I would expect the effects on circulation to matter. Cooling the atmosphere in some locations and heating it in others is basically what drives the whole circulation; changing that pattern of heating and cooling would affect the pattern of circulation. Since the effects we care about are mostly mediated by circulation, I find this type of idea more interesting for its potential to alter the details of climate than for its potential to affect global average surface temperature.
On Dec 23 2008, 1:39 am, "Ken Caldeira" <[email protected]> wrote: > The simulation I did that was reported on the article about Ron Ace was one > in a series of simulations designed to look at how various idealized energy > transformations affect climate. > > Because land cover changes change many things at once, it is illustrative to > look at idealized cases in which only one thing changes at a time. > > Also, there is extensive literature on land use change and its effects on > climate. > > http://www.google.com/search?q=land+use+change+climate > > ___________________________________________________ > 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 > > On Mon, Dec 22, 2008 at 1:09 PM, Andrew Lockley > <[email protected]>wrote: > > > > > Doesn't tree-planting achieve a similar effect by constantly sucking > > up groundwater and turning it into water vapour through transpiration? > > You have to set that against the dark vegetation colour, of course. > > Can someone with access to a climate model work out whether this is a > > viable alternative? One would assume that trees don't work as well > > but there would be more of them. As there used to be a far greater > > area of forest globally than there is today, would this simply be > > 'geoengineering things back to normal'? > > > Is this idea essentially the same as the sea-water spraying boats - it > > sounds it? > > > A > > > 2008/12/22 Alvia Gaskill <[email protected]>: > > >http://news.yahoo.com/s/mcclatchy/20081221/sc_mcclatchy/3126430 > > > > Water vapor's effects on atmosphere are debated > > > > By Greg Gordon, McClatchy Newspapers Greg Gordon, Mcclatchy Newspapers > > > 1 hr 14 mins ago > > > > WASHINGTON — Ron Ace's idea to cool the planet by evaporating water could > > > provoke controversy because it collides head-on with a concern of > > > environmental scientists: that water vapor is a potent greenhouse gas. > > > > A recent Texas A&M University study, based on satellite data from the > > > National Aeronautics and Space Administration , warned that if water > > vapor > > > levels in the atmosphere continue to rise, it "could guarantee" an > > increase > > > of several degrees Celsius in the Earth's temperatures over the next > > > century. > > > > These scientists warned of potential "positive feedback," in which water > > > vapor traps heat near the surface, the warmer temperatures cause > > increasing > > > ocean surface water to evaporate, producing even more water vapor, > > further > > > heightening the trapping effect and beginning the cycle anew. > > > > Kenneth Caldeira , a climate scientist for the Carnegie Institution's > > > Department of Global Ecology at Stanford University whose computer > > > simulation of Ace's invention suggests it would significantly cool the > > > planet, said that scientists are still trying to sort out the complicated > > > role of water vapor. > > > > Among its mixed effects: > > > > — It absorbs latent heat near the earth's surface and transports it to > > > higher altitudes, for a cooling effect. > > > > — When it condenses at higher altitudes, it releases the latent heat, > > which > > > then can radiate into space, producing more cooling. > > > > — It's a greenhouse gas, trapping heat and causing warming. > > > > — It can form low clouds that reflect solar energy, a cooling effect. > > > > — It can form more high clouds, which block some sunlight but mostly > > prevent > > > the release of infrared radiation from below, another warming effect. > > > > Robert Park , a retired University of Maryland physics professor, said > > > scientists are right to worry that water vapor and other greenhouse gases > > > could lead to thermal runaway — a cycle where two or more factors feed > > off > > > another to propel temperatures higher — but that no one has proved that > > it's > > > occurring because the atmosphere is so complex. > > > > "This is what makes climate such a horrendously difficult thing to > > calculate > > > . . . by far the most difficult calculation that man has ever attempted," > > > Park said. > > > > Ace hopes that his global cooling invention will help settle the matter. > > > > ----- Original Message ----- > > > From: Ken Caldeira > > > To: [email protected] ; [email protected] > > > Cc: [email protected] ; [email protected] ; > > > [email protected] ; George Ban-Weiss > > > Sent: Saturday, December 20, 2008 12:08 PM > > > Subject: [geo] Re: Ace Inventor Thinks He Can Rain in Global Warming > > > Steve et al., > > > > I have performed some climate model simulations of