Sea ice acts to insulate the underlying water from the cold atmosphere. In the absence of sea ice, heat fluxes into or out of the surface can easily increase by more than an order of magnitude.
___________________________________________________ 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 29, 2008 at 8:42 AM, Stephen Salter <[email protected]> wrote: > > . . . . but the latent heat of ice is hugely greater than the specific > heat of water. Freezing one metre of ice is like cooling an 80 metre > depth of sea by 1 K. > > Stephen > > [email protected] wrote: > > Re Arctic ice, the issue is not just albedo, but also thermai > > inertia. The effective heat capacity of the exposed ocean is > > hugely greater than the ice. > > > > Tom. > > > > ++++++++++++++ > > > > > >> > http://www.celsias.com/article/all-about-albedo-lighter-world-cooler-world/ > >> > >> All About Albedo: A Lighter World is a Cooler World > >> Jeremy Williams > >> > >> >From the latin 'albus', meaning 'white', albedo is an indicator of > >> > >>> reflectivity. Bright objects reflect much of the light that reaches > them, > >>> and have high albedo. Dark objects have low albedo, because they absorb > >>> light. If you've ever climbed into a dark-colored car on a hot day, you > >>> already understand albedo. It's an unusual word, and an unusual factor > in > >>> climate change, presenting both dangers and and opportunities. > >>> > >> The danger comes primarily from the Arctic, where vast sheets of white > ice > >> reflect sunlight away from the earth and have a cooling effect on the > >> atmosphere. Ice is highly reflective, reflecting 80-90% of sunlight > >> (pdf), but seawater is dark blue or green and reflects very little. As > >> Arctic ice melts, seawater takes its place, which absorbs more heat and > >> compounds the melting problem. Loss of albedo in this context becomes an > >> accelerator of climate change. > >> > >> This works in reverse in the case of deforestation, something I learned > a > >> few years ago when I had flying lessons in Kenya's Rift Valley. We flew > >> across the transition from forested escarpment to desert valley floor, > and > >> the rising heat off the dusty plains created great waves of turbulence > >> that tossed our little plane around. Forests, being dark, absorb 95% of > >> the sunlight that falls across them, whereas cleared land or desert has > a > >> higher albedo and beams that light and heat back up. Interestingly, > >> deforestation actually raises the earth's albedo. > >> > >> Before we get the chainsaws out however, we should remember that forests > >> use some of the sunlight in photosynthesis. They also help create > clouds, > >> and of course absorb CO2 from the atmosphere. Overall, their net effect > is > >> usually cooling. > >> > >> I say usually because research by the Global Carbon Project found that > >> there is in fact a case for deforestation (pdf) to cool the earth in > >> some places. In tropical countries and mid-latitude areas forests have a > >> cooling effect. But "high latitude forests have a strong warming > >> influence, largely due to the presence of dark forest canopies in > regions > >> that would otherwise be snow covered." > >> > >> As well as giving us some complicating factors in forestation and Arctic > >> ice, albedo presents us with some interesting opportunities. If > reflective > >> surfaces have a cooling effect on the earth, can we create some more of > >> them? > >> > >> There are two immediate possibilities. The first of these is the urban > >> environment, which covers around 1% of the earth's surface. In research > >> earlier this year, two scientists at the Lawrence Berkeley National > >> Laboratory in California discovered that whitening our cities (pdf) > >> could have a considerable cooling effect. "Increasing urban albedo can > >> result in less absorption of incoming solar radiation by the > >> surface-troposphere system, countering to some extent the global scale > >> effects of increasing greenhouse gas concentrations." It would also cool > >> the air on the ground, reducing the need for air conditioning in the > >> summer. > >> > >> The report estimated that around 40% of the urban environment is > pavement > >> and 20-25% is roofs, both of which could be made more reflective. Most > >> pavements and parking lots are laid in Portland cement concrete, which > is > >> expensive when totally white, but can be easily made lighter with > >> different aggregates (pdf). White asphalt shingles, corrugated iron, > or > >> white acylic tiles can be used for roofing. You can read the maths for > >> yourself, but the authors conclude that whitening the urban environment > >> would offset the equivalent of 44 Gigatonnes of CO2, or 11 years worth > of > >> growth in CO2 emissions. That's an offset, so it would not affect > climate > >> change in the long term, but it would buy us some time while we bring > >> emissions under control. > >> > >> A second, more radical idea is the Global Albedo Enhancement Project , > >> which suggests we cover large areas of the earth with white polythene > >> film. According to Alvia Gaskill, the originator of the idea, covering a > >> large enough area of the earth "could be expected to offset some or all > of > >> the projected additional radiative forcing and global warming from 2010 > to > >> 2070." Prime locations would be the Sahara, Arabian or Gobi deserts, > where > >> thousands of square miles of desert could be covered. > >> > >> As geo-engineering goes, it's a fairly