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| 00:00 | yep okay so we're going live now hello and good afternoon and let me welcome you all to the workshop number three on refreezing the arctic and we're going to be looking at marine cloud brightening and other techniques for achieving this just a couple of instructions please submit questions at any time using the zoom q a function please only the q a function if you want to chat that's fine but questions will only be looked at from the q a function and could i also ask that the speakers don't be tempted to reply to |
| 00:52 | the zoom q a because that tends to lose the question so i will select from amongst the questions that come in the questions that i will read out so you can also ask questions via your youtube chat or via twitter and there i leave the speakers to respond as they wish this session is being live streamed and recorded and the recording will be shared on our youtube channel afterwards and with that let me just give you a brief introduction to the center for climate repair at cambridge we have set up the center which is |
| 01:34 | focused on four objectives all represented on this slide first and foremost we need to re reduce we need to have deep and rapid emissions reduction secondly we need remove we need greenhouse gas removal at scale and that at scale means to bring the greenhouse gas levels in the atmosphere down very significantly from where they are today and thirdly repairing the damaged climate systems is referring to the climate systems that have gone past their tipping point and we believe the arctic circle represents the key case of a climate system that |
| 02:18 | has gone past its tipping point hence this series on uh dealing with the business of trying to re-freeze the arctic region we also have a fourth objective which is really my big focus to see that there's an agile international political and financial action to deliver all of these processes we have i believe five years now to put everything in place and to act on those things we put in place to manage the future of mankind for the next few millennia the next slide shows us the series that we've just coming to an |
| 03:06 | end with today's meeting we had a meeting on a series of meetings on greenhouse gas removal looking at the ethics and governance nature-based and hybrid solutions technological and hybrid solutions and then climate repair we began this process of looking at methods of refreezing the arctic starting with the state of the arctic we then looked at stratospheric aerosol injection and other techniques and then marine cloud brightening and other techniques today so i'm delighted to tell you that once again we have got a superb list of people to |
| 03:45 | give us their views of what needs to be done and what they are themselves doing and these are the four speakers we have today uh professor peter wadhams unfortunately has fallen ill over the weekend and is unable to be with us but i'm very pleased to say that our deputy director who hunt has stepped into the breach and will give us a lecture on marine cloud brightening some practical issues that we are currently dealing with so let me then move on and suggest that we turn to our first invited speaker and the first invited |
| 04:30 | speaker is alan guardian oh yeah alan alan i've got your biography in front of me here you obtained your phd in the department of meteorology imperial college you're and professor of uh dynamic meteorology at the university of leeds you've co-authored with john latham more than 10 peer-reviewed publications on modelling the implacs applying marine cloud brightening to lessen the current rapid global warming caused by greenhouse gas emissions alan could i turn to you to give us a little 15 minute outline of what we've been |
| 05:24 | doing thank you david thank you very much and for all of you for inviting me to give the opportunity to talk about marine cloud planning i've been working on this with john latham for many years now and if i could have the first slide please uh can you i can't see the first slide yeah it's coming ellen oh he's coming thank you so so the idea is really john latham's idea that by injecting a sea salt aerosol into into marine stratic luminous you we can reduce the uh the albedo increased the albedo of the planet and |
| 06:09 | reduced the warming this idea it first came out from some work by john laisman nature paper and um in uh and it followed on from the work of slingo who uh spent many years looking at that marine cloud the effects of reflects of strata cumulus cloud so here's the first slide basically many contributors unfortunately john latham died recently uh well i'm just going to give you a brief talk on marine cloud brightening and some of the impacts next slide please katie so you've there's many of these plots |
| 06:49 | are available the left-hand one i don't actually agree with the dates and timings but it shows the uh left-hand panel if what we're looking at i think probably if we leave it alone we'll be up to well above five degrees c by 2100 if you look at the right hand upper panel you can see the latest pyromast arctic sea ice volume which which again shows the danger of the arctic removal and we had a very good session on that recently and finally the bottom panel shows the later stephen salters design next slide please so here |
| 07:26 | where i took part in the vocals project in 2008 and in the middle panel there you'll see the stratocumulus which is over over space of several hours in and a little yellow blob is where there was a ship so start cumulus cover 30 percent of the oceans strata humans have a high reflectance which depends on the droplet number and the mean droplet size and if you look at the right hand panel you'll see an example of of stephen salter's classic example of the difference between having a certain volume of glass |
| 08:00 | speeds on the right hand glass speed is much wider than the left hand set of glass speeds and that is just because of that size of the particles so let's have a look at this stratocumulus in more detail next slide please so here is uh this came from paper the tumi effect 1974 it produced this classic paper on the bottom on the bottom panel there we've got fewer large drops produce a lower albedo more smaller drops produce a higher albedo and this came from the latham 1990 paper many people would argue that we've |
| 08:41 | actually been changing the nature of starter humerus clouds with global warming but that's a completely separate issue this is the tomb effect this is the basic next slide please so here is a classic photograph you might not recognize it but if you look to the right you can see the outline of france the bay of biscay and you have a rectangular box here and if you look at the optical thickness that's the bottom left and look at the effective radius particle size bottom right you can see that the most yellow area in the bottom right panel |
| 09:16 | corresponds to the whitest area from the satellite image and what we have here is a series of ship tracks crossing crossing the ocean and producing the whiter bands ship tax do indicate the effect of marine cloud brightness the problem is they ship tracks are usually various aerosol size so they can produce uh lessening of the of the reflectance later on next slide please so what are we talking about well for a cloud physicist like me you can see the this eight can mode the accumulation mode and you can see what's called sometimes |
| 09:57 | called the green field gap and this client comes from stephen salter and this is gap here is where a lot of particles are staff scavenge and hence there's a dip in the number concentration and i'm proposing that we should look at inject particles of maybe 200 nanometers size to produce the brightness the next slide please so the first big challenge and the two points from this side is what is the optimal radius and this is going to differ depending on the geographical locations geographical locations have slightly different structured |
| 10:33 | stratocumulus clouds and i'm suggesting that we need to have more high resolution numerical simulations and to complete this regime so the current theory which i think is probably reasonably well represented is the paper by ultrascar and i've given a reference for that wood has come out with a very recent paper it's in review of suggesting a smaller size is optimal i don't think i agree with that figure at the moment and i'm going to show you the reasons why in the next slide please so this is some work carried out by |
| 11:13 | muric andre chuck and he he worked with the next slide please and he worked with uh with rayner and several cloud physicists and he's produced a series of papers now in cloud physics we have bulk models we have bin models and this is a particle model and i think it's probably the one i prefer bin models can be quite diffusive but we can talk about numerics all day but that isn't the point what we did here is just two plots on the left and the right and their vertical velocity plots underneath stratocumulus cloud |
| 11:50 | which has about a kilometer a thousand meters high and you can see on the left-hand plot there's lots more blues and uh purples and on the right hand side there's lots more greens so the greens sorry about the color coding at the top because the yellows haven't come out though greens are small particle size so we've taken the stratocumulus we observed and we injected i've only given two that's low medium and high and we injected spray into it there's a lot in here i could talk about but all i want to point out is the |
| 12:29 | takeaway message is the right hand plot where we inject with high with with a high concentration then you get lots of green that means it's reflection next slide please we can represent this in a different way the two columns there we've got the left-hand plots they're the albedo and the right-hand plots we've got a representation that you saw the same colors as last time uh the the the particle sizes so let's just take the left hand plots here we've got a b and c so we've got high medium and low aerosol distribution and |
| 13:10 | they represent the uh with the they represent the sensitivity so if you look at the top of the left block you can see that when there is high aerosol loading in the stratocumulus cloud seeding doesn't make much difference so what you we've got there is a standard deviation in gray so it doesn't make much difference when if you look at the lower left-hand plot where there's lower uh lower concentration you can see that seeding has a significant effect it increases the albedo by 10 more 20 and in there of course there's the |
| 13:49 | reference run so i don't want to go into any details there but what i'm saying is here we've got the representation of what we showed in the previous pretty picture if you look down the right hand side you can see that the number concentration indeed is much higher in the top case than done than in the other examples and the number concentration the low case that's the bottom right is significantly higher it's it's it's more than double the case so in the low low aerosol number cases where you've got a standard |
| 14:29 | stratocumulus inserting this these these small aerosol sprays from from some source of the surface or whatever produces a significant effect and next slide please the paper all the references are there so now i'm going to move on to the second part of the modeling which is the global scale modeling and again there's a few references you can look at it afterwards next slide please so this is a technical slide about the details of the high gem climate model i think it's useful to put in there basically it's a |
