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" derekgwfidd...@dodo.com.au > > 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 > > > > > > > > > > > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to geoengineering@googlegroups.com To unsubscribe from this group, send email to geoengineering+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
