The Resilience Hub & Portland Maine Permaculture Message Board › To slow global warming, install white roofs

To slow global warming, install white roofs

user 3022592
Portland, ME
Post #: 262­

Los Angeles Times
David S.
Washington, ME
Post #: 255
Interesting, but I don't understand it. Does the CO2 in the upper atmosphere eventually trap this heat? Considering how fast we are losing the white surface of the ice caps, would there be significant gain?
Merry H.
Portland, ME
Post #: 10
Fascinating. I wonder if, in climates like Maine, dark roofs help warm the interior of the house. It would be interesting to have tiles you could turn over summer to winter, much the way we reverse the direction/tilt of our ceiling fans. More practical, probably, would be a white "blanket" we could stretch over the roof for the summertime.
user 3022592
Portland, ME
Post #: 264
I don't understand it either, David. It was such a novel idea I decided to post it in case someone else would understand how it works, or, keeping the topic in mind, might see something later that explains it so ordinary people can get it.

Reversible tiles, Merry -- now that's novel too!
user 7662870
Portland, ME
Post #: 4
To get extremely technical... quantification relationships of the reflection of the sun's energy back to the atmosphere is called the 'albedo effect'. It's study is an important component of 'bioclimatology'. In the past, natural vegetation intercepted the sun's energy and used it in photosynthetic processes (which fixed atmospheric CO2 and released O2). Less energy actually made it to the ground. (Think about how cool it is in a dense forest even on the hottest day.) Mass deforestation and agricultural activities have changed that balance causing the exposed ground to heat more and less CO2 to be tied up within the vegetation. Increased warming has caused glaciers to recede thereby reducing reflection of the sun's energy AND exposing more ground to is a negative feedback loop!! Paving a large area in light-colored material mimics the albedo effect of a glacier.

White roof surfaces would have two main effects: 1.) Reflection of the the sun's energy back before it can be absorbed by the Earth's mass, and 2.) by preventing a roof from heating and transmitting it inside, the need for airconditioning will be reduced. A large component of electrical energy is produced by burning fossil fuels which release more CO2.

Another benefit of using light-colored roofing material is that they last longer than darker you save money in the long run.

David S.
Washington, ME
Post #: 258
Interesting information. I sorta knew that before. It didn't really answer my questions though and created another. Is the reflected heat still trapped in the upper atmosphere?

Most of all I would like to have seen a graph of changes in the albedo effect over a period of time. Is it decreasing rapidly with the losses of the ice caps?

I was also thinking along Merry's lines. Would a dark roof in the winter have any effect on heating your house? It seems that design changes would be needed since most homes have a lot of insulation in the roof. Then there is night time............
user 7662870
Portland, ME
Post #: 5
Yes, I would think that some of that reflected energy would be trapped by the atmosphere depending on the CO2 levels and the season. The albedo effect is a ratio of reflectivity from various materials...not a measure of heat. I do not believe that the regional changes have been synthesized into a cohesive global determination nor of the effect on least that I have seen. There does seem to be more data on local changes though. Here is an interesting link from the EU.

Technically, 'yes' to Merry's question BUT....Most houses' living spaces in Maine are insulated away from the roof. It only heats the attic. Attics are usually open to the environment to allow moisture to disperse. Heated air would leave through the vents and cold fresh air would be sucked in. One would have to roll up their attic insulation and block off the ventilation when the sun was shining and then roll it back down when the sun went down.
David S.
Washington, ME
Post #: 261
If the ice caps are disappearing then it would seem that the albedo effect must be decreasing as well. A worldwide measue of this over a period of tim would be useful.

Then there's this:

By Juliet Eilperin
Washington Post Staff Writer
Friday, September 26, 2008; Page A02

The rise in global carbon dioxide emissions last year outpaced international researchers' most dire projections, according to figures being released today, as human-generated greenhouse gases continued to build up in the atmosphere despite international agreements and national policies aimed at curbing climate change.

In 2007, carbon released from burning fossil fuels and producing cement increased 2.9 percent over that released in 2006, to a total of 8.47 gigatons, or billions of metric tons, according to the Australia-based Global Carbon Project, an international consortium of scientists that tracks emissions. This output is at the very high end of scenarios outlined by the Intergovernmental Panel on Climate Change (IPCC) and could translate into a global temperature rise of more than 11 degrees Fahrenheit by the end of the century, according to the panel's estimates.

"In a sense, it's a reality check," said Corinne Le Quéré, a professor at the School of Environmental Sciences at the University of East Anglia and a researcher with the British Antarctic Survey. "This is an extremely large number. The emissions are increasing at a rate that's faster than what the IPCC has used."

The new statistics also underscore the growing contribution to the world's "carbon budget" from rapidly industrializing countries such as China, India and Brazil. Developing nations have roughly doubled their carbon output in less than two decades and now account for slightly more than half of total emissions, according to the new figures, up from about a third in 1990. By contrast, total carbon emissions from industrialized nations are only slightly higher than in 1990.

