. . . . 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 -~----------~----~----~----~------~----~------~--~---
