*sorry .. I just woke up (6 AM here) and am pre-coffee. Didn't seen it was cars only.*
On Fri, 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 20–30 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 20–30 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 130–150 Gigatonnes of carbon. Using the MODIS data for urban >> areas, in contrast, would cool the Earth by 0.01 K, equivalent to 25–30 >> 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. >> > > -- 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.
