Albedo

[Robert Chris]

Following our discussion a few minutes ago, I've just done a back of the envelope calculation that shows that to deliver a negative forcing of -1Wm^-2, 2.4% of Earth's land surface (an area about the size of India) would need to treated.  This assumes s starting albedo of 0.2 and an increase to 0.8 which is the albedo of pristine snow.

I think we can assume that painting surfaces white or covering them in reflective material is not going to be a plausible way to provide a worthwhile amount of global cooling.  That said, it could provide really worthwhile amounts of local cooling in tropical climates.

It should also be noted that outside of the tropics, painting building roofs white would increase the demand for heating in winter months.  It would also require considerable maintenance everywhere to keep the surfaces clean and fully reflective.  The cost profile is not attractive.

Mirrors at L1 (a spot between Earth and Sun that's about 1 million miles from Earth), crazy at that might seem at first glance, it could well turn out to be by far the most cost-effective option.  Search on 'mirror in space Lagrange L1' and lots of options emerge.

Regards

RobertC

[Robert Chris]

Oops! I hit Send too soon.

I meant to add that mirrors in space might fit the notion of an international albedo accord much more neatly than attempts to engage with large numbers of technologies that are perceived to be marginal in their impact and/or potentially too risky.

It becomes a unified global Moonshot approach with a clear objective and very well defined operational focus.  The big problem will be decisions around who controls the thermostat; but that applies in all albedo options.

Regards

RobertC

[Tom Goreau]

L1 as an optimal site for mirrors is an old idea, going back to Arthur C. Clarke. A lot more feasible now!

 

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[Robin Collins]

H. Akbari at Concordia argues whitening roofs and making roads lighter buys time by reducing summer heat dome effects in cities.

Time we need for other efforts to kick in. 

 It isn’t intended as a mechanism for global cooling, only a contribution to local cooling. 

Robin 

[Sev Clarke]

RobertC, 

Could you not rather calculate the negative forcing resulting from increasing the 70% of remote ocean albedo from 0.06 to 0.12 using Buoyant Flakes, then of using stabilised nanobubbles to increase it by whatever additional albedo is required to reverse global warming? A larger canvas than that of India will be required, and it will probably be better if the cooling is more evenly spread.

If done soon enough, such interventions should also prevent AMOC from slowing, European agriculture from dying, and producing enough oceanic biomass to offset carbon emissions. 

Cheers,

Sev

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[Robert Chris]

Sev, happy to do that but I need to know albedo with nanobubbles.R

Sent from my Galaxy

[Michael MacCracken]

Hi Robert and Chris--If you do this, realize that increasing the albedo under cloud coverage has little effect as clouds reflect the radiation back down, and as light below clouds is diffuse, unlikely to make it back to space. The Earth's albedo is currently about 30%. About 25% of the 30% is from clouds, and only about 5% from the surface. So, if cloud coverage is 50% (I think they are actually a bit more), that would mean the average surface albedo is 10%. If clouds are evenly spread over land and ocean (I think they are more likely over the ocean) and oceans cover 2/3 of the planet and the ocean albedo is currently 6%, then the ocean is contributing 4% to the 10% of surface albedo and land is contributing 6% (so 1/3 times 18% average land surface albedo--so high because of deserts and snow/ice.

So, how much does the ocean albedo have to be increased to affect the global albedo by 1%, say from 30 to 31% (or 29% to 30%)?

Well, albedo equals sum of the cloudy share (say 50% cloud cover times 50% cloud albedo) plus the clear air share (50% times 2/3 times 6% for the ocean plus 50% times 1/3 times 18% for the land)---and counting surface actual albedo as the effective albedo to space is a bit high given there will be absorption of the reflected radiation in the atmosphere.

So, as to the proposed increase from brightish flakes over the whole ocean--something likely hard and expensive to achieve (just take a dollar per kilometer and that is 3 times 10 to the 8th, so $300B divided by fractional lifetime of the flake's reflective effectiveness  if everything is spread perfectly--so actual cost would be in trillions per year) and .5 times .67 time 6% gives 2% increase in albedo, if everything is perfect (including my calculations). And it would not be.

I think hardly realistic.

