Global warming solutions? - geo-engineering? PV cells?

Now that have threads on global warming sceptics and on global warming underway, time for a thread on

Potential ways of reducing warming

Just in UK newspaper The Independent:

A Nobel Prize-winning scientist has drawn up an emergency plan to save the world from global warming, by altering the chemical makeup of Earth's upper atmosphere. Professor Paul Crutzen, who won a Nobel Prize in 1995 for his work on the hole in the ozone layer, believes that political attempts to limit man-made greenhouse gases are so pitiful that a radical contingency plan is needed.

In a polemical scientific essay to be published in the August issue of the journal Climate Change, he says that an "escape route" is needed if global warming begins to run out of control. Professor Crutzen has proposed a method of artificially cooling the global climate by releasing particles of sulphur in the upper atmosphere, which would reflect sunlight and heat back into space. The controversial proposal is being taken seriously by scientists because Professor Crutzen has a proven track record in atmospheric research. ...

Such "geo-engineering" of the climate has been suggested before, but Professor Crutzen goes much further by drawing up a detailed model of how it can be done, the timescales involved, and the costs. In his forthcoming scientific paper, Professor Crutzen emphasises that the best way of averting global climate disaster is for countries to cut back significantly on their emissions of greenhouse gases, notably carbon dioxide produced by burning oil, gas and coal. But in the absence of such measures, and with the average global temperature expected to rise more than 3C this century, there may soon come a time when more extreme measures have to be considered, he said. ...

His plan is modelled partly on the Mount Pinatubo volcanic eruption in 1991, when thousands of tons of sulphur were ejected into the atmosphere causing global temperatures to fall.

[url=http://www.independent.co.uk/environment/scientist-publishes-escape-rout...

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George Monbiot, writing in the Guardian, figures the sulphate idea is risky; sulphates could have adverse impacts on rainfall patterns, as happened over North Africa (where main rainfall bands shifted southwards, causing massive impacts): We">http://www.guardian.co.uk/commentisfree/story/0,,1860299,00.html]We can't reverse global warming by triggering another catastrophe

Sulphate pollution killed hundreds of thousands of Africans. A plan to use sulphur to fight climate change risks the same

The US is set to begin experiments on storing carbon dioxide below ground, especially in underground saline aquifers; might be one way we can burn our coal and keep earth from warming too much.

The same rock chambers that held oil and natural gas for millions of years also locked up carbon dioxide. For 30 years, the oil and gas industry has pumped carbon dioxide into waning oil fields to get at the last drops. By some estimates, those depleted deposits alone could hold 20 to 30 years of carbon dioxide released from all U.S. coal-fired power plants. Coal beds that are too deep or otherwise uneconomical to mine also could hold billions of tons of carbon dioxide, while releasing methane back to the surface as an energy supply. But the biggest reservoirs are deep, saline aquifers that underlie the Midwest, the Southeast and places like the Central Valley, some as ancient as the emergence of multi-cellular organisms and plants on the Earth and many times saltier than the ocean. Those underwater seas are big and numerous enough to hold at least 100 years worth of U.S. emissions from all large stationary sources, from refineries to power plants to steel factories.

Delta">http://www.insidebayarea.com/dailyreview/localnews/ci_4426749]Delta could unlock key in global warming fight Scientists want to try pumping carbon dioxide underneath farmland

... the challenge of tackling climate change could create a market of up to £30bn for British business over the next ten years. The research also identifies major opportunities for small and medium sized enterprises in a wide range of markets, by both responding to consumer demand for environmentally friendly goods and to demands created by government action. The biggest identified markets for SMEs in 2010 will be: Building regulations for commercial and industrial use - £950m Renewable electricity - £800m Renewable road transport fuels - £500m Domestic energy efficiency - £400m Building regulations for domestic use - £275m ...

New">http://www.shell.com/home/Framework?siteId=uk-en&FC2=/uk-en/html/iwgen/n... report on business and climate change for Shell Springboard

Now, on Science website, an idea for reducing sun reaching the earth by having screen of tiny spacecraft - each a transparent disc.