this idea (holding off > > on > > > assessing its engineering feasibility). > > > > Let us recall that evaporating water has several possible effects, some > > of > > > which are: > > > > 1. It cools locally by transport latent heat away from the surface > > > > 2. It warms somewhere else in the atmosphere by release of latent heat > > > during condensation. > > > > 3. If that latent heat condenses higher in the atmosphere, energy has > > been > > > transported upward, where it might more easily radiate to space. > > > > 4. It can diminish the vertical lapse rate (because a moister atmosphere > > > cools less with increasing altitude), so for a constant radiating > > > temperature at the tropopause the surface temperature would warm > > > > 5. Water vapor is a greenhouse gas and so an increase would contribute to > > > warming > > > > 6. Increased water vapor could form more low clouds, with cooling effects > > > because of high albedo > > > > 7. Increased water vapor could form more high clouds, with warming > > effects > > > because of absorption of outgoing longwave radiation with re-radiation at > > a > > > lower temperature > > > > 8. It can affect boundary layer stability which could have effects on > > clouds > > > etc. > > > > 9. Increased water vapor could affect cloud droplet size which would > > affect > > > cloud albedo. > > > > The importance of these different processes are likely to vary with > > > location. I do not think anybody's understanding of the climate system is > > > good enough to quantify each of these effects in their head without doing > > > detailed calculations. > > > > Surprisingly, in the NCAR CAM3 model, converting sensible heat to latent > > > heat was something like 3/4 as efficient at cooling as removing that > > energy > > > directly to space. My post-doc George Ban-Weiss is working on analyzing > > and > > > publishing these simulations. > > > > Best, > > > > Ken > > > > ___________________________________________________ > > > 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 > > > > On Sat, Dec 20, 2008 at 8:02 AM, <[email protected]> wrote: > > > >> Alvia & Stephen - One energy efficient arrangement would involve wind > > >> pumps on windy dry coasts. Direct wind is a great way to pump water, > > >> especially when you want to move more water to obtain more evaporation > > at > > >> higher wind speeds. You don't spray the water into the air, that is not > > >> energy efficient. Instead, you incorporate a vertical water lifting > > pipe up > > >> the side of a mountain and inside the wind turbine pylon. Then you drop > > the > > >> water as small droplets into the air and into waterfalls down the side > > of > > >> the mountain. > > > >> At 100% evaporation efficiency and 70% pump efficiency a 100 meter lift > > of > > >> 10,000 cubic meters per second requires 10,000 MW. Unfortunately, we > > need > > >> to figure out what to do with the accumulating tons of salt, on the > > order of > > >> 10 million cubic metes per year. Or we use more energy at some lower > > >> evaporation efficiency and attempt to disperse the brine in an > > >> environmentally acceptable fashion. Typical 100 meter tall wind > > turbines > > >> have nominal power ratings of 2 - 4 MW. > > > >> I wonder if we could convince California ski resorts and agribusinesses > > to > > >> fund a few large scale trials in hopes of getting more snow and rain. > > The > > >> process is also an ocean desalting project for dry coasts with on-shore > > >> winds. > > > >> Mark E. Capron, PE (Civil Engineer with 'day job' in water, recycled > > >> water, and wastewater) > > >> Oxnard, California > > >>www.PODenergy.org > > > >> -------- Original Message -------- > > >> Subject: [geo] Re: Ace Inventor Thinks He Can Rain in Global Warming > > >> From: Stephen Salter <[email protected]> > > >> Date: Sat, December 20, 2008 3:15 am > > >> To: [email protected] > > >> Cc: [email protected] > > > >> Hi All > > > >> The evaporation from the Ron Ace spray will certainly remove latent heat > > >> from the atmosphere but exactly the same amount of heat will be returned > > >> when the vapour condenses as rain somewhere else. While it remains as > > >> water vapour it will be adding to amount of the greenhouse gases and so > > >> working in the wrong direction. However if it condenses to form clouds > > >> where there were none before then these will reflect solar energy back > > >> out to space and will be doing what we want. If it adds to the liquid > > >> water content of existing clouds by making the drops in them bigger it > > >> will make them less reflective. Finally the cooling of the lower > > >> atmosphere will make it more stable and will reduce normal evaporation > > >> from the sea downwind of the spray source so reducing both vapour and > > >> cloud cover. One large eddy study, by a top-class atmospheric physicist > > >> who wishes to remain anonymous for fear of ridicule from less able ones, > > ... > > read more » --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