Best, Mike

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[John Nissen]

Hi Robert,

Because L1 wobbles as the moon circles the Earth, it may be difficult to get the desired cooling effect from space mirrors.  And anyway the main cooling will be around the equator, whereas we have a priority on cooling the poles, because of tipping processes nearing a point of no return.

The temptation of space mirrors will be to postpone SAI, and then it will be too late to prevent tipping-point catastrophe.  However space mirrors would be worth developing as a possible technique to take over from SAI in two or three decades perhaps.

Gernod was asked whether SAI could be weaponised, and he thought not, because the SAI provides a fairly even cooling between latitude of injection and pole due to Brewer-Dobson circulation in the stratosphere.

BTW, I think ships should use bunker oil when away from the coast, to help restore a lot of albedo which seems to have been lost recently; though ideally the sulphur extracted in purification should go into the stratosphere as SO2 to produce even greater cooling!

Cheers, John

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[Robert Chris]

Hi John

As regards L1 wobbling, that's what research is for.  I very much doubt that there are engineering challenges associated with space mirrors that can't be overcome with well-resourced research.  I see your concerns as research questions not as reasons to not proceed.

I'm amused by the notion that space mirrors will be a moral hazard for SAI in the same way that SAI is a MH for emissions reduction.  I have written extensively about this in this group.  MH is nonsense.  It is an imagined problem for which there is zero empirical evidence.  Moreover, if it ever did emerge as a real problem, it could immediately be stopped by policymakers applying regulations to do so.  If they didn't do that for fear of backlash  from vested interests, it would be the policymakers' timidity that would be the problem not the MH.

As to space mirrors being developed as a successor to SAI, what if SAI never happens at sufficient scale and speed?  I think it's very plausible that SAI will not be deployed at the scale and speed necessary to avoid COCAWKI (the collapse of civilisation as we know it).  However much we think it MUST happen, there are many others for whom it MUST NEVER happen, and even more who aren't that interested either way.  My crystal balls are not sufficiently reliable to predict the future role of SAI, so I think it prudent to assume that it might not deliver its potential and we'll need something else.  Why not space mirrors? 

It isn't either/or.  It's both/and.

I also think that COCAWKI is plausible, indeed probably rapidly becoming most likely.  Contemplating COCAWKI requires a different mindset.  Almost no one is yet focussing on that.  Perhaps a few preppers are.  And Jem Bendell!

Regards

RobertC

[Paul Gambill]

IMO, from talking with the Planetary Sunshade Foundation folks, I really like the sunshade/space mirror concept. It is far more elegant than SAI, and while it introduces different types of risks, I like that it can offer reflection without many of the downsides of aerosol deployment. Unfortunately I think most of the SRM research field has viewed a sunshade concept as more sci-fi than even their own work, so it hasn't gotten a lot of attention. There is a conference coming up next month in the UK about this.

If in the proverbial napkin diagram SAI is the temporary intervention to peak shave, then with a sunshade it could go like this recursively:

1. Begin SAI
2. A sunshade isn't plausible until the second half of the 21st century, so once it starts getting deployed, then you can wind down SAI
3. Then wind down the sunshade as albedo normalizes and GHG levels are restored to pre-industrial levels

With a sunshade, we might need SAI for only a few decades, instead of potentially centuries. But that's as far as my knowledge goes on this, and I am looking forward to learning more at that workshop!

Paul

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Paul Gambill

Inevitable & Obvious

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[Sev Clarke]

Hi Mike,

Whilst your point about cloud reflectiveness reducing the albedo effect of brightening the ocean surface is well understood, you seem to have a mistaken idea about Buoyant Flakes. The main effect of the flakes is not their own brightening, but that of ocean brightening caused by the ultra-slow release of FePSi and trace elements released into the surface waters by them over the year or so they are expected to last on the surface as they nutriate phytoplankton and seaweed. Each square metre of treated, oligotrophic surface water might only have a couple of flakes on it on average, representing 0.005% of the ocean surface area, such is the likely effectiveness of ocean iron supplementation by buoyant flake. Nor would spreading need to be perfect, as flake plumes would tend to be further dispersed by current, wind and wave.

