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Before becoming too alarmed, one might want to read about the Holocene Climate Optimum (https://en.wikipedia.org/wiki/Holocene_climatic_optimum https://en.wikip

Before becoming too alarmed, one might want to read about the Holocene Climate Optimum (https://en.wikipedia.org/wiki/Holocene_climatic_optimum https://en.wikipedia.org/wiki/Holocene_climatic_optimum). Temperatures 8000 years ago were significantly higher than 200 years ago. Did the lucky people 8000 years ago just barely escape disastrous climate tipping points? Or maybe such tipping points aren't so likely...

adgjlsfhk1 4y ago
climate change matters a lot more when you have trillions of dollars of infrastructure. before cities exist, it doesn't matter if a river moves half a mile. once you build a city on that river, the river moving now costs hundreds of millions of dollars.
- radford-neal 4y ago
  Rivers courses change all the time regardless of climate change. But in any case, this has nothing to do with whether there are "tipping points".
jandrese 4y ago
A lot of people died 8000 years ago as well. Anybody who says that the Earth has been this hot before and survived is technically correct, but they should look at this map and consider the implications: https://www.usgs.gov/media/images/map-united-states-late-cretaceous-time https://www.usgs.gov/media/images/map-united-states-late-cre... This is not a minor inconvenience for some people if we do nothing. This is avoidable disaster that we are ignoring.
- radford-neal 4y ago
  The late cretaceous was a lot longer than 8000 years ago. Lots of people did die 8000 years ago (of course!). It was also the time when important agricultural plants were being domesticated and civilization was beginning - probably because the climate was nice, allowing that to happen, when it hadn't for the previous 200,000 years of Homo sapiens' history.
  - jandrese 4y ago
    We have already blown past the CO2 levels of the Holocene maximum, so looking back to it as a stopping point isn't helpful. The Cretaceous had CO2 levels around 1000ppm so we aren't there yet. We are currently at around 418ppm and rising about 2ppm per year (but that rate is increasing). If we don't change our ways soon this scenario becomes increasingly likely. Also, there is an alternate theory that Humans finally developed agriculture because the climate change had made their previous hunter-gatherer lifestyle untenable and they were forced to improvise. Many species of animal died out.
Archelaos 4y ago
> Before becoming too alarmed, one might want to read about the Holocene Climate Optimum People are alarmed because a) the compositions of today's atmosphere is much different from 8000 years ago. So very different feedback circle become relevant for the future dynamics of the weather/climate, and we have every reason to expect that no limiting feedback circle kicks in before it does not get a lot worse than today. b) we are already well beyond the Holocene Climate Optimum (see the "2016" marker in the diagram of the Wikipedia page) and the increase of temperature (the derivative of the curve) has no known equivalent in the current Cenozoic period of earth's history. > Did the lucky people 8000 years ago just barely escape disastrous climate tipping points? I would rather rephrase the question into: Why did climate stabilized in the Holocene the way it did? and thus avoid "tipping points", because tipping points are not directly observable. They are features of (complex) dynamic systems. It makes only sense to discuss actual tipping points in the context of models that describe those systems.
- radford-neal 4y ago
  "the compositions of today's atmosphere is much different from 8000 years ago. So very different feedback circle become relevant for the future dynamics of the weather/climate" The CO2 level is higher. But the usual "tipping point" dynamics (eg, melting of permafrost) involves just the change in temperature, unrelated to the cause of the warming. And when the "tipping point" is supposed to cause yet more warming because it leads to release of yet more CO2, starting from a higher CO2 level actually reduces the effect, because the warming effect of CO2 is proportional to the logarithm of the CO2 concentration (so releasing X amount of CO2 causes a smaller temperature rise if the CO2 concentration is high than if it is low). "we are already well beyond the Holocene Climate Optimum" From the Wikipedia page: "the 2021 IPCC report expressed medium confidence that temperatures in the last decade are higher than they were in the Mid-Holocene Warm Period". That doesn't sound like "already well beyond" is firmly established.
  - Archelaos 4y ago
    My sentence about "very different feedback circles" indeed does not accurately express my intent. I should have written: "We should expect a very different pattern of feedback circles becoming relevant for the future dynamics of the weather/climate as was important to stop the temperature rise 8000 years ago."

