magician4, you can't take data from 400M years ago when continents were not at their present positions, and deduce something about carbon dioxide no solar radiation.

can't I ?
well, I can, and I did, and will keep on doing so
 ...at least as long as someone with a reputation will show up, and proof to the rest of the paleoclimatic community that this really is a blunder, i.e. that the position of continents, their shape etc. ect. really is a relevant game changer with respect to carbon dioxide/solar radiation , and that hence those historic data are meaningless - which didn't happen sofar, if memory serves

After that blunder, don't make reproaches to any scientist.

goin' straight ad hominem, hu?
thats what I like about those "activists": "never discuss subject , attack the man, repeat the mantra : dangerous manmade global warming is happening !"


have a nice day...


Ingo

[Borek]

Locked. This is going nowhere.