| 15:04 | relatively low resolution well uh in my opinion but it's considered high resolution and the model was run we increased by one percent for year the co2 to 2045 to double the industrial and then we just let the model run stably from 270 20 70 to 2090. and i'm going to show you some results to look at as examples the impacts i'm going to show look at the hurricane development and i'm going to look we shall interest daniel some of the work done on the coal bleaching next slide please so that's a rather technical slide and |
| 15:43 | this is the two experiments we carried out if you look at the green blobs this is the three most populous regions where you get stratocumulus and that's why they were chosen they were chosen by andy jones originally with john latham so we those represent five percent of the maritime uh surface there also represent the areas where there's most uh most stratic humorous clouds the lower right and block is represents the area where we decided to try and see what would happen if we seeded the whole ocean however let's continue on that now |
| 16:21 | next slide please so here what areas were seeded for how long so this is remember those if you look at the lower right-hand block we seeded at 375 per cubic centimeter and you can see the effect is most strong denoted of minus 40 watts per meter squared over the regions where we see it in the stratocumulus you can see the effects globally because we're looking at a global system the upper right panel is just a brief guideline to remember what we did up to 24 45 co2 increase and then let it and then let it just settle down next slide |
| 17:03 | please so this is the first um impact hurricane weakening uh so what does it look like next slide please so here uh is part of the atlantic ocean and the upper left-hand plot don't worry too much about the details is what is the sea surface temperatures between two co2 and one co2 and we get some we get the impression that the sea is going to be a lot warmer remember that the the intensity of hurricanes depends on the sea surface temperature when it's above approximately 26 and a half degrees celsius you get hurricanes as |
| 17:45 | you get warmer as emmanuel showed you get more intense intense hurricanes the bottom right hand plot there shows what is the effect of when we just seed the three areas and obviously this area these two the area of namibia and the area of the southwest uh southern america shows the biggest impact there and the message to take away all i'm trying to say here is this is an example you can look at it in the in in the paper but essentially i've talked about temperature and precipitation in in the lower panel you can see the |
| 18:23 | effect on temperatures next slide please uh next slide please so let's now look at the the coal bleaching idea that daniel's going to talk about in a few minutes so what have we got here sorry that the color scale is different the color scaled here is different but it's the same image we've got the gulf of mexico we've got the middle of the pacific and we've got the oceanic reefs off the uh the three areas that we're looking at the coal east and you can see that there is significant warming |
| 18:59 | now when we do 2c co2 and mcb then look the the as you can expect the area of of cooling is the strongest over those three areas that we've seeded but it has an effect on the those three regions that we're going to look at and i'm going to ask for the next slide because just focus on the bottom slide which i have a panel which i've repeated and here we've got some difference the difference between two co2 and control is off the order and a half degree celsius when you put the mcb in those three regions |
| 19:37 | you can actually reduce it now cold bleaching is rather complicated it depends on the peaks not necessarily the warming periods but anyway this shows that it has an effect and you can look at this paper if we decided to uh seed all over the globe then we get a big reduction in temperature but whether that's feasible or not i don't think we should do it anyway but anyway it shows the effect a significant cooling of the planet next slide please so now what what is the atmosphere doing and this really is uh it's driving the system next slide |
| 20:18 | please and so this is in fact my last scientific slide really this shows what is the effect now the atmosphere works as a as a conduit hot equator cold pole so if we look at the red and the blue curves they're almost on top of each other and that is the mcb with three regions and the can and the control and they overlap each other completely if we just do the two co2 the two co2 is the green curve the upper green curve and that shows that we're actually transferring heat from the equator to the pole and this is that this is what's causing |
| 20:58 | my opinion the melting of the ice if we then globally seeded then uh you'd have the uh in the uk you'd have the ice coming down to the north of scotland in an ice age so that's a bottom turn next slide please so this is the final the final idea is coding manipulation which is next slide please stephen sold us so if we divide no no the previous side thank you upper right plot we divided the globe into 89 set internet sections we turned the seeding off for 10 days we thought two days was too short 10 days was about right |
| 21:39 | and the bottom right shows that some areas have bigger effect than other house which we expected we expected the namibia and uh and the south west pacific next slide please so here this is the last picture i'm going to show shows that if we take two regions just take two regions just consider precipitation the northern amazon and the southern amazon southern amazons on the left what areas would affect the precipitation in those regions the most and this is the seeding pattern in fact the increased rainfall overall |
| 22:17 | in southern amazon if we looked at the northern amazon the right-hand blob right on picture you can see there's some blue blobs where seeding would reduce the amazon precipitation this this idea of coat where you could seed what is the impact on certain regions can be investigated and uh to try and minimize side effects next slide please so what have i done in the talk this is a summary i've presented some background information on marine cloud brightening i've presented some papers i'm afraid mainly mine but there's a lot more out |
| 22:52 | there i showed some high resolution model simulations and i've represented some results and impacts of the global climate model simulations and finally the coded manipulation could be used to try and minimize side effects because there will be side effects however the side effects of minimize minimize also that the huge effect that double co2 will have on precipitation over the globe conclusions need to optimize the size of ccn and we need more simulations thank you very much david thank you very much katie can you hear me uh right so |
| 23:48 | basically i've got a couple of questions have come in and the first thing is to emphasize that everything you've presented to us is is modeling and uh so i i just have my own little question the reliability of models do you have checks on reliability um i i i use models all the time and i find them very unreliable i i think we should and i think i think brian hoskins would agree with that he was also a model i've now done some work with two kilometer modeling was and i think that's much better which |
| 24:25 | shows that but the the the idea is i think in principle the models are quite good i think they're very good for temperature surprisingly i don't think they're very good for precipitation the models need to be improving but so far the models have been have been reasonable they've been predicting the right sort of trend the models of ice destruction have been catastrophically bad so the loss of the arctic ice was predicted if you look at all the the iccp reports they totally underestimate it and i've i've talked with people at |
| 25:01 | ecmwf about it and they agree that even their daily forecast models nice so for the numerics and the modeling for the global scales inadequate but i think they have the right trends thank you very much i've got a a question from hans van der lu who says is minus 0.04 degrees centigrade to minus 0. |
| 25:27 | 58 degrees centigrade taken from your modelling enough to make a material difference to impact arctic melting um i i i i showed the picture of the meridional heat transfer and that is so you've got numerous papers julius lingo lots of paper that is the critical role of the atmosphere is to remove heat from the equator to the pole so you might be dealing with small temperatures but you're the amount of advection is huge so the oceanic transport is very slow it's the atmospheric transport and i think that all the results that they're |
| 26:10 | consistent that even such small temperature differences in the air mass of course the the latent heat release is phenomenally important one could argue that the greenland is being heated up by latent heat with a release of energy there's lots more moisture there than than the temperature i'm not going to argue with that or one way or another but the temperature is a guide latent heat moisture flux is are huge with meandering jet streams they're taking all this warm moist air to the arctic alan thank you very much i |
| 26:48 | i'm going to ask you to stay in for the q a that will follow all four speakers and now turn to dr daniel harrison daniel is a senior lecturer in the faculty of science and engineering at southern cross university australia he completed his bachelor of engineering civil masters in engineering oceanography and phd biological oceanography at the university of sydney and he is a visiting scholar he was a visiting scholar at the university of southern california where he helped to develop tools to improve the use of |
| 27:24 | oceanographic data in ecosystem-based management of fisheries resources he in 2017 was awarded a prestigious maya innovation fellowship to develop the concept of using solar radiation management approaches for bleaching protection on the great barrier reef in 2019 daniel joined southern cross university as senior lecturer and was appointed sub-program lead of the cooling and shading sub-program within the reef restoration and adaptation program and it's this work that dan is going to give us a talk on dan over to you |
| 28:11 | thank you david for that uh very detailed introduction i'll just um share the screen here and hopefully all goes well oops oh you did except i wasn't at the start of the show there you go got a very quick preview there in backwards order okay so thank you very much for this this work i'm going to present is obviously been contributed to a lot of people besides myself we've been working on this now for a few years since that fellowship in 2017 really and one thing i just really wanted to say at the outset of this talk is that |
| 28:50 | it's far too much work to summarize in 15 minutes so i've had to make the decision to really focus on the technical aspects for this talk we're doing a lot of work into everything from social science to working with traditional owners about these technologies to incorporate their views into the research program uh right through to looking at environmental risks and all those kind of things but necessarily i've had to make this short and i've chosen to focus on the technical aspects so as you're probably well aware the |
| 29:25 | great barrier reef has really been suffering the last few years in the last five years we've had three mass bleaching events which is is completely unheard of before so we had on the great barrier reef some previous bleaching events quite minor associated with el nino years back in 1998 and 2004 but but fairly minor localized bleaching events these last three events which have come almost back to back in 2016 2017 were back-to-back uh over that time as you can see in this slide we've had nearly the whole reef |
