this post was submitted on 31 Jul 2023
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Weren't there periods in the past where temperatures were "a few degrees" higher and still had conditions that could sustain human life?
Here is a very good graph demonstrating the first part of the problem:
https://xkcd.com/1732/
The globe is warming faster than any animal can adapt. And it's going to keep warming, even on net zero emissions, because the carbon dioxide is already in the atmosphere.
The second part of the problem is that previous periods of warming did not involve the release of underground carbon reserves. That carbon has been there since the age of the dinosaurs. That carbon is going to CONTINUALLY warm the earth, it's not going to just stop warming up like a volcanic eruption. Not until it's recaptured and buried.
Also, the carbon dioxide is turning into carbonic acid in the oceans, and we haven't felt most of the effects of that because the calcium carbonate buffer has been protecting us. When the buffer runs out, we're going to see some very big changes very quickly.
According to graphs I have seen, this won't be the fastest warming period ever, even by worst predictions. Example: https://scitechdaily.com/images/Past-and-Future-Global-Temperature-Trends-scaled.jpg
The second problem I have with your post is that there were far higher CO2 levels in history which didn't correlate with temperature rises.
Also, a lot of this global extincion theories are just theories that are based on predictions that are dependant on inputs and not all inputs (not even close) are considered in those calculations. Even IPCC itself thinks not including clouds feedback (and it's dominant termostatis control of temperature) could be a potential problem in their predictions.
All in all - human extinction theory is not something there is a consensus for and it certainly is a part of alarmism.
However, scientists have conclusively demonstrated that in the 19th through 21st centuries, CO2 emissions directly predict rises in temperature.