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How does CO2 level above 400 cause release of methane from Siberia? There is no established direct link between CO2 atmospheric levels and release of methane.

davedx 7y ago
More CO2 = more warming. The polar regions are so far seeing the most extreme temperature increases: see e.g. https://static.skepticalscience.com/pics/ArcticTC1880-2010NCEP.png https://static.skepticalscience.com/pics/ArcticTC1880-2010NC... Higher arctic temperatures = permafrost melts, releasing trapped methane. e.g. https://www.nature.com/articles/d41586-019-01313-4 https://www.nature.com/articles/d41586-019-01313-4
- assblaster 7y ago
  So CO2 --> methane is an indirect link at best, and methane levels have been increasing linearly for the last thirty years. https://climatenexus.org/wp-content/uploads/2019/05/ch4_trend_all_gl.png https://climatenexus.org/wp-content/uploads/2019/05/ch4_tren... There is no magical CO2 level of 400 that suddenly causes methane to be released from permafrost.
  - brylie 7y ago
    You might be reading the post too literally. The 400 PPM is a target that is easy for humans to discuss. The general idea that increased atmospheric CO2 leads to accelerated methane releases due to thawing of arctic permafrost still holds true, and humans need to set CO2 targets to mitigate this issue.
    - assblaster 7y ago
      What's implied with a 400 CO2 level is that anything under that is fine, but above that level it triggers a calamitous increase increase methane and a so called runaway greenhouse effect. This is simply not accurate, especially because the clathrates can release methane far below 400ppm. The CO2 level should be far lower than 400... A level closer to 200ppm should be the target.
  - dTal 7y ago
    The fear is that there is indeed a critical threshold beyond which the release of methane will form a self-sustaining feedback loop - hence the "gun". Nobody knows for sure whether this can happen, or at what level, but it's a sufficiently terrifying possibility to warrant talking in terms of thresholds we should really try to avoid. 400 is just a nice round number. The next nice round number, 500, is quite nasty even without the clathrate gun (2-3 degrees of warming).
gmuslera 7y ago
Check the GISS Surface Temperature Maps (https://data.giss.nasa.gov/gistemp/maps/index_v3.html https://data.giss.nasa.gov/gistemp/maps/index_v3.html) how the temperature anomalies were distributed around the world in the months of this year. In the upper latitudes you always have big patches with 4+C over the average of 1951-1980, the anomalies are not so extreme in the rest of the world. And in those regions in particular have 2 possitive feedback loops, with less snow the land absorb more heat, and then the "unexpected" release of methane.
gwbas1c 7y ago
Good question. Because methane is trapped in ice, and it's believed that the ice will melt, releasing more methane.
- assblaster 7y ago
  Methane has a short half-life, and is a small fraction of atmospheric particles compared to the other gases, and when methane decomposes it turns into carbon dioxide and water which is a less potent green house gas. Even if you release all the methane stored in permafrost, that effect will be short lived on a geologic timescale.

davedx 7y ago

More CO2 = more warming. The polar regions are so far seeing the most extreme temperature increases: see e.g. https://static.skepticalscience.com/pics/ArcticTC1880-2010NCEP.png https://static.skepticalscience.com/pics/ArcticTC1880-2010NC... Higher arctic temperatures = permafrost melts, releasing trapped methane. e.g. https://www.nature.com/articles/d41586-019-01313-4 https://www.nature.com/articles/d41586-019-01313-4

assblaster 7y ago
So CO2 --> methane is an indirect link at best, and methane levels have been increasing linearly for the last thirty years. https://climatenexus.org/wp-content/uploads/2019/05/ch4_trend_all_gl.png https://climatenexus.org/wp-content/uploads/2019/05/ch4_tren... There is no magical CO2 level of 400 that suddenly causes methane to be released from permafrost.
- brylie 7y ago
  You might be reading the post too literally. The 400 PPM is a target that is easy for humans to discuss. The general idea that increased atmospheric CO2 leads to accelerated methane releases due to thawing of arctic permafrost still holds true, and humans need to set CO2 targets to mitigate this issue.
  - assblaster 7y ago
    What's implied with a 400 CO2 level is that anything under that is fine, but above that level it triggers a calamitous increase increase methane and a so called runaway greenhouse effect. This is simply not accurate, especially because the clathrates can release methane far below 400ppm. The CO2 level should be far lower than 400... A level closer to 200ppm should be the target.
- dTal 7y ago
  The fear is that there is indeed a critical threshold beyond which the release of methane will form a self-sustaining feedback loop - hence the "gun". Nobody knows for sure whether this can happen, or at what level, but it's a sufficiently terrifying possibility to warrant talking in terms of thresholds we should really try to avoid. 400 is just a nice round number. The next nice round number, 500, is quite nasty even without the clathrate gun (2-3 degrees of warming).

gmuslera 7y ago

Check the GISS Surface Temperature Maps (https://data.giss.nasa.gov/gistemp/maps/index_v3.html https://data.giss.nasa.gov/gistemp/maps/index_v3.html) how the temperature anomalies were distributed around the world in the months of this year. In the upper latitudes you always have big patches with 4+C over the average of 1951-1980, the anomalies are not so extreme in the rest of the world. And in those regions in particular have 2 possitive feedback loops, with less snow the land absorb more heat, and then the "unexpected" release of methane.

gwbas1c 7y ago

Good question. Because methane is trapped in ice, and it's believed that the ice will melt, releasing more methane.

assblaster 7y ago
Methane has a short half-life, and is a small fraction of atmospheric particles compared to the other gases, and when methane decomposes it turns into carbon dioxide and water which is a less potent green house gas. Even if you release all the methane stored in permafrost, that effect will be short lived on a geologic timescale.