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It is an interesting solution especially if we have to stop an positive feedback of CH4 but so far, only one team has modeled this kind of stratospheric albedo modification, and with few inputs.

But this solution will make the planet, a drug addict, if we implement it without drastically reducing the causes of the problems.Any interruption (war/economic/politic whatever) of the process would lead to a catastrophic increase in temperature (specially if we continue to improve our technology an therefore reducing the solar dimming).

by fredouil (fredouil@gmailgmailgmail.com) on Thu Oct 12th, 2006 at 10:05:42 PM EST
This is the drug-addict's solution to the side-effects of drug use.  

Designed to enable MORE drug use.  

Incidently, that SO2 won't stay in the stratosphere forever.  Where does it go?  What happens THEN?  

While I do think volcanos are wonderful, by what stretch of the imagination are they benign?  

The Fates are kind.

by Gaianne on Thu Oct 12th, 2006 at 10:46:08 PM EST
[ Parent ]
Incidently, that SO2 won't stay in the stratosphere forever.  Where does it go?  What happens THEN?

You are entirely right, and you ask basic and important questions that must be addressed.

For particle lifetimes in the stratosphere, please see diary section 2, paragraph 1.
(Lifetime before returning to the ground: roughly 2 years)

For the effects of particles leaving the stratosphere, please see diary section 3, paragraph 3.
(Effect: about a year's setback in ongoing global SO2 emission reduction, which is currently few percent per year.)

Words and ideas I offer here may be used freely and without attribution.

by technopolitical on Fri Oct 13th, 2006 at 02:11:30 AM EST
[ Parent ]
A more complete analogy would be to a patient with a chronic, worsening disease who takes a drug that alleviates many of the symptoms, but doesn't treat the cause. Stopping the drug lets the symptoms return.

To extend the analogy, however, there would be something costly and difficult that the patient could do to slow or arrest the worsening of the disease -- which the patient would be less likely to do if the symptoms were lessened.

Also, since natural systems typically respond better to slow changes than to fast ones, the analogy would have to include nasty effects caused by sudden withdrawal of the drug.

To round out the analogy, the symptoms must themselves cause cumulative harm, which the drug prevents. Here, I'm thinking of effects like progressive melting of icecaps.

----------------

Regarding interruptions, if the cost is only 1/5000th or less of GWP, South Korea or the Netherlands could do it themselves.

Words and ideas I offer here may be used freely and without attribution.

by technopolitical on Fri Oct 13th, 2006 at 02:00:43 AM EST
[ Parent ]
If a temporary SO2 sunscreen can reduce global temperature the way Pinataubo did, great.  And probably using coal-fired plants to do it, as Migeru suggests, would be to rely on technology already in place. But the expense of modifying scrubbers to permit SO2 release will not be undertaken voluntarily by utilities.

In any case, we also must mitigate CO2 on a large scale.  There is a limit to how much carbon dioxide forests, deserts, and soils and can take up before they start expelling CO2 into the atmosphere.  

Forgive me for repeating a comment I posted on Techno's Ocean Acidification diary:

The ocean is a tremendous carbon sink.

Oceanographers I've talked to are thinking that the changes in ocean temperature are too rapid for many species to adapt.  The acidification rate of the ocean may also be too rapid for adaptation of species.

At present carbon emissions from human activities continue to increase at a steep rate.  

Meanwhile, the increase in ocean temperature is speeding up the chemical processes of acidification.  This is ultimately bad news for critters with exoskeletons. And for the food chain.  One billion people rely on the ocean for food.

If the present acidification due to carbon absorption continues at the present rate, erosion from terrestrial rock will not supply enough buffering to counter the acidification.  At some point the ocean will fail as a carbon sink.  So the carbon will remain mostly in the atmosphere, creating a rather Venusian environment.

In this scenario, there's a tipping point that will be catastrophic unless drastic reduction of carbon emissions are undertaken.

by Plan9 on Sat Oct 14th, 2006 at 10:16:53 AM EST
[ Parent ]
Modifying coal power plants is easy:  The scrubber that removes SO2 by reacting it with lime doesn't remove anything else of note, so you just take it out.  The problem is that you don't want SO2 in the lower atmosphere.  It doesn't stay there, instead it causes smog and gets washed out as acid rain.  Bad idea.