conservative idea, and the > plastics > >> technology already exists. On the downside, the cover would kill every > >> living thing in the area, and would need to stay in place for at least a > >> century. Local weather patterns may be affected. Windblown dust may > lower > >> the albedo of the plastic as it gets dirty, but Gaskill suggests robotic > >> vacuum cleaners to keep them clean. > >> > >> This may be the more outlandish end of albedo research, but expect to > hear > >> more about it - albedo is one of many new factors that will be added to > >> climate change models in coming years. In the meantime, why not get some > >> white paint, and get started on your own roof? > >> > >> Related Reading: > >> Climate Change Ahead of Schedule > >> NOAA's 2008 Arctic Report Card > >> > >> Image Credit: > >> International Polar Foundation > >> > >> 1 comment > >> If you see any unhelpful comments, please let us know immediately. > >> > >> Pacific Trasher (anonymous) > >> The easiest way to change the earth's albedo would be to tweak the > >> manufacture of our 5 trillion plastic bags per year, to make them white > >> and bright. We already know how to get this stuff into the North Pacific > >> Gyre (aka the Pacific garbage patch) and other places. Instead of > massive > >> investment in new technology, only a small behavior change would be > >> needed: instead of recycling or landfilling grocery bags, styrofoam, > etc. > >> get them into streams and storm drains, en route to the earth's dark > >> oceans, which absorb tremendous amounts of radiant energy. The EARTH BAG > >> would be white, with two small flotation capsules under the handles. > >> Unlike large areas of plastic, floating plastic bags would allow fish, > >> birds, and other creatures access to the surface when needed. > >> > >> If cooling were to progress too far, we could quickly and easily tweak > the > >> manufacture so as to make the bags slightly darker. > >> > >> Such a strategy would be inclusive. Everyone on earth could help stop > >> global warming and spread the bags, not just a favored contractor or > two, > >> or those wealthy enough to afford solar panels or a Prius. > >> > >> This is the White Trash solution. As Dustin Hoffman was advised in THE > >> GRADUATE, the future is one word: Plastics. > >> > >> Written this month > >> > >> NOTE: Pacific Trasher is in reality managingwholes.com, a recycling > based > >> site in Oregon. They sent me the following message several days ago: > >> > >> "Alvia, saw your proposal to change the albedo. I'm probably not the > first > >> to suggest this, but the Pacific garbage patch is already proof of > >> concept. We manufacture 5 trillion plastic bags per year. Instead of > dark > >> and beige, the new watchword will be light and bright. The Earth Bag > will > >> be the new grocery standard: white with small flotation capsules under > >> each handle, like bubble wrap capsules. > >> > >> Social change would be required--maybe not in Tunisia, but in the U.S. > >> Instead of dutifully recycling or landfilling these bags, or foregoing > >> their use, it would become socially responsible to throw them > everywhere, > >> especially in streams or storm drains where they could make their way to > >> the dark oceans. > >> > >> Unlike the large sheets that you propose, a multitude of floating or > >> drifting bags would allow wildlife to use the intervening space. > >> > >> Instead of relying on a few large contractors to implement an albedo > >> solution, we have a more democratic approach. Everyone can contribute. > Not > >> just bags, but white styrofoam chunks, styrofoam packing peanuts, etc. > >> > >> I call this the White Trash solution. > >> > >> happy new year" > >> > >> To which I responded: > >> > >> "Due to biofouling, the growth of algae and bacteria on the surfaces of > >> the floating material, the albedo impact would be negligible. For this > >> and ecological reasons, I recommend "bagging" this idea." > >> > >> And while on the subject of albedo enhancement, Dereck Fiddler from > >> Australia informs of his recent calculations of the impact of > implementing > >> urban whitening on CO2 offsets as per the LBNL recommendations as well > as > >> on my erroneous wording. His conclusions are included in the > attachment. > >> > >> > >> From: > >> "Derek Fiddler" [email protected] > >> > >> Hi Alvia, > >> > >> There's a word wrong on the website> > >> > >> > http://www.global-warming-geo-engineering.org/Albedo-Enhancement/Executive-Summary/Albedo-Enhancement/ag7.html > >> > >> On your webpage "Princilple" 2.4.1 > >> > >> You've got > > >> > >> Finding ways to reduce the albedo of cities would, therefore, be very > >> helpful > >> > >> > >> I'm sure you mean "increase albedo"? :-) > >> > >> I recently calculated the CO2e offsets for Australia's Capital Cities > >> using a .1 albedo increase and a 0.91 watts to CO2e ratio as per the > Heat > >> Island Group. The Heat Island Group suggest a 7.5% increase. Attached: > >> cities.pdf > >> > >> The latest version of the Albedo Calculators allows the watts to CO2re > >> ratio to be set to any value so that various scenarios or changes in the > >> ratio over time can be modelled. > >> > >> Best wishes, > >> > >> > >> Regards... Derek. > >> > >> > >> Att: cities.pdf > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > > > > > > > > > > > > > > > > > -- > The University of Edinburgh is a charitable body, registered in > Scotland, with registration number SC005336. > > > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
