Indeed‹my new ones have been on for a couple of weeks now, and are producing 60 kw-hr/day (something like a 25% capacity factor) on sunny days in early April, so a good bit more than we would have been using even if we were here.
Mike On 4/13/12 10:36 AM, "Alan Robock" <[email protected]> wrote: > Not to mention the advantage of putting solar panels on the roofs instead of > painting them. > > Alan > > Alan Robock, Professor II (Distinguished Professor) > Editor, Reviews of Geophysics > Director, Meteorology Undergraduate Program > Associate Director, Center for Environmental Prediction > Department of Environmental Sciences Phone: +1-732-932-9800 x6222 > Rutgers University Fax: +1-732-932-8644 > 14 College Farm Road E-mail: [email protected] > New Brunswick, NJ 08901-8551 USA http://envsci.rutgers.edu/~robock > > On Apr 13, 2012, at 5:57 AM, Ken Caldeira <[email protected]> wrote: > >> The scientists estimated that urban areas make up roughly 1% of the total >> land area in these regions; increasing albedo by 0.1 only in urban areas >> would be equivalent to a global change in land-surface albedo of 0.001. >> "Increasing albedo of urban areas by about 0.1 increasing flat roof albedo >> by 0.4, increasing sloped roof albedo by 0.25, and pavement albedo by 0.15 >> cools the globe equivalent to offsetting over 100 Gigatonnes of carbon >> dioxide emissions," said Akbari. "This is equivalent to offsetting the >> emissions for all the cars in the world for the next 2030 years." >> >> A global change in land surface albedo of 0.001 is a change in global surface >> albedo of 0.0003. >> >> If half the land is under clouds this might lead to a global >> top-of-atmosphere albedo change of something like 0.00018. >> >> A doubling of CO2 can be compensated by a global albedo change of 0.018, >> which suggests that an urban albedo change 0.01 would have a result that is >> about 100 times smaller. >> >> If a doubling of CO2 occurs in a century, this suggests this approach could >> delay warming by 1 year, not 20 to 30 years as claimed in this news report. >> >> Perhaps Damon or Hashem can shed some light on this apparent discrepancy. >> >> Another question is the relative benefits of greening cities versus whitening >> cities. >> >> >> _______________ >> Ken Caldeira >> >> Carnegie Institution Dept of Global Ecology >> 260 Panama Street, Stanford, CA 94305 USA >> +1 650 704 7212 [email protected] >> http://dge.stanford.edu/labs/caldeiralab @kencaldeira >> >> Currently visiting Institute for Advanced Sustainability Studies (IASS) >> <http://www.iass-potsdam.de/> >> and Potsdam Institute for Climate Impact Resarch (PIK) >> <http://www.pik-potsdam.de/> in Potsdam, Germany. >> >> >> >> On Fri, Apr 13, 2012 at 5:37 AM, Andrew Lockley <[email protected]> >> wrote: >>> >>> Increasing albedo - why we should paint the roof white to reduce energy use >>> in summer http://environmentalresearchweb.org/cws/article/news/49268 >>> >>> Replacing roofs and pavements with more reflective versions when they wear >>> out could cut global temperatures by up to 0.07 °C, equivalent to a >>> reduction in carbon-dioxide emissions of around 150 billion tonnes. That's >>> according to researchers in Canada who used a global climate model to look >>> at the effects of albedo changes in urban areas. >>> >>> "Scientists have been proposing novel ideas mostly untested for >>> geoengineering of global climate," Hashem Akbari of Concordia University >>> told environmentalresearchweb. "Humans have had experience with white >>> buildings and reflective pavements for thousands of years without any >>> unknown negative side-effects. Hence cool urban surfaces should be our >>> geoengineering 101." >>> >>> Akbari and colleagues from Concordia used the University of Victoria Earth >>> System Climate Model (UVic ESCM) to investigate the effect of albedo >>> increases of 0.1 until 2300 over all land between latitudes of + and 20° >>> (i.e. roughly from Mexico City and Hanoi in the north to Bulawayo, Zimbabwe >>> in the south), and between + and 45° (approximately from Lyon, France and >>> Portland, US to Dunedin in New Zealand). The team used both a >>> business-as-usual emissions scenario and an aggressive mitigation scenario. >>> >>> The albedo increase on all land between + and 20 ° latitude would decrease >>> temperature by roughly one degree over 20 years, while the 45° latitude case >>> would double this decrease. After 200 years, the decreases would be 1.3 K >>> and 3 K. >>> >>> The scientists estimated that urban areas make up roughly 1% of the total >>> land area in these regions; increasing albedo by 0.1 only in urban areas >>> would be equivalent to a global change in land-surface albedo of 0.001. >>> >>> "Increasing albedo of urban areas by about 0.1 increasing flat roof albedo >>> by 0.4, increasing sloped roof albedo by 0.25, and pavement albedo by 0.15 >>> cools the globe equivalent to offsetting over 100 Gigatonnes of carbon >>> dioxide emissions," said Akbari. "This is equivalent to offsetting the >>> emissions for all the cars in the world for the next 2030 years." >>> >>> To firm up their calculations, the researchers employed two estimates of >>> urban area from the Global Rural and Urban Mapping Project (GRUMP) and an >>> analysis based on MODIS satellite data. The GRUMP results suggest that >>> global urban areas are more than five times larger than the MODIS data set >>> indicates. >>> >>> The climate model revealed that increasing albedo by 0.1 only in >>> GRUMP-designated urban areas would produce long-term cooling of 0.07 K, >>> equivalent to 130150 Gigatonnes of carbon. Using the MODIS data for urban >>> areas, in contrast, would cool the Earth by 0.01 K, equivalent to 2530 >>> Gigatonnes of carbon. >>> >>> According to Akbari, albedo increases could lead to air-conditioning savings >>> of about 20% for space under the roof. "This is about $50 bn savings per >>> year and carbon dioxide savings of about 0.4 Gigatonnes per year; over the >>> next 100 years that is an emission reduction of 40 Gigatonnes," he said. >>> "The direct cooling of the Earth by reflecting radiation back to space is an >>> added bonus that actually counters global warming while putting dollars in >>> our pocket." >>> >>> The researchers found that the effect of albedo change did not depend to a >>> large extent on the carbon-dioxide emissions scenario. That said, aggressive >>> mitigation appeared to produce a roughly 10% larger temperature decrease, >>> which the team ascribed to stronger snow-albedo feedback. >>> >>> "We should develop policies for no-regret no-cost global cooling measures," >>> said Akbari. "Cool cities will save all the people in the world equally and >>> the value of the dollar saved is significantly higher in developing >>> countries than the developed country (e.g. $1 saved in the US pays for 10 >>> minutes of a labourer in the US; in the developing countries that pays for a >>> day of labourer)." -- 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.
