At 11:29 AM 3/23/5, Stephen A. Lawrence wrote: >Horace Heffner wrote: > >> Research on runaway global warming, due to >> >>methane release and high altitude water vapor, is undervalued due to a type >>2 error. Failing to asses the risk early enough has a catastrophically >>high negative value. The probability of this risk is not zero, as >>evidenced by the climate mode of Venus. >> >> >Think positively! > >I think we can safely discount the Venus scenario.
There is stron evidence we can not safely discount the Venus scenario (see below.) >After all, Earth has >been through at least one apparently permanent "snowball" phase in which >the albedo went 'way up. My understanding is that the recovery path >from "snowball Earth" was provided by the accumulation of massive >quantities of CO2, released by volcanoes over a period of millenia, >which remained in the atmosphere, unused, due to the lack of green >plants. The CO2 level finally got high enough (10%? 20%?) to produce a >truly ferocious greenhouse effect, which eventually melted the snowball >... and as the albedo dropped, there must have been massive overshoot >since all that CO2 would have taken a very long time to break down, >leading to a very hot Earth for some period of time. The come-back scenario I read was based in part on volcanic ash deposited on the ice ball reducing the albedo. > >If that "hot Earth" phase wasn't enough to cook the CO2 out of the >carbonate rocks, which is the path which leads to a "Venus Earth", then >it seems very unlikely that industrial CO2, even combined with arctic >methane, could do it. That scenario did not produce sufficient high altitude water vapor. High altitude water vapor is the ultimate killer, not CO2 or methane. Increased concentrations of CO2 and methane warm things up enough to get the water vapor into the stratisphere, but it is the water vapor that causes the runaway. There is a gigantic supply of water. It is just a matter of tipping the concentration balance. We currently dump a lot of water vapor directly into the stratisphere via jet engine. A large methane release will directly increase upper atmospheric water vapor via the gradual oxidation of the methane. Methane is lighter than air. > >And if the carbonate rocks don't break down then I think we can also >safely assume that, in no more than a million years or so, global >warming will abate and the coral reefs can start to come back. The Venus runaway greenhouse effect was not initially caused by CO2, but rather high altitude water vapor, which has a very powerful greenhouse effect. Try googleing: venus greenhouse water vapor Especially check out from that result: <http:www.sciencedaily.com/releases/2002/05/020516080752.htm> <http://www.astronomynotes.com/solarsys/s9.htm> There is an area over the Pacific already in a *measurable* runaway regime. Melting of the polar ice caps and vast methane releases already underway may be enough to tip the balance to a clearly measurable global runaway regime. In my book, that means that we are currently in a runaway regime, a regime in which global warming will runaway unless drastic action is taken. This is not the definition of "runaway greenhouse effect" used in the second URL above, but it is a definition that makes more sense to me. If the progression will not stop without drastic intervention, then to me that is "runaway". Any other definition only clouds the issue. I was very happy to see all that information online. It was not available when I posted on the subject in 1998. Regards, Horace Heffner