| 30:02 | affected that's over 2 000 kilometers from the north to the south and and in fact it would would be a lot worse except that during two of those bleaching events uh cyclones actually came and mixed up cold water and increased cloud cover and helped to reduce some of the severity but even with that stroke of luck in some sense although the cyclones also cause a lot of damage when they do impact directly itching and associated die-offs of the coral and so if we look to the future this is just a plot of the global mean surface temperature of the |
| 30:40 | world and of course we all know it's been been rising uh since the industrial revolution and the associated greenhouse gas emissions i've marked on there in orange the the two relatively minor bleaching events uh historic and the three mass bleaching events there in red arrows that we've had recently and if we just take a very very simple linear fit to this curve which you can see there with the green dashed line and we and we predict that forward those bleaching events occurred during slightly anomalously |
| 31:14 | high global temperatures mostly associated with the el nino cycle but in 10 years time those those high temperatures that we experience briefly will be the global average temperature and if we have an el nino event in 10 years time it might look something like that if we push that out to the optimistic goal of paris of a 1. |
| 31:36 | 5 degree temperature increase globally and then we had an el nino event that might look like that we go all the way up to two degrees which is i'd argue still quite optimistic that's where we are and so you don't need a complicated model i don't think although we we do have some and i'll show you some results from some later uh complex ecological models of the great barrier reef but in my opinion this simple plot here tells the story of the future of the great barrier reef without intervention |
| 32:06 | and and even with really strong action on on carbon emissions now uh the reef's still going to be in a lot of trouble but a hint of what might be possible in terms of cloud brightening comes from this somewhat older um modeling paper here where the authors looked at the sensitivity globally of clouds to marine cloud brightening and while they didn't necessarily find that the most sensitive clouds or the very best clouds for cloud brightening were present over the reef this particular plot uh shows the net average global forcing |
| 32:41 | from cloud brightening uh applied over all of the world's oceans so a scenario that alan talked about earlier but um but didn't necessarily show us the the results from he concentrated on results where where just the best regions were seated and the interesting thing about this spot is that the great barrier reef there in the northeastern side of australia um actually happens to be what in one of the areas that that responded in terms of radiative forcing quite well to this sort of uniform imposition of cloud brightening |
| 33:09 | and and so that was one of the very early bits of evidence i think that i found that the cloud brightening could potentially be useful over the reef so if we look at this a little bit more closely what evidence what what prerequisites i should say do we need um for cloud brightening to potentially be useful over the reef well we need clouds the concept of cloud brightening uh requires clouds to alter it's not making new clouds which is an important aspect to understand um and and because we're we're seeking |
| 33:41 | to alter clouds which have a net uh negative radio forcing on the on the earth a cooling effect um and also because we we hope to reach these clouds by introducing particles down to the planetary boundary layer uh we need low boundary layer associated cloud and for the those clouds to have the potential to respond to cloud brightening to these extra cloud condensation nuclei that we're going to feed them um we need there to be low existing background concentrations of cloud condensation nuclei uh as the the exist as the the |
| 34:15 | concentration of cloud droplets go up um the potential for increasing the albedo decreases exponentially so the first 100 extra cloud particles you can create or cloud droplet concentration you can create gives you the most albedo increase the next hundred only half that or something the the next hundred after that a quarter so if there's already uh reasonable background concentrations of ccn particles it's very hard to make a difference and the final thing that we need for this to work on the reef is we need |
| 34:48 | because we're considering here not a very large scale continuous application of cloud brightening what we're actually looking in these scenarios i'll present is a reactive cloud brightening so a limited area just immediately over the top of the great barrier reef some 0. |
| 35:08 | 7 percent of the earth's surface uh for a limited amount of time in response to an acute heating event such as a marine heat wave which has caused these mass bleaching events so the idea here is is not large scale continuous cloud brightening but quick and agile reactive cloud brightening for probably a period of a few months or so over one of those marine heat waves to to try and relieve the stress on the coral reef and so for that to work that that sort of limited uh application in in both both sort of um spatial area and also in time um you need the hydro dynamics |
| 35:47 | to also be compatible so we happen to have that on the reef because the the reef is is quite shallow and the water has a fairly high residence time there so it gives us the opportunity to potentially cool it down in a limited amount of time or rather i should say more accurately to prevent it heating up as much as it otherwise would have and so if we just quickly go through a few of these prerequisites um some analysis shows that actually despite um what a lot of people probably first thought there is a fair bit of |
| 36:21 | low cloud fraction over the great barrier reef and even during an el nino year where there's substantially less than normal um that these four plots or eight plots divided into two years are over those two mass bleaching events that we've modeled so far and you can see that that although in some cases like february in in 2016 there um there was very low cloud cover over parts of the reef and that is associated with that mass bleaching event because corals are bleached from both a um from being too warm in the presence of |
| 36:57 | of high light energy so you can help to prevent coral bleaching either by lowering the amount of light energy or lowering the temperature and of course cloud writing has the potential to do a bit of both and also if you look at the global model there in the top right corner that also predicts a reasonable fraction of low cloud cover over the reef next the existing uh concentration of cloud condensation nuclei um it's quite fortuitous for this idea that uh during summer when the coral is at risk of bleaching the trade winds bring |
| 37:34 | quite um very clean air from quite remote areas of the subtropical south pacific in over the reef predominantly and that air happens to have some of the lowest background cloud condensation nuclei concentrations anywhere on the world sort of outside of the poles and this translates to low droplet concentrations background concentrations in the clouds over the reef which are shown in those right panels from satellite retrievals so the key questions then for the technical feasibility of cloud brightening given that we think um most or maybe all |
| 38:10 | of the prerequisites have been met uh are the clouds over the gbr then are they actually susceptible to these extra cloud condensation nuclei the prerequisites are met so we believe that they should be susceptible but but are they and what is their sensitivity what cloud condensation nuclei sizes are effective and what are detrimental we know that if we if we have some particles introduced that are too large they could help encourage precipitation and have the opposite effect and it may be the case also that if they're |
| 38:43 | too small under certain circumstances they may also have the opposite effect and so once once we do know what size that we need um can we produce them in sufficient quantities we we need to to produce really immense quantities very very small so small amounts of mass but immense numbers of these cloud condensation nuclei to be able to have any meaningful impact and we'll talk a little bit more about that later um next what is the envelope of cooling and shading that can be achieved and is it enough to provide benefit |
| 39:20 | so the clouds over the reef are not the ideal clouds for marine cloud brightening they're not uh large persistent decks of marine stratocumulus clouds in general there is some stratocumulus clouds but but there's more trade cumulus which are less ideal for cloud brightening but in the case of trying to prevent corals bleaching we don't necessarily need the very very best clouds in the world what we need are clouds that are good enough to have an impact that is enough to help preserve the great barrier reef |
| 39:51 | and then given that what are some realistic engineering design assumptions around nozzle performance and and the energy requirements so even if we can create enough cloud condensation nuclei uh in in a sort of a single station if you'd like um how much energy does that require and is it reasonable to scale that up to be large enough to to do an area as as big as the great barrier reef which is some 350 000 or so kilometers squared very large area even though it's a very small fraction of the earth and so we'll move on now to looking at |
| 40:28 | addressing some of those technical questions and then the next part of the talk is is just looking at some of the things we've done in sort of preliminary work to start to address these questions and this is some preliminary fairly high resolution cloud micro physical modeling to get a first impression of whether the clouds over the reef are in fact sensitive to additional ccn during the period that we're interested in and the results from this uh suggested that that an albedo increase of up to around 0.3 |
| 41:00 | um from just considering the toomey effect alone not including also the the potential direct effect of the aerosols themselves and also not including any potential uh second indirect effects of cloud brightening uh such as increased cloud lifetime due to decreased precipitation and other uh second order impacts um and so that that was quite encouraging um but it is quite preliminary modeling and that's published for those that want to have a closer look um and so next we we move to the hydrodynamic modeling okay so if we can |
| 41:34 | if we can get an albedo increase in the in the clouds does that translate to an actual cooling of the ocean or is there simply too much water moving too quickly to cool and so for this we're quite uh lucky because the csiro in australia has spent many years uh with partners developing a very very accurate uh hydrodynamic model of the great barrier reef which which also has within a bio geochemical model and and even a coral bleaching model which i'll show some results of later but the point here is that it gets the |
| 42:03 | hydrodynamics very very right um the root mean square error on the water temperature is is less than a degree i believe um i think 0.3 from memory and so on the right there it's it's just a few of the scenarios we run but actually sorry on the left actually shows um a scenario of 0.3 albedo change to just the low cloud fraction uh during the 2015-26 year so the actual conditions that that bleaching occurs under and and like like allen found um it's interesting that and this was a bit of a surprise to us that that the |