... one astronomer has come up with a radical plan to cool Earth: launch trillions of feather-light discs into space, where they would form a vast cloud that would block the sun's rays. ... Instead, University of Arizona Steward Observatory optics expert Roger Angel proposes using screens just 0.6 meters across, weighing about a gram each. These discs would be manufactured on Earth using very thin, transparent material that doesn't reflect the sun, but instead refracts it, so as to avoid having the sun's radiation push them out of orbit. The discs would also have three 0.1-meter-long protruding electronic "ears" with a solar power source so they could adjust their position, making them essentially tiny spacecraft.

so far, so good, perhaps, but then:

About 16 trillion flyers would have to be deployed, which could be done with 20 launchers that would each send up a stack every 5 minutes for 10 years.

yeah, right - like governments are about to get their acts together enough to do this. (And what if get too much cooling, or other problems, anyway?) A">http://sciencenow.sciencemag.org/cgi/content/full/2006/1031/3]A Sunshade for Planet Earth

I've seen ideas re sprinkling iron across ocean surfaces, to enhance plankton growth in bid to soak up more carbon dioxide. But, maybe not a great idea after all:

Ocean currents that stimulate marine organisms by sucking up carbon and nutrients from the sea bottom don't seem to mitigate the buildup of carbon dioxide in Earth's atmosphere--and they might even constitute a net source of the greenhouse gas--new research suggests.

... The researchers were able to track what happens to carbon that comes up from the deep and how it supports the local plankton populations. They found that a lot of the carbon fails to sink back down to the depths. Instead, it is recycled as organic matter, where it remains in the surface waters and can even be ejected into the atmosphere as carbon dioxide, says chemical oceanographer Claudia Benitez-Nelson of the University of South Carolina in Columbia and lead author of the Hawaii paper. ...

Don">http://sciencenow.sciencemag.org/cgi/content/full/2007/517/2]Don't Bet on the Bloomin' Plankton - Science news; need subscription to view after a month.

Email from Worldwatch had upbeat item on photovoltaic cells, which may help reduce our reliance on fossil fuels.

The solar industry is poised for a rapid decline in costs that will make it a mainstream power option in the next few years,according to a new assessment by the Worldwatch Institute in Washington, D.C., and the Prometheus Institute in Cambridge, Massachusetts.

Global production of solar photovoltaic cells, which turn sunlight directly into electricity, has risen sixfold since 2000 and grew 41 percent in 2006 alone. Although grid-connected solar capacity still provides less than 1 percent of the world's electricity, it increased nearly 50 percent in 2006, to 5,000 megawatts, propelled by booming markets in Germany and Japan. Spain is likely to join the big leagues in 2007, and the United States soon thereafter.

Solar">http://www.worldwatch.org/node/5086]Solar Power Set to Shine Brightly

Mentions China's largest photovoltaic cells producer, Suntech Suntech">http://www.suntech-power.com/]Suntech Power website looks well worth a visit. Includes:

Some sunny facts on solar energy:

* The Sun has sufficient helium mass to provide the Earth with energy for another 5 billion years and, every 15 minutes, it emits more energy than humankind uses in an entire year.

* The Earth receives only one half of one billionth of the Sun’s radiant energy, but, in just a few days, it gets as much heat and light as could be produced by burning all the oil, coal and wood on the planet.

* The Sun represents 99.8% of the total mass of our solar system, its surface temperature is 6000ºC, and its total energy could melt an ice cube the size of planet Earth in just 30 minutes.

* Worldwide, some 2 billion people are still without electricity and, for these populations, it is more economically viable to install solar panels than to extend established electricity grids.



Post edited by: Martin, at: 2007/05/28 08:48

In letter to Nature, James Lovelock (of Gaia hypothesis) and Chris Rapley suggest using:

free-floating or tethered vertical pipes to increase the mixing of nutrient-rich waters below the thermocline with the relatively barren waters at the ocean surface.... Water pumped up pipes — say, 100 to 200 metres long, 10 metres in diameter and with a one-way flap valve at the lower end for pumping by wave movement — would fertilize algae in the surface waters and encourage them to bloom. This would pump down carbon dioxide and produce dimethyl sulphide, the precursor of nuclei that form sunlight-reflecting clouds.

Ocean">http://www.nature.com/nature/journal/v449/n7161/full/449403a.html#a1]Ocean pipes could help the Earth to cure itself Article on Nat Geog site says they've done laboratory experiments showing this may be feasible, and now have sponsor to start small scale trial. But, plenty of uncertainties - the pipes may exhale CO2 as process begins, then may disrupt ocean cycles and impact marine life. Giant">http://news.nationalgeographic.com/news/2007/09/070926-warming-solution.... Ocean Tubes Proposed as Global Warming Fix

Wave power seems promising as way to help reduce reliance on burning fossil fuels. BBC reporting on large test project to start in Scotland.