Neither forests, deserts nor soils are carbon sinks, only (very limited) carbon stores.  To remove CO2 from the atmosphere, you have to create organic matter and then bury it.  As a first step in that direction, do not use recycled paper.  Making paper and burying it in landfills is the only human-caused process that puts carbon back into the earth.

Earth will never become comparable to venus.  Our oversized moon prevents earth from accumulating such a thick atmosphere.  Also, please try to stay reasonable.  We're talking about 380ppm CO2 on earth while venus has 965000ppm CO2.

by ustenzel on Sat Oct 14th, 2006 at 06:09:52 PM EST
[ Parent ]
Good points all.  Thanks.

The Venusian reference was irresistible, but, as you say, an exaggeration.

by Plan9 on Sun Oct 15th, 2006 at 12:07:03 AM EST
[ Parent ]
To remain in the metaphor, a diabetic is a kind of "drug addict". And I also believe there is a valid medical and social case to be made for drug maintenance programs for certain addiction profiles as a last resort.

I don't know enough to either endorse or reject the sunscreen idea. At first sight, I find it unpalatable.

But I fear that responding to global warming is going to mean choosing the least ugly of a whole range of unpalatable options.

The fact is that what we're experiencing right now is a top-down disaster. -Paul Krugman

by dvx (dvx.clt št gmail dotcom) on Fri Oct 13th, 2006 at 04:36:07 AM EST
[ Parent ]
"Unpalatable." A good description.

It becomes somewhat more palatable, though, if it's a bridge to a better answer. I expect that projections of ongoing, large CO2 emissions will turn out to be pessimistic because falling costs for solar-energy based electric power and fuels will provide an attractive alternative to burning stuff. At that point, political pressure should be very effective at forcing a switchover.

If solar energy gets cheap enough, as I expect, then we can start thinking about removing surplus CO2 from the atmosphere. Extracting it would require a lot of energy, but not completely overwhelming -- a fraction of human power consumption in 2006 over a fraction of a century.

Words and ideas I offer here may be used freely and without attribution.

by technopolitical on Fri Oct 13th, 2006 at 02:59:18 PM EST
[ Parent ]
BTW the Sunscreen concept must by its nature reduce the efficacy of solar panels...  to the same extent that it is efficacious in preventing solar radiation from getting inside the atmosphere.

The difference between theory and practise in practise ...
by DeAnander (de_at_daclarke_dot_org) on Sun Oct 15th, 2006 at 12:33:34 AM EST
[ Parent ]
Not necessarily, since there isn't simply "radiation".  SO2 might preferentially reflect wavelengths that are useless for solar panels.  This isn't all that unlikely, since solar panels use quite a narrow part of the spectrum anyway.  (But I don't have exact data to prove this either way.)
by ustenzel on Sun Oct 15th, 2006 at 05:53:00 AM EST
[ Parent ]
Yes, give or take different effects at different wavelengths. As you note elsewhere, reduced sunlight is also an issue for agriculture. A key question is the size of this effect relative to other sources of variability.

This NREL map of mean annual PV solar radiation indicates that, at equal latitudes across the southern U.S., the energy available for photovoltaic systems varies by something like 40% because of variations in clouds, haze, and so forth. Photosynthesis should see a similar variation.

A rough estimate of the reduction in sunlight needed to offset warming of 1°C can be made by noting that 1°C is about 1/300 of the absolute temperature. Because of the T^4 scaling of thermal radiation with temperature, this is equivalent (keeping albedo and thermal emissivity constant) to a change of about 4/300 in the input and output radiated power -- about 1.3%. From a photovoltaic power perspective, this would be equivalent to reducing PV cells from (for example) 30% to 29.6% efficiency.

From this rough calculation, it seems that weather variability is a much larger effect.

Words and ideas I offer here may be used freely and without attribution.

by technopolitical on Tue Oct 17th, 2006 at 02:06:11 AM EST
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