| 42:42 | cooling is so isolated to under the cloud that that's impacted we expected that the the water movement would would sort of advect that cooling influence a lot further but but the direct cooling is is really shown to be quite so so that result there is is actually also quite representative of the the spatial um distribution of the forcing although what we do see of course and you can see it in the right panel there as well whether the results are plotted for each individual reef within the gbr ecosystem that um that as you as you |
| 43:19 | move uh from the edge of the shelf in towards the coast the amount of cooling that's achieved increases and and that of course is because the residence time of the water under the changed cloud increases as you as you move away from the edge of the area that you're influencing and so we can summarize those results in in this plot from a whole bunch of different scenarios and and i guess that the without talking about this too much the the main takeaway point here is that that using i think perhaps optimistic |
| 43:51 | but reasonable assumptions we can probably achieve something like 0.6 or 0.7 over of a degree change in temperature um of the surface ocean across the gbr well not all of across this this is sort of an average meat shelf and what we also discovered by changing the scale of of the area that we were conducting cloud brightening if you if you go out to that whole model domain so well out into the pacific ocean um you can get a an extra 20 or so of cooling and um if you sorry an extra 40 and if you reduce the um the area down to only about a quarter or |
| 44:31 | so of the gbr you you lose some efficiency about 20 but you you still get about 0.5 degree cooling under that particular scenario if we then move to the biogeochemical component of that modal model to look at the coral bleaching what we find is quite interesting because we're reducing both the light and the temperature um we're able to reduce a lot of the stress in the corals and and because the biogeochemical model can only be run in a nested configuration at a very high resolution we we had to do this for a representative |
| 45:06 | sample of reefs not all of them many more than a shine on this slide though and what we found was that um with the lower cloud cover during 2015 2016 we were able to reduce the bleaching stress by about 50 um and that was because that was such a strong el nino year in 2016 2017 that was about 65 um we haven't yet been able to take the step to translate that to mortality but we suspect it's very high because um the the mortality is um is sort of results from peak stress so by reducing the stress by 65 we we think that you reduce nearly all |
| 45:47 | of the mortality and if you then take those results and you put them in ecological models that are being used to predict the future of the reef i'll just spend a little bit of time on these slides but um if you look at the the two panels in the middle there the dashed line there is the same in in both and that's the future predict prediction of the reef without intervention and and of course it's also it's not the same because the top one is um a parasite climate scenario and the the bottom is a more business as usual |
| 46:20 | type scenario and um but you see in both that that the reef goes through a period of decline and if we meet paris it levels off with some coral cover remaining the y-axis there is is fraction coral cover on the reef um although in a in a business as usual representative concentration pathway of 8. |
| 46:43 | 5 what's forcing we lose the reef completely and then the the solid line of course is is with the cloud brightening intervention and this is a really really important result i think because if we have a paris type commitment to climate change and and emissions reductions and we also do cloud brightening uh this model result shows that that it's possible to to have the reef balance back to its previous levels at recent levels of health and to to sustain that at least out to 2075 which was the model run um however if we don't have really |
| 47:15 | really strong action on emissions um then then the cloud brightening uh essentially delays um the degradation of the reef by a couple of decades but but eventually there's only so much uh scope for brightening the clouds you can't just keep adding more particles and getting more cloud brightening so you eventually run out of scope and simply you're overcome by global warming another interesting finding of this modeling was when we combined interventions so not just cloud brightening but but some of the other |
| 47:45 | interventions that the reef restoration adaptation program is looking into that they nearly all synergized very very well with cloud brightening so helping to relieve some of that stress helps you with other restoration and and preservation interventions that you might make on the reef um the last part of the talk is just looking at some of our results from recent field studies so we've we've been out to the reef twice now um testing a cloud brightening prototype which is not so much a real prototype but |
| 48:18 | rather a test rig i'd like to call it and and the idea here has been so far not to influence the clouds um but to start to look at some of those engineering type questions which you can't answer in the lab so there's been uh probably a decade or more of work prior to this time working on nozzle development in the lab both both by others and also by ourselves at the university of sydney this workhorse but now at the university of southern california we've been fortunate enough to to get enough funding to |
| 48:47 | take this idea uh out into the field with the support of the traditional owners who who own these waters we we don't do any work in the field without the free pro and informed consent of the traditional owners that that have historical uh access rights over that that area of the great barrier reef um and and also obviously with the the permissions of the the regulators which in this case is the great barrier reef marine park authority so the research areas is very highly regulated and of course there's a |
| 49:16 | permitting process to go through first and you could try and wind up in about two minutes yep sure by by probably going fast and so this is just a bit of a schematic about how we've been doing some of the field work um but here are some results that will probably interest some um so now our most recent experiment we were producing around uh 3 times 10 to the 14 particles per second uh with the size distributions shown there on the left an important point here i think is that um if we if we take rob woods uh recent uh |
| 49:55 | prediction of of of a good of sort of effective uh size range for cloud brightening that's the yellow shading um and a sort of perhaps more restricted um uh representation of the more ideal size perhaps there the larger and more narrow sizes there in the green shading so currently the size distribution fits quite well um at least for 2020 we tried new nozzles this last year to try and push the size distribution larger but it actually just broadened the size distribution so it didn't live up to expectations |
| 50:32 | um and this result shows the the results from our drone flying back and forth during the plume and the takeaway message here was that um we were worried that the evaporative cooling of the evaporating sea water may cause the plume to sink and flow across the ocean at least in some atmospheric conditions um but we we've now tested across a wide range of atmospheric conditions and in fact there there seems to in the summer due to the very hot ocean um be generally quite an unstable atmosphere and very good vertical mixing |
| 51:02 | of the plume um but a final slide here i'll just put all of them up there but um essentially what we've found so far is that uh 10 to 20 watts per meter squared average reduction over the summer is enough to to alter the trajectory of the reef ecological modeling show just just 0.3 of a degree reduction in ocean surface temperature is enough to alter the trajectory of the reef um the evidence continues to suggest that the clouds over the reef do appear to be susceptible to cloud brightening um the plume is well |
| 51:36 | mixed vertically and and and so we we've uh results so far have suggested that our particles reach the cloud base in only around four to six kilometers downwind generally um size distribution is not yet ideal we think that we need more like the historical um assumptions around size uh for the clouds over the reef for technical reasons i don't have time to get into and and finally that that we're we're very close to being able to produce enough sea salt aerosols in a in an experimental sense to begin to |
| 52:08 | look at their influence on the cloud micro physical properties um and and of course the the really critical result there that uh the this research isn't going to be useful in terms of helping the reef and unless we also have strong reduction of emissions thank you thank you very much dan could i just give you a question that's come in from john nan is cloud brightening assuming a very evenly distributed effect does it rely upon stratiform cloud versus cumulative form cloud and if uneven he wonders whether the |
| 52:47 | seeding may change stratiform cloud into more cumuliform fields with potentially strong penetration between clouds the last points are an interesting one which is um which i haven't considered too closely and and would be one for the for the more um uh true cloud micro physicists rather than the oceanographers like myself what i can say about the the uniformity though is that interesting some of those scenarios i showed um that resulted in that nearly linear um relationship between average forcing and uh sea surface cooling um were were uniform |
| 53:25 | forcing fields so so sort of um in a sense representative of direct forcing sky brightening perhaps rather than cloud brightening and the result there was that between the movement of the clouds and and the mixing of the ocean it made made essentially no difference whether the forcing was was applied just to the low clouds um or was applied evenly over the same area the the ocean cooling was was essentially the same for a given amount of average forcing but the the second question i'd have to take on notice and consult with the |
| 53:59 | cloud microphysicists dan thanks very much i've got a bunch of questions coming in but we'll hold them for the for the general discussion um i i do have a comment which is that you're saying of course we need deep and rapid emissions reduction uh even if you continue with your work to try to manage the great barrier reef but of course we would say reduction isn't enough we need to remove greenhouse gases that are already in the atmosphere to get ourselves back to the position where for example the great barrier reef |
| 54:38 | doesn't need these continued interventions but let me just say thank you very much for a very clear presentation now the next presentation is from dr leslie field and dr leslie field is the founder and chief technical officer of the arctic ice project a lecturer at stanford university and the founder of small tech consulting llc her work includes arctic ice restoration teaching at stanford and consulting in the area of microelectromechanical systems and nanotechnology now leslie is not available to us at the |
| 55:21 | moment but we have a pre-recording of her speech so i'm going to pass this over to my colleagues to see that you now are exposed to the pre-recording thank you hello i'm dr leslie field and i am so honored to be a part of this impactful series of workshops i'm disappointed not to be able to be there live during the discussion section especially please send any questions to me at l field at arctic iceproject. |
