Thank you Stephen- I've posted a very brief ( under 4 minute ) < a href ="https://www.youtube.com/watch?v=y-0RRDf8vAI";> slideshow illustrating some of these points:
https://www.youtube.com/watch?v=y-0RRDf8vAI</a> On Wednesday, April 26, 2017 at 4:12:28 PM UTC-4, Stephen Salter wrote: > > Hi all > > The change from an untreated cloud to a treated one is much smaller than > that from a cloud to clear sky let alone day to night. The contrast change > needed to offset double CO2 with 18% low cloud cover is well below the > detection threshold of a human eye. > > Stephen > > On 26/04/2017 17:40, Russell Seitz wrote: > > Andrew wrote On Sunday, April 23, 2017 at 9:40:00 PM UTC-4: > > I don't think hydrosols will behave like CNN, in terms of their radiative >> properties. As I understand it, CCN act to brighten existing cloud cover. >> They won't, therefore, work on cloudless days. Likely, relative efficacy >> will depend on whether acute or chronic thermal stress is most important. >> Furthermore, hydrosols will cause a lasting increase in diffuse radiation. >> In terrestrial models, this has impacted NPP. >> >> I'm no expert on this niche - but that's my initial thoughts. >> >> Hope it helps >> >> >> It will take field experiments and further modeling to quantify the Net > Photosynthetic Product impact of surface water brightening , but Andrew > should bear three things in mind > > 1. Backscattering light does not have the same effect as casting shade, > because most plankton and algae can absorb light in all directions, > > 2. Hydrosols scatter the infalling light in all directions, - they > change the geometry of the euphotic zone in a diffferent manner than > extensive cloud cover. > > 3. Doubling surface brightess at high sun angles , from ~ 7% to 14% > reduces the underwater light flux by about 7%, which while obviously > significant, is a small reduction relative to full cloud cover, which > often reduces surface light more than twice as much, as white clouds in > the air can have an albedo of up to .55.- m > > It may l accordingly take as much NPP research to sort out the > ecological meaning of the physically uncontroversial cloudy day analogy > as that of CCN shading of overheated seas , both triopical and > circumpolar. > > > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > To post to this group, send email to [email protected] > <javascript:>. > Visit this group at https://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/d/optout. > > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