"What's happening is the major developed countries' plans are converging for emissions growth that will stop and be able to come down significantly," said James L. Connaughton, who chairs the White House Council on Environmental Quality. "But that's being completely overtaken now by the increasing greenhouse gas emissions in developing counties. It underscores the need for a broader and more aggressive effort by the major economies to come together."

It is unclear how much industrialized countries will be able to reduce their carbon output in the years to come, regardless of whether developing nations seek to restrain their greenhouse gas emissions. The federal government predicts that U.S. fossil fuel consumption will increase, not decrease. Japan, Canada and several other countries that committed to reducing their carbon emissions under the 1997 Kyoto Protocol have fallen far behind in meeting their targets.

Moreover, new scientific research suggests Earth is already destined for a greater worldwide temperature rise than previously predicted. Last month, two scientists from the Scripps Institution of Oceanography and the University of California at San Diego published research showing that even if humans stopped generating greenhouse gases immediately, the world's average temperature would "most likely" increase by 4.3 degrees Fahrenheit by the end of this century. Writing in the journal Proceedings of the National Academy of Sciences, they based their calculations on the fact that new air-quality measures worldwide are reducing the amount of fine particles, or aerosols, in the atmosphere and diminishing their cooling effect.

The IPCC has warned that an increase of between 3.2 and 9.7 degrees Fahrenheit could trigger massive environmental changes, including major melting of the Greenland ice sheet, the Himalayan-Tibetan glaciers and summer sea ice in the Arctic. The prediction that current emissions put the planet on track for a temperature rise of more than 11 degrees Fahrenheit, Le Quéré said, means the world could face a dangerous rise in sea level as well as other drastic changes.

Richard Moss, vice president and managing director for climate change at the World Wildlife Fund, said the new carbon figures and research show that "we're already locked into more warming than we thought."

"We should be worried, really worried," Moss said. "This is happening in the context of trying to reduce emissions."

The new data also show that forests and oceans, which naturally take up much of the carbon dioxide humans emit, are having less impact. These "natural sinks" have absorbed 54 percent of carbon dioxide emissions since 2000, a drop of 3 percent compared with the period between 1959 and 2000.

Connaughton argued that the Bush administration's "major economies" meetings, a series of talks among both developed and rapidly industrializing nations, have moved the world closer toward achieving significant cuts in greenhouse gases because the group is developing a common measurement system for emissions and is exploring how different industrial sectors can commit to worldwide reductions.

"We are unquestionably moving toward each other," he said of the industrialized and developing countries, "but there's a ways to go."

But Moss, who characterized the latest round of negotiations as "a lot of talk but not much action," said the administration cannot expect emerging economies to constrain their carbon emissions when the United States has yet to adopt binding targets for cutting its greenhouse gases. He noted that since 1990, the United States has released about 30 gigatons of carbon into the atmosphere, compared with China's seven gigatons and India's one.

"We really do have to start showing some leadership and start doing some changes ourselves," he said. "If we did that, China and India, which are developing rapidly, would be willing to come along."
user 7662870
Portland, ME
Post #: 6

Hi all. Someone was kind enough to point out that the situation I described above is actually a POSITIVE FEEDBACK LOOP! I was thinking in terms of it being a 'bad' thing when I wrote "negative feedback loop." shock Sorry for any confusion that may have caused!
A former member
Post #: 3
Paul's earlier point regarding the likely insignificance of 'heating one's home with a dark roof' is right on. Any heat gained by a dark roof in winter would be lost to the atmosphere - the airspace and insulation of the attic preclude that heat getting to the living space. A dark roof does help melt off the snow - a good thing from the standpoint of snow loads and ice damming, but a bad thing from the standpoint of the insulative effect of a good blanket of snow (also minimal on the roof, given the attic and insulation space).

The importance of the white roof in terms of albedo effects is not limited to just summer time; global warming is a long term, cumulative, and pervasive issue. Think of terra firma and our atmosphere as the biggest heat sink around - so the loss of large scale reflectivity is not just a summer issue.

In the process of googling 'albedo effects over time' I found this link to one study of white roofs, which also has some other suggestions... http://www.treehugger...­

Also of interest: http://en.wikipedia.o...­

In terms of measuring the increase of albedo over time, a quick search did not easily find charts online; further searches at NOAA, etc might find something... but remember that albedo is but one part of the overall global warming picture, with many variables - favorable and not so - as climate change's multiples effects work their way thru the system. For example, global warming might cause more cloud cover, increasing albedo (higher reflectivity of clouds compared to landforms or vegetation), but also increasing global warming (as clouds help to retain heat).

Fun stuff! Scary stuff!
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