Some 130Mt/yr of rice husk is produced, of which 100Mt might be available for Buoyant Flake production. In turn, this might be made into some 700Mt/yr of flake for dissemination from bulk shipping. This is less than the 958Mt/yr of iron ore and concentrate that Australia produced, most of which was shipped to our East Asian markets. At an average of US$8.0 per wet tonne delivered to China, the running cost of this is only some US$7.7b/yr. Hence, an estimate of flake delivery cost to global oceans by cheap, obsolete bulk shipping from the eight suggested flake factories around the world would be only about US$5.6b/yr, not trillions. Nor would there be much need for empty backloading, as there is with the iron ore trade. Hence, it is an entirely realistic proposition. Indeed, it would likely be a profitable undertaking, given the likely increase in fishing royalties and other potential income streams from the endeavour.

Best, Sev

[Michael MacCracken]

Hi Sev--Thanks for the explanation.

Of such proposals in the past, there has been, I think, concern about transferring all those needed soil nutrients to the ocean and so depleting soil fertility on which agriculture depends. Is that an issue of concern when done over an extended period?

Mike

[Sev Clarke]

Hi Mike,

Happily, it is not. There are more than enough of the needed minerals in finely-divided, readily and cheaply accessible wastes and non-commercial ore sources to provide FePSi and trace elements for marine phytoplankton and seaweed for many decades. And the active nitrogenous material is made by iron-fertilized diazotrophs, some actually being symbionts of diatoms.

The iron can be from either red mud or non-commercial grades of iron ore.

The opaline silica as a waste product from annual rice husk production.

The phosphate and trace elements from the phosphatic clay wastes left over from P extraction.

And once the ocean has been restored to pre-industrial productivity or better, most of the supplementary nutrients will become almost endlessly recyclable - helped by whales and krill.

There should be no fear of soil fertility depletion from this activity. Indeed, we should be able to draw from the sea seaweed and biomass to aid soil fertility.

Sev

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[Tom Goreau]

It’s very risky to overfertilize the ocean because it causes dead zones!

 

Biogeochemical feedbacks link terrestrial and ocean storage and greatly affect long term CO2 content, especially through limestone production and dissolution.

 

A recent paper shows that the rise of land plants changed the carbon/phosphorus ratios of the ocean as carbon storage shifted from the ocean to land, which we are now shifting back.

 

 

 

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[Michael MacCracken]

Hi Sev--It would be really interesting to see how a model reacts to a doubling of the ocean albedo everywhere (or perhaps just over some latitude bands of the ocean)--or just a 50% increase--phased in over, say, five years. Has such a modeling experiment been done with a full global model that would allow the full set of interactions--it would seem quite a simple change to program in?

I think Elizabeth Barnes and her group at CSU did sort of a related experiment by doing just a little SAI everywhere and the result first evident was a slowing of the hydrologic cycle, so less evaporation, etc.  

Mike

[Sev Clarke]

Yes, that is why the ultra-slow release over a year of the needed supplementary nutrients from Buoyant Flakes is much to be preferred to using soluble ferrous sulphate. Similarly, the use of nutrient-supplemented diazotrophs to generate reactive nitrogen fertiliser for the ocean is much to be preferred over adding soluble nitrate fertiliser. And as the phosphate in phosphatic clay wastes is tightly bound to insoluble minerals, it too releases slowly, made slower by the fact that only the slowly-degrading surface of intransigent and lignin-rich Buoyant Flake is exposed to UV rays, seawater and the marine ligands designed to make phosphate available to phytoplankton.

Sev

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[Sev Clarke]

Hi Mike,

Yes, I have made several attempts to interest modelling groups in running a model with similar conditions - so far without uptake. Such ought to be feasible using only a relatively simple model and coarse settings. Still no dice. Hopefully, RobertC’s model might provide some useful results, even though it is not strictly an Earth System model.

Have you warm contact with any ES modeller who might be prepared to run such a model and seek to have published its results?

My surmise is that increasing ocean albedo at low and middle latitudes would have little effect on the strength of the hydrological cycle, but might well reduce the damaging severity of its fluctuations - caused in part by the increase in DMS emissions.

Cheers,

Sev

[Tom Goreau]

This might be usefully combined with essential trace element supplementation, such as those in Nualgi that stimulate diatoms specifically.

 

Are you working with Bhaskar? I’m trying to set up local tests to use Nualgi in sewage contaminated river basins in Cambridge, Massachusetts, to shift to diatoms and fish instead of cyanobacteria and dead zones…..