Hi Ken, and others, I agree that it's good to work with a range, to cater for uncertainties, in order to come up with worst-case and best-case scenarios. To facilitate this, it's good to hear about any concerns about safety, risks, unintended consequences, etc. In that spirit, I'll add some myself.
Ever since I floated ideas of spraying water vapor into the sky, people have been writing me with concerns, such as that - hydrogen and oxygen will escape from Earth into space; - some areas will receive salty rains and decrease in fertility; - the greenhouse effect of water vapor is too strong, more heat will be trapped than light will be reflected back into space; - decrease in light will reduce growth of vegetation, crop, etc. Similar concerns apply to suggestions to the suggestion to burn more coal, crop residue, wood and dung (the idea being that less sunlight will then penetrate Earth). Another concern with this idea is that this will - apart from the CO2 emissions - add large amounts of soot into the atmosphere, which appears to be underestimated in regard to its impact. In an article I wrote last April (URL below), I quoted a study by Professor V. Ramanathan and G. Carmichael of UC San Diego, concluding that black carbon causes a warming effect in the atmosphere of about 0.9 watts per meter squared. That compares to earlier estimates of between 0.3 watts per meter squared of the Intergovernmental Panel on Climate Change (IPCC). Black carbon could have as much as 60% of the current global warming effect of carbon dioxide (CO2), i.e. more than that of any greenhouse gas besides CO2. http://www.gather.com/viewArticle.jsp?articleId=281474977306586 One problem is that soot and dust particles can rise high into the atmosphere, keeping heat trapped underneath. Furthermore, soot and dust particles can cover ice and snow on mountaintops, causing an albedo change that will accelerate the melting of glaciers, which are crucial in that they feed rivers that supply water to crop, livestock, people and vegetation. The fear is that, once the glaciers have melted, the rivers will stop flowing, causing droughts that will bring famine and endanger the lives of vast amounts of people. In that respect, water vapor is much more benign; it can result in more snow in the mountains, with positive contributions to glaciers and rivers, while the light surface of snow and ice will reflect more sunlight back into space. Cheers! Sam Carana On Wed, Dec 24, 2008 at 1:48 PM, Ken Caldeira <[email protected]> wrote: > Andrew, > > Perhaps instead of trying to rank technologies, which involves coming up > with a scalar value for a multivariate phenomenon amid uncertainty, it would > be more useful to list the characteristics of each approach that someone > could use to do a ranking. > > This would be especially useful if uncertainty ranges could be specified > instead off simple numbers, and there were suggestions on how uncertainties > might be diminished. > > Best, > > Ken > > PS. It would be interesting to try to get some specificity on claims of > environmental risk. For example, is there anybody who really believes there > is significant direct risk associated with the fertilization activity > proposed by Climos? If the real concern is the slippery slope and not the > possible effects of the proposed activity itself, it would be useful for > that to be out in the open. If people really do think there could be lasting > bad effects from their proposed activity, it would be useful for someone to > try to provide evidence of this risk. > > ___________________________________________________ > Ken Caldeira > > Carnegie Institution Dept of Global Ecology > 260 Panama Street, Stanford, CA 94305 USA > > [email protected]; [email protected] > http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab > +1 650 704 7212; fax: +1 650 462 5968 --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