adgjlsfhk1 4y ago

climate change matters a lot more when you have trillions of dollars of infrastructure. before cities exist, it doesn't matter if a river moves half a mile. once you build a city on that river, the river moving now costs hundreds of millions of dollars.

radford-neal 4y ago
Rivers courses change all the time regardless of climate change. But in any case, this has nothing to do with whether there are "tipping points".

jandrese 4y ago

A lot of people died 8000 years ago as well. Anybody who says that the Earth has been this hot before and survived is technically correct, but they should look at this map and consider the implications: https://www.usgs.gov/media/images/map-united-states-late-cretaceous-time https://www.usgs.gov/media/images/map-united-states-late-cre... This is not a minor inconvenience for some people if we do nothing. This is avoidable disaster that we are ignoring.

radford-neal 4y ago
The late cretaceous was a lot longer than 8000 years ago. Lots of people did die 8000 years ago (of course!). It was also the time when important agricultural plants were being domesticated and civilization was beginning - probably because the climate was nice, allowing that to happen, when it hadn't for the previous 200,000 years of Homo sapiens' history.
- jandrese 4y ago
  We have already blown past the CO2 levels of the Holocene maximum, so looking back to it as a stopping point isn't helpful. The Cretaceous had CO2 levels around 1000ppm so we aren't there yet. We are currently at around 418ppm and rising about 2ppm per year (but that rate is increasing). If we don't change our ways soon this scenario becomes increasingly likely. Also, there is an alternate theory that Humans finally developed agriculture because the climate change had made their previous hunter-gatherer lifestyle untenable and they were forced to improvise. Many species of animal died out.

Archelaos 4y ago

> Before becoming too alarmed, one might want to read about the Holocene Climate Optimum People are alarmed because a) the compositions of today's atmosphere is much different from 8000 years ago. So very different feedback circle become relevant for the future dynamics of the weather/climate, and we have every reason to expect that no limiting feedback circle kicks in before it does not get a lot worse than today. b) we are already well beyond the Holocene Climate Optimum (see the "2016" marker in the diagram of the Wikipedia page) and the increase of temperature (the derivative of the curve) has no known equivalent in the current Cenozoic period of earth's history. > Did the lucky people 8000 years ago just barely escape disastrous climate tipping points? I would rather rephrase the question into: Why did climate stabilized in the Holocene the way it did? and thus avoid "tipping points", because tipping points are not directly observable. They are features of (complex) dynamic systems. It makes only sense to discuss actual tipping points in the context of models that describe those systems.

radford-neal 4y ago
"the compositions of today's atmosphere is much different from 8000 years ago. So very different feedback circle become relevant for the future dynamics of the weather/climate" The CO2 level is higher. But the usual "tipping point" dynamics (eg, melting of permafrost) involves just the change in temperature, unrelated to the cause of the warming. And when the "tipping point" is supposed to cause yet more warming because it leads to release of yet more CO2, starting from a higher CO2 level actually reduces the effect, because the warming effect of CO2 is proportional to the logarithm of the CO2 concentration (so releasing X amount of CO2 causes a smaller temperature rise if the CO2 concentration is high than if it is low). "we are already well beyond the Holocene Climate Optimum" From the Wikipedia page: "the 2021 IPCC report expressed medium confidence that temperatures in the last decade are higher than they were in the Mid-Holocene Warm Period". That doesn't sound like "already well beyond" is firmly established.
- Archelaos 4y ago
  My sentence about "very different feedback circles" indeed does not accurately express my intent. I should have written: "We should expect a very different pattern of feedback circles becoming relevant for the future dynamics of the weather/climate as was important to stop the temperature rise 8000 years ago."