| 56:03 | org and i'd love to have a conversation with you later why am i not able to be there original date i coulda but as it is with the change needed in the schedule i'm already locked into a backpacking permits in the rocky mountains with my son our youngest son gregory and those are not arrangements that can easily be changed so my apologies um think of me in the mountains um just delighted to be here and and i'm very happy to be speaking about localized albedo modification localized surface albedo modification |
| 56:38 | for ice preservation and regeneration thank you um you've probably seen uh movies like this um and i hope you've been discussing this to some extent already as well um but in case uh this is your first uh that you're looking at during this seminar series the idea about arctic ice why it's so important to climate change is that it has been disappearing rapidly in a positive feedback loop over the last just several decades so here month by month you can see as uh professor don perovich calls it the beating |
| 57:18 | heart the breath of arctic ice as it's melting and re-freezing over time what's happening though is that sea ice over four years old is brighter right you can see the brightness that they're reporting is brighter as ice ages and the inventory of sea ice over four years old is disappearing is reducing over these years and so it's not just temperature rise although that's a good deal of it warming ocean rising temperatures atmospherically as well it's ice export as well things have changed a lot |
| 57:55 | and so as we lose this bright reflective ice we're losing the planet's uh historic icy heat shield in the arctic that used to fend off much of the 24 hour per day sunlight in the arctic in the summer and that's a big deal that has added our heat load to the planet and is accelerating global temperature rise enormously and you can see this isn't just some short-term weather variation over the course of these decades it's gotten more and more rapid and it really looks like there is no natural way back |
| 58:30 | to have the ice reappear if we just do nothing if we pull down co2 if we pull down greenhouse gases if we can cool things a bit then yes uh ice could very likely come back we're lucky enough to keep reforming it every winter but it's young peanuts that doesn't reflect much increasingly and so this is a devastating impact on our planetary systems so the loss of older ice means loss of brightness loss of albedo and as professor peter waters has said in his beautiful book a farewell to ice this overall change in the arctic adding |
| 59:09 | land ice and sea ice together can add as much as 50 percent accelerate by 50 to the direct level heating effect that we've already got in the atmosphere of co2 uh dr don perkich another wonderful ice expert says that back in march of 1985 old ice comprised about 30 percent of arctic sea ice covered now a couple years ago he was addressing the american geophysical union delivering the noaa report card for that year a couple years ago now it's about one percent so we've really lost enormously of beautiful reflectivity |
| 59:46 | that we've historically had in the arctic um there are a lot of considerations if you want to do something about that though and i as a sort of terminal technologist you know the first reaction is let's make a technical solution and that's true we need technical solutions but we also need to consider the whole framework and i really love what our colleague dr danielle chamberlain at arctic guy's project has put together just showing some of the stakeholders and some of the considerations we really |
| 1:00:16 | need to include if we're going to start considering doing any climate interventional solutions i've been passionate about trying to make sure that we understand and if necessary help form the policy and governance discussions and decisions that will allow people to understand who can impartially evaluate what is actually in the best interests of humanity and we have to we have to consider everything especially the people who actually live in the regions that we're thinking about doing uh interventions in there's a picture of |
| 1:00:54 | us with with some of our up in barrow alaska where we've done a great deal of testing over the years so these framework considerations are key here it is in a little larger format for you and we have a proposed solution that's been working into that framework uh from the beginning i i from the beginning i have known that first do no harm was going to be my most important principle if we're going to make an intervention then for pete's sake let's make sure that it doesn't harm something that we |
| 1:01:28 | could undo it if we needed that it's not harmful in the first place um after many years of testing many materials in various locations our favorite choice is silica glass hollow glass microspheres and these are commercially available that's very key you want to make sure something you don't have to bring up a new manufacturing process in order to do this this is a close-up of the spheres this is what they look like in a little jar they're basically look like a foot friendly sand white floating sand and they are |
| 1:02:04 | used widely in many many applications right now there's a number of these properties that are very deliberate i didn't want anything to be able to bind with oil-based pollutants hydrophilic is really great once we distribute them they cling to the ice or water because they want to stay there they'll flow around with waves after a melt but they stay and it's one of silica the major component of these hollow shell forming a hollow shell around a gas sphere that reflects away sunlight um silica is one of the most |
| 1:02:35 | abundant materials on the planet so we've all evolved and it's very prevalent in marine and and land ecosystems and it's very different than plastic it's passed all the safety tests so far but we're continuing to test test tests we're raising money to collaborate with marine biologists who can help look at some of the more subtle aspects of this that are going to be very important and basically a thin coating takes us from that open ocean almost no reflectivity of incoming sunlight and beyond the thin ice uh you know |
| 1:03:09 | measurements that uh actually don perovich's group has done many many ice albedo measurements it'll pull us beyond that to instantly boost the reflectivity of young thin ice towards what one could have with very old ice especially with a snow cover and over time if we can preserve this over a melt season we then form the basilar on which the next season's ice can grow and we start to be able to reboot multi-year ice we're looking for that we're looking for the right locations where that could happen |
| 1:03:44 | we've done control tests for years in collaboration always with the local residents here's somebody from uic science up in lutkegvik corey with an instrumentation volunteer who's worked with us on and off for many many years satish and that so this is in a chaotic drilling and ice core of course and here's a pond in minnesota where we have a mighty team of volunteers in a backyard pond and here's the materials put out on you know square by square so we get even dosing on a treated section of the pond and |
| 1:04:18 | here's untreated control so that we can study what's going on um here's that same pond uh different year this year with bare ice and then treated with hollow glass microspheres and you can see it's an instant boost in reflectivity this really bright area of course is snow you can't beat snow but snow it's not a problem for these if snow falls on top so much the better once it melts we find that the hollow glass microspheres are very effective on melt water this year we had the best most solid |
| 1:04:51 | most data rich data set we've ever had on a test pond in minnesota it was real time reporting here in california from the pond in minnesota and this is just a sample of the kinds of things that we were measuring here's some drone footage we had from overhead right after application and then into the melt you can see we segmented the pond with a thin pipe actually and we've done uh ice melt comparison with a sequence of drone footage and these measurements the data reduction is still in progress so we're not quoting the numbers quite |
| 1:05:26 | yet but we will publish a scientific paper promptly when the analysis is complete but what we got to see was the starring thing was that as soon as all the snow had melted then the hgm's are really taking on their role to increase reflectivity over what the underlying ice was and so floating on top of the melt bonds so that's terrific and this lets us be bold enough to say that we could probably help with glacial ice as well and that's huge because we have crises in greenland and the himalayas uh at risk the drinking water for over a |
| 1:06:02 | billion people from himalayan ice melt and global sea level rise threatening all coastal communities if all of greenland went and so we'll continue to say that the hdms we have data we have quantification coming on how effective they are on melt ponds and so far everything looks safe but we are going to continue to test test test and make sure that this really is safe if not we're silicon valley we can pivot a material if we need to we have many people on our well most of our technical team is expert in |
| 1:06:38 | materials and we can make the pivot if we have to um we do climate modeling through a partnership with climb formatics a mighty team of experts here and we've been modeling with them they've been doing the modeling a couple of strategic areas in the arctic that might allow us for leveraged deployment that is something that will affect have beneficial effects beyond the small area that we intend to treat and that's a very key thing the indications all are that we don't need to carpet the arctic there's a lot more modeling needed in |
| 1:07:16 | order to get this all vetted out of course the cost of doing nothing is huge and the impacts are devastating this is a noaa national oceanic and atmospheric administration a map of the impacts in just one country the u.s in just one year 2018 where the costs were almost 100 billion dollars and of course the climate's getting less stable so the impacts are getting worse and worse to not do anything is really it's unconscionable it's just it's not in the best interest of humanity that's for sure |
| 1:07:50 | on the other hand we do want to make sure that interventions that are made proposed and then eventually funded and implemented are going to be ones that are actually in the service of the best interests of all of us and so restoring polar ice this tragic outcome the loss the melt is a tragic outcome of global temperature rise but restoring it is a crucial lever that could slow climate risks and harms while the world urgently decarbonizes i mean why not just do that it takes time it takes time to turn over the infrastructure these sorts of |
| 1:08:25 | interventions are a band-aid a temporary help to slow that global temperature rise and global climate devastation down while we get to do job one which is that urgent decarbonization and this is the time to act it is almost too late to be able to prevent these enormous harms we're building collaborations to accelerate the work i would welcome collaborating with you and again please write me if you have questions or want to follow up l field at arctic iceproject. |
| 1:08:57 | org thank you so much take care bye-bye of course we don't have leslie with us to answer the question but it's a good one it comes from hans van der lu and it's been so upvoted by quite a few other people can the hollow glass microspheres the silica enter the food chain in the way the plastic is doing or do its characteristics mean it would not be digested and leave any body unchanged i think that is a question that must be on leslie's menu of things to be done in terms of her experimentation and it's certainly a question that we |
