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NSF, quite a piece of revelation you've got there. Blew my mind, it did. Do you think it's maybe because them scientists haven't figured that out? Maybe they don't know. You think? I think you should go tell them. Take your three graphs with you and show them how it's done. Show them your hard data! Poor lost souls! They dwell in ignorance without you! They have nothing better than the media to get their information from. Go! Save them! Why are you wasting your time on this blog!? Go!
Toggle Commented Sep 16, 2013 on Pinpointing the minimum at Arctic Sea Ice
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@Tor Thanks for the correction. It looks like I missed that one.
Here is a link to Hansen's paper. I'm not sure how close it is to the version to be published in "Philosophical Transactions," but the summary in the Guardian fits... somewhat. I'm not an expert on this topic, so some of the finer points might have gone over my head, but I don't think that the main point of the paper is to discuss the Venus effect, which he clearly states is not likely; not for a few billion years when the sun gets a lot brighter than today. He also dismisses the possibility that a mid-range runaway greenhouse effect, a.k.a "moist greenhouse," is possible. "Similarly, a Venus-like baked-crust CO2 hothouse is far distant because it cannot occur until the ocean escapes to space. We calculate an escape time of order 10^8-10^9 years even with the increased stratospheric water vapor and temperature at 16×CO2. Given the transient nature of a fossil fuel CO2 injection, the continuing forcing needed to achieve a terminal Venus-like baked-crust CO2 hothouse must wait until the Sun's brightness has increased on the billion year time scale." (p. 17 - in the link) Rather, the point of the paper is to get a more accurate estimate of climate sensitivity (he lost me here on a few things), with special consideration to how it may vary across climatic states. Based on those estimates, and making a series of assumptions about CO2 levels, Hansen does say that a "low-end greenhouse effect," which, as far as we are concerned, would render the planet mostly uninhabitable. "On the other hand, conceivable levels of human-made climate forcing could yield the low-end runaway greenhouse. A forcing of 12-16 W/m2, which would require CO2 increase by a factor of 8-16 times, if the forcing were due only to CO2 change, would raise global mean temperature by 16-24°C with much larger polar warming. Surely that would melt all the ice on the planet, and likely thaw methane hydrates and scorch carbon from global peat deposits and tropical forests. This forcing would not produce the extreme Venus-like baked-crust greenhouse state, which cannot be reached until the ocean is lost to space. Warming of 16-24°C produces a moderately moist greenhouse, with water vapor increasing to about 1% of the atmosphere's mass, thus increasing the rate of hydrogen escape to space. However, if the forcing is by fossil fuel CO2 the weathering process would remove the excess atmospheric CO2 on a time scale of 104-105 years, well before the ocean is significantly depleted. (p. 24; my emphasis) What is interesting (if I understood his point correctly) is that, within the model's parameters, it is not necessary to burn all remaining fossil fuels to get a low-end runaway greenhouse effect.
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