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In a world with such high climate sensitivity, is there still a realistic pathway to an acceptable outcome? SSP1 2.6 was already highly optimistic and with thes

In a world with such high climate sensitivity, is there still a realistic pathway to an acceptable outcome? SSP1 2.6 was already highly optimistic and with these two new models even it doesn't keep us below 2 degrees.

trevyn 7y ago
Perhaps it’s time to start considering how to choose to live given unacceptable outcomes.
- consumer451 7y ago
  > Perhaps it’s time to start considering how to choose to live given unacceptable outcomes. Maybe I am misunderstanding your statement, but to which period of time are you referring to? Your lifetime? 3 generations? The long now includes a non-zero probability of a collapse of atmospheric oxygen, and complete human extinction within ~3600 years. [0] [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5138252/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5138252/
  - AbrahamParangi 7y ago
    I may be misunderstanding it but that paper reads as completely ridiculous. We haven’t had a hypoxic atmosphere in the history of the earth since the evolution of photosynthesis (that’s a 2 Billion Year track record). The support for the plausibility of the author's hypothesis is that if you fit a parabola to the data over a certain time window, you get 100% decrease in atmospheric oxygen in a few thousand years?? That model is just nuts. By the same token it predicts we will have negative oxygen shortly thereafter.
    - consumer451 7y ago
      I would love to have someone convince me that this paper is utter rubbish, so I really appreciate your comment. I am also likely a bit annoying as I don't have a science background. However, you said: > We haven’t had a hypoxic atmosphere in the history of the earth since the evolution of photosynthesis (that’s a 2 Billion Year track record). This research seems to disagree, doesn't it? [0] > Climate change triggered by volcanic greenhouse gases is hypothesized to have caused the largest mass extinction in Earth’s history at the end of the Permian Period (~252 million years ago). Geochemical evidence provides strong support for rapid global warming and accompanying ocean oxygen (O2) loss, but a quantitative link among climate, species’ traits, and extinction is lacking. To test whether warming and O2 loss can mechanistically account for the marine mass extinction, we combined climate model simulations with an established ecophysiological framework to predict the biogeographic patterns and severity of extinction. Those predictions were confirmed by a spatially explicit analysis of the marine fossil record. [0] https://science.sciencemag.org/content/362/6419/eaat1327 https://science.sciencemag.org/content/362/6419/eaat1327
      - AbrahamParangi 7y ago
        See [0] for atmospheric oxygen levels over time. That dip from ~35% to ~15% atmospheric oxygen corresponds approximately to the permian extinction (~250 mya). My understanding is that there have been a number of oceanic hypoxic/anoxic events[1] in the history of the planet but that atmospheric oxygen levels have been relatively high since the oxygen holocaust[2]. [0]https://www.pnas.org/content/pnas/96/20/10955/F2.large.jpg https://www.pnas.org/content/pnas/96/20/10955/F2.large.jpg [1]https://en.wikipedia.org/wiki/Anoxic_event#Anoxic_events_in_Earth's_history https://en.wikipedia.org/wiki/Anoxic_event#Anoxic_events_in_... [2]https://en.wikipedia.org/wiki/Great_Oxidation_Event https://en.wikipedia.org/wiki/Great_Oxidation_Event
      - gus_massa 7y ago
        In the first article, fitting that data with a parabola+trigonometric is a very big red flag. The error interval for the quadratic coefficient must be huge, but I can't find it. It may be fit with a line+trigonometric to get some approximation for the next few years (10? 100?). With a line you get 50000 years to the 0 oxygen level, that is less alarmist than 3600 years. Also, without a good model it's a bad idea to extend these projections too much. There are a lot of natural process that depend on the concentration of oxygen and will change. For example, under 15%-10% concentration of oxygen you can't burn wood so you solve the problem of forest fires https://en.wikipedia.org/wiki/Limiting_oxygen_concentration https://en.wikipedia.org/wiki/Limiting_oxygen_concentration

trevyn 7y ago

Perhaps it’s time to start considering how to choose to live given unacceptable outcomes.

consumer451 7y ago
> Perhaps it’s time to start considering how to choose to live given unacceptable outcomes. Maybe I am misunderstanding your statement, but to which period of time are you referring to? Your lifetime? 3 generations? The long now includes a non-zero probability of a collapse of atmospheric oxygen, and complete human extinction within ~3600 years. [0] [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5138252/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5138252/
- AbrahamParangi 7y ago
  I may be misunderstanding it but that paper reads as completely ridiculous. We haven’t had a hypoxic atmosphere in the history of the earth since the evolution of photosynthesis (that’s a 2 Billion Year track record). The support for the plausibility of the author's hypothesis is that if you fit a parabola to the data over a certain time window, you get 100% decrease in atmospheric oxygen in a few thousand years?? That model is just nuts. By the same token it predicts we will have negative oxygen shortly thereafter.
  - consumer451 7y ago
    I would love to have someone convince me that this paper is utter rubbish, so I really appreciate your comment. I am also likely a bit annoying as I don't have a science background. However, you said: > We haven’t had a hypoxic atmosphere in the history of the earth since the evolution of photosynthesis (that’s a 2 Billion Year track record). This research seems to disagree, doesn't it? [0] > Climate change triggered by volcanic greenhouse gases is hypothesized to have caused the largest mass extinction in Earth’s history at the end of the Permian Period (~252 million years ago). Geochemical evidence provides strong support for rapid global warming and accompanying ocean oxygen (O2) loss, but a quantitative link among climate, species’ traits, and extinction is lacking. To test whether warming and O2 loss can mechanistically account for the marine mass extinction, we combined climate model simulations with an established ecophysiological framework to predict the biogeographic patterns and severity of extinction. Those predictions were confirmed by a spatially explicit analysis of the marine fossil record. [0] https://science.sciencemag.org/content/362/6419/eaat1327 https://science.sciencemag.org/content/362/6419/eaat1327
    - AbrahamParangi 7y ago
      See [0] for atmospheric oxygen levels over time. That dip from ~35% to ~15% atmospheric oxygen corresponds approximately to the permian extinction (~250 mya). My understanding is that there have been a number of oceanic hypoxic/anoxic events[1] in the history of the planet but that atmospheric oxygen levels have been relatively high since the oxygen holocaust[2]. [0]https://www.pnas.org/content/pnas/96/20/10955/F2.large.jpg https://www.pnas.org/content/pnas/96/20/10955/F2.large.jpg [1]https://en.wikipedia.org/wiki/Anoxic_event#Anoxic_events_in_Earth's_history https://en.wikipedia.org/wiki/Anoxic_event#Anoxic_events_in_... [2]https://en.wikipedia.org/wiki/Great_Oxidation_Event https://en.wikipedia.org/wiki/Great_Oxidation_Event
    - gus_massa 7y ago
      In the first article, fitting that data with a parabola+trigonometric is a very big red flag. The error interval for the quadratic coefficient must be huge, but I can't find it. It may be fit with a line+trigonometric to get some approximation for the next few years (10? 100?). With a line you get 50000 years to the 0 oxygen level, that is less alarmist than 3600 years. Also, without a good model it's a bad idea to extend these projections too much. There are a lot of natural process that depend on the concentration of oxygen and will change. For example, under 15%-10% concentration of oxygen you can't burn wood so you solve the problem of forest fires https://en.wikipedia.org/wiki/Limiting_oxygen_concentration https://en.wikipedia.org/wiki/Limiting_oxygen_concentration