| 1:09:56 | will pass on to her i'm now going to move straight on to our last speaker of the day our own dr hugh hunt who is deputy director of the center for climate repair here and a reader in the department of engineering at cambridge university he is also a fellow of trinity college here in cambridge he stepped in to talk today at less than 24 hours notice very keen that i should let you know that his most recent research is in the fields of renewable energy and geoengineering including the spice project he took his first degree in engineering from |
| 1:10:36 | melbourne university i think you'll tell from his accent in australia and has a phd from cambridge university he is going to give us a talk i think on marine cloud brightening and describe the experimental work underway at cambridge and edinburgh and of course working alongside alan gadien at leeds over to you hugh well thank you very much dave um yes um i've uh hopefully i can do my best to do some justice to this topic in the in this afternoon's presentation it's been really interesting to hear |
| 1:11:18 | the earlier speakers um i i grew up in australia and um really you take the great beer barrier reef for granted it's a it's a beautiful place and it's um and it's threatened uh and we've we're in a position now to be able to do something about it and about other threatened parts of our planet and now let me just share my screen here which i think i can do hopefully you can uh can see that so the um the the arctic uh in particular is is threatened um we've heard about arc amplification yes |
| 1:12:02 | the world is warming but the arctic is warming faster and we've got to come up with techniques to to try to uh to to manage this warming yes we've got to stop emitting co2 and methane and other greenhouse gases we've got to stop burning fossil fuels that's that's number one as we've we've we've heard several times today we've also got to try and get carbon dioxide and methane out of the atmosphere the stuff that we've already put in there but what we're talking about today is |
| 1:12:35 | ways of reflecting sunlight and now solar radiation management as it's uh as it's called i don't like that name management suggests that we're we're in control of things but solar radiation management uh comes in all sorts of different forms and you might have come across some of these forms with um the uh perhaps reflecting sunlight by making the oceans more foamy that that's been talked about perhaps increasing the reflectivity of the land perhaps we can use genetic modification of crops to make them more reflective |
| 1:13:15 | we've heard a bit just now of increasing reflectivity in in polar regions perhaps we can increase reflectivity of deserts but there's there are two that are particularly interesting there's increasing reflectivity from uh clouds and increasing reflectivity in the stratosphere and um so marine cloud brightening is this increasing um reflectivity from low clouds and stratospheric aerosol injection we heard about on monday is increasing reflectivity high in the um the in the atmosphere now a question that was asked on |
| 1:13:51 | monday is whether marine cloud brightening is it is it possible that marine club writing could could marine cloud brightening could be as effective as stratospheric aerosols so i just quickly want to to sum up in one slide the stratospheric aerosol idea which is that well we know back in 1991 that mount pinatubo put about 10 million tonnes of sulfur dioxide up above 20 kilometers and if we wanted to achieve say a two degree per year cooling question mark is that what we'd be interested in we'd need about |
| 1:14:28 | two pinot turbos let's say per year and based on what we know from uh mount pinatubo we've got a reasonable estimate that that means putting 55 000 tons per day of sulfur dioxide up into the stratosphere now to do that we'd need with 10 tonne payload aircraft can we do it 5 500 flights per day which sounds completely nuts and it is completely nuts but i just want you to bear that figure in mind because it'll come back again 55 000 tons a day of sulfur dioxide which by the way compare that with the 100 million |
| 1:15:10 | tons per day that we on this planet generate in our co2 i mean i think it's crazy that that we we we start being nervous about figures like 55 000 tons a day but this figure we kind of just brush off anyway that's another point for another day so what if we were to do marine cloud brightening and i've tried to kind of pick up on comments that have been made before if we're going to spray sea water into clouds to re increase reflectivity well let's try and do some sums and i'm grateful very much to stephen |
| 1:15:44 | salter who's um who's done quite a few of these sums um to keep us on our toes we're trying to increase reflectivity and he's been suggesting that well if we could increase the number of cloud nuclei um the uh um to maybe about 50 then that'll increase the the amount of clout he suggested that to do this we'd need uh maybe a hundred spraying ships each generating 10 to the seven it's 10 to the 17 salt water droplets per second well daniel was talking about these amazing numbers big numbers |
| 1:16:28 | if we just get trying to get a handle on this 10 to the 17 saltwater droplets per second these salt water droplets need to be 0.8 micron 800 nanometers in diameter to produce 200 nanometer salt particles these cloud concentration nuclei we've heard about them earlier now that translates to 230 000 tons of water per day so compare that figure with the 50 000 tonnes of sulfur dioxide you kind of think i'd much rather be spraying seawater even if we have to spray more of it than than sulfur dioxide it just it feels right so what's really |
| 1:17:15 | imperative is that if this technology can work on this sort of scale then we've really got to work out can we do it and this then becomes an engineering problem and yes of course there's all sorts of climate modelling stuff required there's no doubt about that now the climate modeling there is some some variability if you look at these various pictures which come from i mentioned at the bottom here cabela stern's marine cloud brightening research at the cicero lab this is from a couple of years ago |
| 1:17:52 | there is a lot of difficulty in being sure about how clouds work clouds are really tricky to model now what we're doing in our center for climate repair is to do uh modeling of the of the climate and of clouds to try to be sure that the anticipated effectiveness of marine cloud brightening can be realized without unacceptable adverse consequences we've really got to be sure and the modeling of the climate is pretty important but that's kind of i'm not going to say that's the easy bit but that's that's the bit which has been |
| 1:18:32 | given quite a lot of attention uh over the years up until now the the bit that gets more difficult is this um the sort of cloud physics bit where we've got salt particles which already they're they're they're lashed up by winds out in the sea and the waves and the spray produces tiny droplets those droplets evaporate the water evaporates leaving salt particles and they make their way up these cloud concentration nuclei wake that make the way up and they help to to create the clouds that we see but it's |
| 1:19:11 | all very turbulent it's all very it's all very complex so that is an area of modeling which center for climate repair is is involved with as well and how we how we do that modeling is pretty important we've got to make sure that we don't just generate droplets and particles that in the end don't end up making new clouds but the thing that's really exercising our minds at the moment is how we generate the spray now one thing that i think is quite almost amusing is that the fossil fuel world is generating droplets um tiny |
| 1:19:51 | droplets of um of diesel fuel and of other fuel to go into engines to uh create the the the power that we we demand they know a lot about droplets and so that's the other thing that we've got um in here in cambridge is we do have a large research base on optimizing the performance of engines and i think it's it's really significant that we can take up uh this battle from the uh from the people working in uh droplets for diesel engines and start looking at using the same technologies for droplets |
| 1:20:33 | to produce whiter clouds now the graph on the left shows you a typical example of the kind of droplet diameters that are being talked about for diesel engines and they're measured in tens of microns so we've got to bear in mind that we've got to be thinking perhaps of different technologies different ideas for generating droplets and that's really interesting something interests me very interests me very much but the way that these droplets are produced goes back to um lord raleigh back in 1878 when he was looking at how |
| 1:21:12 | droplets break up um you have a stream of water or whatever liquid it might be and there's an instability which produces droplets one of the key things which we're interested in is that if we're going to produce 800 nanometer droplet sizes we've got to try and make sure that that droplet distribution size distribution is uniform we don't want to find that yes we're aiming for 800 nanometers but we get anything from 200 up to 5000 because that's not good enough because what then happens is those |
| 1:21:45 | droplets uh the the water evaporates to give us those those really ideal 200 nanometer salt particles so then we start looking at the the um the droplet generators that we can just get off the shelf it'd be great if we could use uh the kind what we all know if you if you're spraying a garden with a with with something or if you're you've got a spray paint you want to to top up the to to touch up the paint on your car no there's all sorts of nozzles out there but if you start again to look at |
| 1:22:18 | the droplet size from these nozzles you're really pushing it to get droplet sizes down below four microns so then we start thinking well what about the uh the the the inkjet um industry you know inkjet printing we've we've got prop there's one sitting on my desk here as i speak and it's absolutely amazing what has been done um to make inkjet's these droplets of ink just function perfectly well um you know there's got one of these things on their desk but again if you look at the diameters |
| 1:22:57 | these droplet diameters are tens of microns again but the one thing we've got to remember is the way that these are jet generated it's done using micro electronics silicon substrate with um vibrating um components to and and warming the liquid up and so on to produce droplets of just the right size so what we are currently engaging in right now is to take um designs that stephen salter has um has prepared already in edinburgh and to to build them and to optimize them to see if we can get these 800 nanometer droplet distribution |
| 1:23:43 | um that we need now um the just to sum up then the things that we're looking at climate modelling where when how much um uh cloud brightening do we need it's all very well to to know all that but as has been mentioned before you can't just wander in and uh and and start brightening clouds without really full and proper engagement with local communities and full on proper public involvement one of the things i learned from the spice project that's our stratospheric particle injection for climate engineering is that even if you |