One of the world's largest wave energy projects is to be unveiled off the coast of Orkney. First Minister Alex Salmond is to open the new testing facility for tidal energy at the European Marine Energy Centre (EMEC) in Stromness. The site will house four wave energy converters, capable of generating electricity for 2,000 homes. The centre is said to be the first of its kind in the world to provide a purpose-built testing facility.

Plan">http://news.bbc.co.uk/2/hi/uk_news/scotland/north_east/7017325.stm]Plan to harness Orkney wave power

Another idea for reducing CO2 in the atmosphere; again, I think, looking fanciful - helps get publicity for researchers' projects, ao maybe good for grant money, but doubt this will save us all (in fairness, not touted as great cure).

The technology, invented by Kurt Zen House, a PhD candidate at Harvard's Department of Earth and Planetary Sciences, and co-workers, involves electrochemically removing hydrochloric acid from the ocean, neutralizing it by reaction with silicate rocks and returning it to the sea. By increasing ocean alkalinity, the process would enhance the absorption of atmospheric CO2. Over time, the CO2 would mix throughout the ocean and eventually precipitate as calcium carbonate in ocean sediments.

Nature">http://www.nature.com/climate/2007/0712/full/climate.2007.67.html]Nature's cure

Here's another idea - note, too, re how little effort being put into seeing if may be viable, compared to politicians wandering the planet spouting hot air on the issue.

Professor Stephen Salter, a renowned engineer working at Edinburgh University, has hatched a plan to produce white clouds over the ocean to halt the catastrophic water heating associated with global warming.

In the worst-case scenario, where global "tipping points" such as the melting of the Arctic ice cap are reached, he claimed launching a fleet of cloud-producing drone ships could save Earth. advertisement

Salter, who is famed for inventing the "duck", a device that generates power by bobbing on waves, said: "We've got an explosive with the detonator in it, and when one goes off, it could trigger other explosives. That's why we need to have a number of solutions. I don't mean that we should continue burning coal and then just fix the consequences, that would be terrible. Just as a revolver has many bullets, we need several ideas." ... Salter's idea, which he formed in collaboration with John Latham, of the National Centre for Atmospheric Research in Colorado, is to build boats to sail the ocean and produce a spray of tiny water droplets around which white clouds can form. He suggested that around 400 of these wind-powered boats would be needed, at a cost of £100 million. However, the difficult part would be producing droplets small enough for clouds to form, a technique Salter has yet to master. His struggle has been a lonely one so far, and he holds little faith in government.

Salter said: "In the UK, there is one old aged pensioner, me, and one PhD student in Leeds working on cloud control, and that is it. Then there are politicians travelling the world, holding meetings to say how awful it is and the only outcome is that they organise another meeting to say the same."

Cloud-making">http://www.sundayherald.com/news/heraldnews/display.var.2104840.0.cloudm... plan to reverse global warming Edinburgh University professor advocates revolutionary response to crisis

A proposed solution to reverse the effects of global warming by spraying sulfate particles into Earth's stratosphere could make matters much worse, climate researchers said on Thursday.

They said trying to cool off the planet by creating a kind of artificial sun block would delay the recovery of the Antarctic ozone hole by 30 to 70 years and create a new loss of Earth's protective ozone layer over the Arctic.

"What our study shows is if you actually put a lot of sulfur into the atmosphere we get a larger ozone depletion than we had before," said Simone Tilmes of the National Center for Atmospheric Research in Boulder, Colorado, whose research appears in the journal Science.

Plan">http://www.reuters.com/article/environmentNews/idUSN2435161220080424]Plan to reverse global warming could backfire

Excerpts from "Seven Wonders for a Cool Planet: Everyday Things to Help Solve Global Warming," by Eric Sorensen and the staff of Sightline Institute, copyright (c) 2008 by Sightline Institute (Published by Sierra Club Books) appear in Seattle Times. Including:

Seven Wonders is a way to think — illustrated seven ways — about solving the climate crisis. It's a way to reimagine the problem, starting with a few mostly low-tech tools and notions. ... The Bicycle A human on a bicycle is more efficient (in calories expended per pound and per mile) than a train, airplane, boat, automobile, canoe or jet pack. Bicycles are sustainable wonders ... The Condom Today, human beings will have sex more than 100 million times. Today's sex will also make one million women around the world pregnant — about half of them unintentionally. ... A billion fewer humans might spare the planet perhaps 4 billion tons of carbon-dioxide emissions each year. ... The Ceiling Fan ... Better energy efficiency doesn't necessarily mean investing in new technologies. Much of the time, a ceiling fan will be enough for keeping cool. Even when it's not, with a fan going, you can set a thermostat 9 degrees higher and feel just as comfortable — and save about a third off your cooling (and global-warming) bill. ... The Clothesline In an hour and 15 minutes, the Earth receives as much energy in the form of sunlight as humans officially use in a year. ... The clothesline is only the most obvious way to tap into the renewable energy all around us. I... The Library Book The essential wonder of libraries is that they reduce the need for newly manufactured goods. ... The Microchip ... as we make and move less stuff, we save energy. ... The Real Tomato ... even in the peak of summer, when tomatoes are ripening in gardens around the country, American supermarkets will sell mass-produced hothouse tomatoes from Canada and Roma tomatoes from Mexico. ... The problems arising from animal agriculture are vexing enough with just one in four people worldwide eating a meat-centered diet. There's no way the world can support 6 billion — much less a future population of 8 to 12 billion — heavy meat eaters. Eating organic also can go a long way to reducing the environmental impact of your menu. Fossil fuel-based synthetic fertilizers and pesticides account for more than one-third of the energy used on U.S. farms. But organic food can fall short when food miles start entering the equation.

Cool">http://seattletimes.nwsource.com/html/pacificnw/2008016986_footwonders.h... Planet: 7 simple ideas to help solve global warming

From The Independent:

An emergency "Plan B" using the latest technology is needed to save the world from dangerous climate change, according to a poll of leading scientists carried out by The Independent. The collective international failure to curb the growing emissions of carbon dioxide (CO2) in the atmosphere has meant that an alternative to merely curbing emissions may become necessary.

The plan would involve highly controversial proposals to lower global temperatures artificially through daringly ambitious schemes that either reduce sunlight levels by man-made means or take CO2 out of the air. This "geoengineering" approach – including schemes such as fertilising the oceans with iron to stimulate algal blooms – would have been dismissed as a distraction a few years ago but is now being seen by the majority of scientists we surveyed as a viable emergency backup plan that could save the planet from the worst effects of climate change, at least until deep cuts are made in CO2 emissions.

What has worried many of the experts, who include recognised authorities from the world's leading universities and research institutes, as well as a Nobel Laureate, is the failure to curb global greenhouse gas emissions through international agreements, namely the Kyoto Treaty, and recent studies indicating that the Earth's natural carbon "sinks" are becoming less efficient at absorbing man-made CO2 from the atmosphere.

Climate scientists: it's time for 'Plan B'

white stones (bricks) reflecting sunlight

Yes, I'd read of idea to paint roofs white. From the Guardian:

Should we paint the world white to tackle the impact of global warming? Hashem Akbari, a scientist at Lawrence Berkeley National Lab in California thinks so, and is launching a worldwide campaign to brighten up our cities. Turn enough rooftops and roads a whiter shade of pale, he says, and enough extra sunlight will be bounced back into space to cool the planet.

It won't solve the problem of climate change

Paint for victory: new weapon in climate war is brilliant white roofs

Painting your roof white could help slow climate change by reflecting sunlight back into space. So would painting the moon. Wild eco-goose chase or radical thinking?

 

From BBC website:

The biggest ever investigation into "ocean fertilisation" as a climate change fix has brought modest results.

The idea is that putting iron filings in the ocean will stimulate growth of algae, which will absorb CO2 from air.

But scientists on the Lohafex project, which put six tonnes of iron into the Southern Ocean, said little extra carbon dioxide was taken up.
...

Following fertilisation of a 300 sq km patch of ocean, Lohafex, too, saw a burst of algal growth.

But within two weeks, the algae were being eaten by tiny creatures called copepods, which were then in turn eaten by amphipods, a larger type of crustacean.

The net result was that far less carbon dioxide was absorbed and sent to the sea floor than scientists had anticipated.

 

 

also from BBC:

A report for the RSPB, written by the Institute for European Environmental Policy, said that with an effective planning system, the UK could greatly increase onshore wind development without damaging nature conservation.

Ruth Davis, head of climate change policy at the RSPB, said it was in favour of such an expansion because of the "truly terrifying" impact that global warming was increasingly having on birds.

"Left unchecked, climate change threatens many species with extinction," she said.

