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Greenhouse gas emission scenarios

This image in wikipedia shows that the temperature is going to increase 4.1-4.8 °C in 2100 if no policies are taken.

How much raise in temperature can be reached in later times?

Is there some limitation to temperature increase?

For example, as far as I know, it is considered that the amount of available fossil fuels in the Earth is limited. What will happen if humans burn all the resources they can find to produce more CO2?

What is the maximum damage level, the maximum warming that can be reached by the oxidation of carbon by humans?

To extrapolate the graph, the upper border of the pink red area is going to be like 9 °C in 2200, and bottom border is going to be like 1 °C. It gets its peak in 2080 and then goes down.

So, can I ask some questions about this, if you agree with this prediction?

  • About the upper border: how far up can it go? Can it go to values like 20, 50, 100, 200 °C?

  • About the bottom border: why does it go down? I guess because plants and algae (may) start to grow better (because of the warm climate and abundance of CO2 and they suck in all the CO2.

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  • $\begingroup$ I had in University a course with a MeteoFrance physicist that told us their supercomputer predicts 4ºC for 2100 if this continues as it is. It is really sad. They didn't calculate for 2200, just for 2100. I don't know if there is a model for 2200, but it would have no sense, as we are not going to burn fossil fuesl in s.XXII. The nuclear fusion project is advancing. Also in s.XXII there migth be advances in geoengineering to stop this madness. $\endgroup$
    – user28185
    Dec 27, 2022 at 12:18
  • $\begingroup$ As for a limitation, I have the opinion there is a limit, as Phanerozoic CO2 levels where higer but temperature inferences doesn't shot to elevated numbers. The reason in my opinion is there is a negative feedback. More CO2->More heat->More clouds->More Albedo->Less heat. Anyhow here the last talk are models and supercomputers. $\endgroup$
    – user28185
    Dec 27, 2022 at 12:18
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    $\begingroup$ The vertical axis on the linked graph shows CO2 emissions per year rather than temperature change, with temperature change as a sidebar comment. There are lots of things that can cause CO2 emissions to start to drop in the future, even with no change in policy. For example, WWIII, famine, population decline due to reduced birth rates, population decline due to some future super-COVID, and that's not a complete list. $\endgroup$ Dec 28, 2022 at 9:44

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I would love to flesh out a full answer on this but I am currently at work so for now I will give some other factoids that affect my answer. The graph provided seems to give a very optimistic view of the effect that current policies will have.

In short, no, I do not think there is a limit. There are so many factors that contribute to and impact climate change; it is insane. To name a few:

  • the increased temperatures that we are currently seeing are melting the permafrost and glaciers. These areas are natural carbon sinks and currently hold large quantities of CO2 and methane. As they melt they release the stored methane, which is far worse for the atmosphere and environment than CO2.
  • the oceans are a major carbon sink as phytoplankton, like trees, absorb CO2 and release oxygen. while many species of phytoplankton enjoy the increased water temperatures, they do not do as well with acidic waters. the increased acidity would subsequently kill off most phytoplankton
  • old growth trees are also major carbon sinks. unfortunately, many of these trees have been cut down and the remaining forests are catching fire. Fires release CO2 into the atmosphere and kill off the trees that would pull the most carbon. less trees = more carbon = increased temps = more fires = less trees
  • all of these factors directly impact the wildlife and the balances that make life possible on earth. without them, the balance is thrown and a domino effect occurs

I see mentions of cloud cover which would minimally help, however, the increased methane creates holes in the atmosphere. the effects of this would outweigh the effects of cloud cover.

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  • $\begingroup$ i think also higher temperature -> more water vapor -> higher temperature, because water vapor is also a greenhouse gas. right? $\endgroup$
    – qdinar
    Dec 30, 2022 at 12:47
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    $\begingroup$ "I do not think there is a limit" - temperature on venus is 464 °C $\endgroup$
    – qdinar
    Dec 30, 2022 at 12:51
  • $\begingroup$ btw as i undersood/supposed, methane be converted/oxidizes into co2 after some long time... $\endgroup$
    – qdinar
    Dec 30, 2022 at 12:56
  • $\begingroup$ even if not all species of algae like acid water, those which like, may grow much. btw i have seen in a film that some grass-like algae feel good in acid water... but they need ground... $\endgroup$
    – qdinar
    Dec 30, 2022 at 12:58
  • $\begingroup$ @qdinar the extreme limit would be the planet without an atmosphere $\endgroup$ Dec 30, 2022 at 15:58

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