| 1:24:22 | want to do a relatively what you might might think of as a benign experiment you discover that there's no such thing as a benign experiment when it comes to this kind of stuff we're talking about we had a really good session right at the beginning of this summer series on the ethics and governance of marine cloud ethics and governance of carbon dioxide removal and you might think that carbon dioxide removal is kind of a no-brainer you know why let us do it but it's not entirely clear that it has um that it's without uh ethical and |
| 1:25:01 | governmental uh impact so the technical things droplet generation what is the right size um there seems to be consensus more or less that we're aiming for 200 nanometer cloud condensation nuclei but the research is not conclusive there there are people who are saying oh we should go smaller and others we could say it's easier to go bigger we've really got to be sure that we're going down the right direction and then how do we make those droplets and of uniform size and these eye watering numbers 10 to the |
| 1:25:39 | 17 droplets per second can we do it scaling it up is the hard bit now producing these uh 200 nanometer cloud condensation nuclei lofting them into clouds looking at the residence times looking at the cloud physics now all of this is um is fabulous but we're not uh we're not one tracked on this because there are other um ideas that perhaps instead of producing these nano-sized salt particles by evaporating water from from sea water can we do direct dusting of dry particles and there's a lot of thought that this |
| 1:26:21 | is a natural process in itself with um with with dust blowing off the land over to the over the uh over the sea uh producing condensation nuclei that way too so apologies that this hasn't been a particularly enlightening presentation but i'm very pleased to have been involved today and thank you very much for listening and thank you very much hugh and i do have a clarifying question for you from somebody you know well and i know well jamie arnell he's asking does the salt precipitate out and contaminate |
| 1:27:04 | ice or land with salt so yes of course the salt eventually comes down as rain and but we're looking at a 50 increase of cloud condensation nuclei in those areas um where clouds are most likely to fall so this is um uh and and in any case this the intention is this is done over c so hence marine cloud brightening so yes the the these the salty the salty the salt will come back down again into the sea where it originally came from um there would certainly be questions to be asked if if this salty uh air were to be |
| 1:27:56 | blown over land and of course we need to be very careful about that um but i think the short answer is it comes back into the sea which is not especially problematic well thank you very much hugh i i'm now going to call on the uh three loca members who who are available to us for the general discussion and uh and ask some more questions that are firing in and they are being selected out for me so i'm just going to read a few um i've got first of all uh maybe this is a start for for alan but anyone is welcome to answer |
| 1:28:43 | can you explain to everyday people apparently we are all everyday people aren't we uh what's happening to the arctic would be would it be true to say that the arctic and the antarctic actors refrigerators to the world and that carbon emissions are defrosting them hello it's alan allen here first of all if you look at the i know we're diverting a little bit if you look at the planet uh on other planets in our system mars you find that the polar ice caps actually melt and transfer to the other side of the |
| 1:29:21 | globe so yes these these um these polar masses are actually huge effectively refrigerated storage refrigerators and they they store a lot of liquid water um and therefore they you can regard them as as ways of keeping the planet cool and uh the interesting fact the scientific factor is that the planet absorbs solar radiation admits it to space and in the equator regions it absorbs a lot of incoming solar radiation and the polar regions it emits it just back out to space so it is in fact yes a giant refrigerator but if i may can i just comment on the |
| 1:30:11 | question about salt that that's hugh was asked in fact the amount of sea salt we're putting up into the marine carb brightening is less than one good atlantic storm a good atlantic storm in the mid winter will throw up all week and far more than we can do in a year so yes hope that answers both questions thank you very much and i've i've got uh another question from faye which is for these techniques to give a short-term solution to climate change who is responsible actually this question could be for me as well |
| 1:30:52 | for financing the technology and for its implementation who is responsible uh let's rephrase that perhaps as who is going to well can i just can i perhaps just uh say first that research needs to be done and research is relatively cheap and it's disappointing that research seems to be quite difficult to do and quite difficult to get funded because i think of the questions about who ultimately will be paying for implementation if ever we do it and who ultimately have their hands on the thermostat and who |
| 1:31:43 | ultimately will be in control it's a shame that we can't get on with the research while at the same time coming up with an answer to the question that's just being asked i'm going to suggest that the the answer would be all of those who are affected by these impacts and uh surely if we are looking for example at sea level rise as ice on greenland melts as ice in the antarctic melts etc then we all benefit and we are represented by our governments i would have hoped that our governments would step in and fund |
| 1:32:21 | the the bigger effort required um there are of course philanthropic bodies that can take us quite a long way as well but uh i think that was uh that was a pretty important question so daniel is the australian government interested in um in in helping to pay for the restoration of the barrier yeah i'm happy to talk about our funding so um our funding for our work has been a mix of philanthropy and government funding some of the government funding um competitive so the the first first um experimentation we were able to do out |
| 1:33:00 | on the reef was uh through a jointly funded um competitive call for interventions to help coral abundance on the reef which was funded jointly by the queensland and federal governments and and the reef restoration and adaptation program uh is funded um through uh by the great barrier reef foundation um largely using funds from a large government grant that was was made to that foundation as well as attracting additional philanthropy so so a mixture of of government and philantrophic uh funding can i comment as well |
| 1:33:36 | i received some funding to do the work from via securities rooms from bill gates and he he funded it but in my quotations i usually say if you gave me harry kane's salary for five years or rooney as it was then i could we could fund all the research in the country and if you gave me one percent or 0.1 of all the funding for covid we could we could we could set up a system good um let me just go to what i think is another good question how can mcb marine cloud writing interventions planning take into account inter-annual |
| 1:34:21 | variability unprecedented changes in wind direction or perhaps in a heat dome effect in australia but also more particularly in the in the arctic so this is directed again at all three of you can can i start with that then a very quick comment if you look at marine stratocumulus clouds under the three areas we mentioned there is actually very little change in the in the dynamics and the structure of the meteorology in those regions it's in it's in in when you've got the meandering jet stream in the northern hemisphere in the |
| 1:35:00 | southern hemisphere you don't that's the big difference between northern hemisphere and southern hemisphere there are big local differences but if if if you just chose those and i'm not saying you should just change or the regions of australia there isn't actually that much difference in the local meteorological conditions as the planet warms up and uh i think it's quite similar for the for the reef um during during the the bleaching season the meteorology of the reef is is dominated by by trade winds coming from the |
| 1:35:34 | southeast but you do have periods uh where the winds switch westerly they're normally quite brief and so during those periods um that are fairly brief the the wind actually then brings uh aerosols natural aerosols rather than cloud brightening sea salt uh from the land and so the cloud brightening would become less effective in those times so it's really a from an engineering point of view it's an optimization problem if you if you wanted to be the the very uh most cost effective implementation that you |
| 1:36:06 | could yes you'd need to somehow understand what the meteorology was going to do in advance which of course weather forecasting gives us the ability to do with some degree of accuracy um but beyond that it's really uh your effectiveness might go down um you know if the wind's blowing in the wrong direction from where you've sided your stations uh then you might be cooling water further out into the pacific rather than directly over the reef uh but that would still have some benefit um as some of the modeling |
| 1:36:35 | showed if you're actually cooling the water before it gets to the reef it helps you to protect more of the reef than if you only start as soon as the water hits the reef okay i think we've covered that one and the next one is what this is from sonia galami what negative environmental effects might marine cloud brightening in the arctic have what are we watching out for with these initial experiments as we perform them one of the things that that we know from climate modelling global climate modeling is that |
| 1:37:15 | there's there are knock-on impacts elsewhere on the planet so if we change the uh the temperatures let's say in one region on the planet we can affect that expect that to be impacts elsewhere and the impacts will not just be on temperature but they'll also be on on rainfall and it's very important that we don't accidentally create a drought or a flood somewhere else but of course we've got to be mindful of the fact that if we don't do anything at all we're going to have some pretty severe um |
| 1:37:57 | weather and climate impacts over the next few decades so we've got a we've got a balancing act to do yes if we do submarine cloud brightening and there are some adverse effects how much adverse effect are we willing to accept given that what we're doing is reducing the overall negative impact of climate change can i comment on that as well if you look at the clausius clapton equation you'll find that precipitation will increase over the globe as you warm it up so that's one thing but in my talk there was a hidden slide |
| 1:38:35 | which showed the effect on the models of precipitation globally and you we you can actually see that the effect of doing nothing means huge bigger variations in precipitation over different parts of the world than if you do perhaps double co2 and marine cloud brightening so the change although i don't have reluctance to believe numerical models at climate scale uh even though i spend my life looking at them there is evidence to suggest that the actually it actually reduces it but one of the frightening things was |
| 1:39:12 | that all the climate models i've looked at the there is a reduction as you increase co2 there is a reduction in rainfall in places like arizona and western usa and with the increasing number of fires there i i don't want to believe the numerical models climate models but all the numerical models climate models i've seen there's been a reduction in precipitation in the regions that are now suffering forest fires so there's going to be knock-on effects and that's why we want to do the coded |