"Yet that sense of urgency is not translating into actions on the ground to harness the abundant wind energy around us."
...

"We must reduce the many needless delays that beset wind farm developments," Ms Davis said.

"This report shows that if we get it right, the UK can produce huge amounts of clean energy without time-consuming conflicts and harm to our wildlife.

"Get it wrong and people may reject wind power. That would be disastrous.

 

 

I believe Professor Crutzen is on the right track. But, rather than placing chemically active, indiscriminately sized particles in the upper atmosphere, one could place specifically sized reflective particles of chemically inert material in the atmosphere.

Specifically, a particle of say 2 or 3 microns could reflect incoming solar energy which is dominately in the sub 3 micron wavelength range. The earth is cooled by thermal radiation to outer space, dominately in the 3 to 300 micron range. Carbon dioxide interferes with that radiation, trapping the thermal energy near the earth, and hence "global warming". Particles selected with an appropriate diameter could reflect sunlight, but not interfere with earth thermal radiative cooling. If we reflect 2 or 3% of the incoming radiation, there would be a significant coolling effect. Material placed in the upper atmosphere would eventually settle out, so we could tailor the particles (density and thickness) to last say 5 years or so. Side benefits would be beautiful sunsets every night, slightly extended daylight hours, reduced expansion of deserts, and reduced sea level rise.

My estimate of the cost is a few billions of dollars for each one percent reduction of solar flux, a trivial cost compared to the relatively ineffectual approaches of reduced industrial carbon use, wind, solar, nuclear, etc. A few hundred pounds of material taken aloft and released from each commercial airplane flight could deliver the needed material to the upper atomosphere in a year or so. Alternately the material could be taken aloft with inexpensive hydrogen balloons.

With massive effort and expense, we could reduce atmospheric CO2, but we would be missing out on some important benefits. Probably the real benefit is avoidance of a new ice age. Mankind has placed significant carbon dioxide into the atmosphere, and this will probably inhibit the next iceage, due to arrive whenever the sun feels like reducing output. If an iceage were to approach after we reduce CO2 in the atmosphere, there is very little we could do about it (other than increasing atmospheric CO2, something that has taken us a hundred years to accomplish so far). If we take the alternate approach of placing intermediately lived particles in the atmosphere, we could in a few years stop placing the particle to increase the effective solar energy at the earth surface. All around, the particles seem to be a superior approach

press release from the Royal Society:

The future of the Earth could rest on potentially dangerous and unproven geoengineering technologies unless emissions of carbon dioxide can be greatly reduced, the latest Royal Society report has found.

Geoengineering the climate: Science, governance and uncertainty (published today,1st September, by the Royal Society) found that unless future efforts to reduce greenhouse gas emissions are much more successful than they have been so far, additional action in the form of geoengineering will be necessary if we are to cool the planet.  Geoengineering technologies were found to be very likely to be technically possible and some were considered to be potentially useful to augment the continuing efforts to mitigate climate change by reducing emissions.  However, the report identified major uncertainties regarding their effectiveness, costs and environmental impacts.

Professor John Shepherd, who chaired the Royal Society's geoengineering study(2), said, "It is an unpalatable truth that unless we can succeed in greatly reducing  CO2 emissions we are headed for a very uncomfortable and challenging climate future, and geoengineering will be the only option left to limit further temperature increases. Our research found that some geoengineering techniques could have serious unintended and detrimental effects on many people and ecosystems - yet we are still failing to take the only action that will prevent us from having to rely on them.  Geoengineering and its consequences are the price we may have to pay for failure to act on climate change."

The report assesses the two main kinds of geoengineering techniques Carbon Dioxide Removal (CDR) and Solar Radiation Management (SRM).  CDR techniques address the root of the problem rising CO2 and so have fewer uncertainties and risks, as they work to return the Earth to a more normal state.  They are therefore considered preferable to SRM techniques, but none has yet been demonstrated to be effective at an affordable cost, with acceptable environmental impacts, and they only work to reduce temperatures over very long timescales. 

SRM techniques act by reflecting the sun's energy away from Earth, meaning they lower temperatures rapidly, but do not affect CO2 levels.  They therefore fail to address the wider effects of rising CO2, such as ocean acidification, and would need to be deployed for a very long time.  Although they are relatively cheap to deploy, there are considerable uncertainties about their regional consequences, and they only reduce some, but not all, of the effects of climate change, while possibly creating other problems. The report concludes that SRM techniques could be useful if a threshold is reached where action to reduce temperatures must be taken rapidly, but that they are not an alternative to emissions reductions or CDR techniques. 

Professor Shepherd added, "None of the geoengineering technologies so far suggested is a magic bullet, and all have risks and uncertainties associated with them.  It is essential that we strive to cut emissions now, but we must also face the very real possibility that we will fail.  If "Plan B" is to be an option in the future, considerable research and development of the different methods, their environmental impacts and governance issues must be undertaken now.  Used irresponsibly or without regard for possible side effects, geoengineering could have catastrophic consequences similar to those of climate change itself.  We must ensure that a governance framework is in place to prevent this."

Of the CDR techniques assessed, the following were considered to have most useful potential:

  • CO2 capture from ambient air this would be the preferred method of geoengineering, as it effectively reverses the cause of climate change.  At this stage no cost-effective methods have yet been demonstrated and much more research and development is needed.
  • Enhanced weathering this technique, which utilises naturally occurring reactions of CO2 from the air with rocks and minerals, was identified as a prospective longer-term option.  However more research is needed to find cost-effective methods and to understand the wider environmental implications.
  • Land use and afforestation the report found that land use management could and should play a small but significant role in reducing the growth of atmospheric CO2 concentrations.  However the scope for applying this technique would be limited by land use conflicts, and all the competing demands for land must be considered when assessing the potential for afforestation and reforestation.

Should temperatures rise to such a level where more rapid action needs to be taken, the following SRM techniques were considered to have most potential:

  • Stratospheric aerosols these were found to be feasible, and previous volcanic eruptions have effectively provided short-term preliminary case studies of the potential effectiveness of this method.  The cost was assessed as likely to be relatively low and the timescale of action short.  However, there are some serious questions over adverse effects, particularly depletion of stratospheric ozone.
  • Space-based methods these were considered to be a potential SRM technique for long-term use, if the major problems of implementation and maintenance could be solved. At present the techniques remain prohibitively expensive, complex and would be slow to implement.
  • Cloud albedo approaches (eg. cloud ships) the effects would be localised and the impacts on regional weather patterns and ocean currents are of considerable concern but are not well understood.  The feasibility and effectiveness of the technique is uncertain.  A great deal more research would be needed before this technique could be seriously considered.

The following techniques were considered to have lower potential:

  • Biochar (CDR technique) the report identified significant doubts relating to the potential scope, effectiveness and safety of this technique and recommended that substantial research would be required before it could be considered for eligibility for UN carbon credits. 
  • Ocean fertilisation (CDR technique) the report found that this technique had not been proved to be effective and had high potential for unintended and undesirable ecological side effects.
  • Surface albedo approaches (SRM technique, including white roof methods, reflective crops and desert reflectors) these were found to be ineffective, expensive and, in some cases, likely to have serious impacts on local and regional weather patterns.

Stop emitting CO2 or geoengineering could be our only hope

Press release from American Chemical Society:
[quote]"Green" roofs, those increasingly popular urban rooftops covered with plants, could help fight global warming, scientists in Michigan are reporting. The scientists found that replacing traditional roofing materials in an urban area the size of Detroit, with a population of about one-million, with green would be equivalent to eliminating a year's worth of carbon dioxide emitted by 10,000 mid-sized SUVs and trucks. Their study, the first of its kind to examine the ability of green roofs to sequester carbon which may impact climate change, is scheduled for the Oct. 1 issue of ACS' Environmental Science & Technology, a semi-monthly journal.
Kristin Getter and colleagues point out in the new study that green roofs are multi-functional. They reduce heating and air conditioning costs, for instance, and retain and detain stormwater. Researchers knew that green roofs also absorb carbon dioxide, a major greenhouse gas that contributes to global warming, but nobody had measured the impact until now.
The scientists measured carbon levels in plant and soil samples collected from 13 green roofs in Michigan and Maryland over a two-year period. They found that green roofing an urban area of about one million people would capture more than 55,000 tons of carbon, the scientists say. That's an amount "similar to removing more than 10,000 mid-sized SUV or trucks off the road a year," the article notes.
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ARTICLE #1 FOR IMMEDIATE RELEASE
"Carbon Sequestration Potential of Extensive Green Roofs"
DOWNLOAD FULL TEXT ARTICLE http://pubs.acs.org/stoken/presspac/presspac/full/10.1021/es901539x[/quote]