| 1:39:48 | manipulation but the evidence suggests the knock-on effects are less than doing nothing thank you very much um there's a group of questions and they've been partially answered about the the particle size so in in marine cloud brightening work i think uh hue in particular has focused around a narrow particle size distribution for the sodium chloride crystals peaking at about 800 nanometers and so the question is to both the arctic work and the work done in australia what what is the reason for selecting a |
| 1:40:31 | particular particle size also alan had a slide i think which showed that um what why the 200 nanometer salt particle was was optimal um and but i think it's a really good question because the 200 nanometer salt particle size may be optimal but if it can't be achieved for some reason at sufficient scale then maybe we have to be looking around at other sizes but i think probably daniel and alan would agree that it's it's quite a good it's a quite a good size to be aiming for right now um but uh it's um a good question about |
| 1:41:15 | whether it's it's it's the holy grail or maybe there there are some other optimum optima out there that we don't quite know about yet i can comment a little bit in the australian context i'm sure alan will have plenty to say too um one thing that makes that size particularly attractive in the well there's two things actually that make that size particularly attractive in the australian context one is that uh with the the typical relative humidities that are exist over the reef during summer that |
| 1:41:45 | the hydroscopic growth um means that a 200 nanometer sized salt crystal um will typically result in a sort of um droplet at equilibrium size of around 400 nanometers diameter and so that's about half of of the size that you'd spray it out at and it so happens that that size is optimal for me scattering so for optimizing the direct scattering effect of those aerosols floating around in the atmosphere the ones that aren't actually contributing to to cloud condensation nuclear or perhaps are floating around when when |
| 1:42:20 | clouds are not present when the conditions for clouds are not are not right are not ideal then they're also making their optimum contribution if they're that size um i think the the size of 200 nanometers is it's a um it is it's been been selected because it's it's a um it's it's right in that gap and so it's a particularly um conducive size to forming a cloud droplet under a wider range of cloud conditions um so if you start to move away from that optimum it's not that you can't |
| 1:42:53 | necessarily form a cloud droplet but as particularly as you move smaller a decreasing fraction of those aerosols will activate to form cloud condensation nuclei and i think this is this is primarily where the discrepancy comes in between some of the work some of this recent work out of the states is is looking at particular cloud types and and i think the argument that there's a few that the the energy may also go up the larger the droplet size you produce so that's part of it but the other part of it is that |
| 1:43:25 | um as as as you decrease the size of the droplets it becomes harder from them to activate and a smaller proportion activate but if that means that you can more easily produce more of them if the amount that you can produce goes up quicker then their activation goes down then the optimum it becomes an optimization problem right and the optimum may not be at the ideal size for producing cloud droplets i would agree with daniel um the growth rate of droplets is ind is inversely proportional to the radius so the smaller they are |
| 1:44:03 | the faster they grow so that's the first thing the second thing that always worries me is engineers talk about diameter and i've just talked about radius and then you have wet size which is twice as big as dry size so i always worry about what actually we're talking about in terms of that the optimal size i think from a microphysicist is actually depends on the environment you're in so when i said geographic i don't mean geographic i mean the the water vapor the mixing ratio content of the local region you are |
| 1:44:38 | feingold who was an american very experienced cloud physicist he chose somewhere between 200 and 800 nanometers and you've got to work out the size so yes temperature and water vapor are critical and the background number of air assault as i showed on that plot if there's a very low aerosol content and so as long as it's not too big like a micron almost anything will do to to do it but there's not many of those cases where you get uh stratocumulus clouds with low very very low aerosol count so it's a complex i still think we're in |
| 1:45:16 | the right ballpark i think it will work if we stick in this ballpark but i think we could optimize it more to make it more efficient yes thank you very much i'm good i think it's it's possibly worth just noting just just because we're here and now that the particle size we're talking about is almost exactly the same as the coronavirus site so that's just puts it into context let's leave it at that shall we so so let me move on the question is really stimulated by nissar chatter but we we know there's a very recent |
| 1:45:59 | united nations environmental program report on the dramatic impact on human beings as the himalayan ice is lost and rivers dry up which are major feed channels for very large populations in that area is there any srm technique or srm like technique that could be used in re-freezing glaciers like the himalayas this is there's a lot i think it's it's worth saying that um the himalayan glacier issue is would have virtually zero impact on sea level rise but a huge impact to the people who live in those regions |
| 1:46:50 | so there when it comes to looking at srm solar radiation management to deal with global climate we've got to think about what the techniques what impacts these techniques will have on different different people affected by climate change so what will be the effects of on agriculture in let's say in california and what will be the effect of flooding in bangladesh and what will be the effect of sea level rise of the maldives but then the question of what will what are the ongoing impacts on on water supply in um on the indian subcontinent |
| 1:47:36 | i mean that's it is a huge concern and i don't think marine cloud brightening would have too big an impact directly on the himalayan glaciers um can i comment on that hugh i think you've hit the nail on i went to india to do some research project and about 80 percent of the water supply for india doesn't comes from not from the glaciers but from the monsoon however if you look to the north of the glaciers like uh china for example then uh it the the control of the glaciers becomes far more important because |
| 1:48:18 | water goes to china so there's geopolitical things there the the other point about um the marine cloud brightening if you would apply marine cloud brightening anywhere in the subtropics you are reducing the flow of heat from the equator to the pole that is that is the physics of what's going on you're not you might affect sorry daniel who might affect the uh your regions but the result is you're cooling down the equator and so in this transport so as soon as you do that the the atmosphere is a global system |
| 1:48:54 | you will affect directly well not directly in that sense because the atmospheric system will stop pumping all this heat towards the pole and you'll find the effects all over the planet not just what daniels is doing is not just affecting uh his coral reef but it's actually saving us as well but the time scales are significant in that um as so marine cloud ripening calls the um has a cooling effect which has a cooling effect on the arctic which has a there's a cooling effect on the planet my worry is that we lose the the |
| 1:49:40 | himalayan glaciers before those calling effects really have have kicked in i would agree with that you okay so let's move on it's becoming a little bit too challenging right now so we'll come back to all these problems um from rafe pomeranz how quickly could an mcb program and you'll see this is directed at you dan uh be initiated over the uh gbr if you were to look at the whole gbr and you wanted to run a full-scale project how how long would it take you regardless of finance requirements there's no easy answer to that question |
| 1:50:28 | because part of the answer is is how desperate do you become to do it i think um if you if you sort of extend current progress out it's that there's a very long way to go um the the droplet size that we're producing with the nozzles we have we is as we just talked about we don't think ideal and and it's a little bit of anyone's guess until um you know we we think that we're likely to get a positive effect um with a little bit of improvement of the nozzles but is that going to be enough will it give |
| 1:51:02 | us the result of the in the cloud microphysics that that we want we're fairly confident of getting that that result if we have the perfect droplet size we're a lot less confident um if we try with without the perfect droplet size and and how it would be anyone's guess but in terms of let's say that we were proceeding with the technology that we have now i think you're still looking at something like 10 years of of r d to understand the process sufficiently well um and to refine the the sort of the |
| 1:51:32 | science to practice well enough to be trying to do even even the the smallest meaningful portion of the reef which which might be a quarter of it or so um hugh gave a great talk on on how difficult it is to scale up um i think it's worth pointing out that you know that it's very easy to consider cloud brightening on these on these large scales using using models or using theory but the challenges of actually getting the engineering from where it is now to there is immense i'm not 100 confident that we can even |
| 1:52:04 | scale it up large enough to be effective for the reef let alone areas much much larger than the reef when when you actually look into the numbers and you and you look at the the amount of energy and the amount of droplets we can produce now and the efficiencies of how many you lose before they get to cloud height and you start to to add all of those things up um there's there's quite significant improvement but but that's not to say by any stretch it's impossible there's been very little effort |
| 1:52:30 | applied to this problem uh in reality until recently and there still is very little effort globally thank you very much very good reply so i've got a question in again from jamie arnell it seems counterintuitive that on the one hand the salt quantities needed are similar to one big winter storm and yet on the other hand this approach would have a material effect on ice in the arctic region is it likely that natural increases in storm activity with warming will do what we're envisaging without our intervention |
| 1:53:09 | the answer is no because because the the the aerosol is in the wrong place you've got to transfer that aerosol those particles we did the experiment of flying in the vocals and you were flying on flying underneath the clouds and the results came over the tower naught and i said that's impossible there is no way you can have zero uh and we found over hundreds of miles well periodically that there was no aerosol there the air was pristinely clean and that is like that every every day every day of the year in those regions |
| 1:53:49 | yet you go to the northern atlantic onto a stove then the aerosol level you just can't see because there's so much aerosol so i'm afraid uh these regions are uh it's like a high pressure you've got high pressure uh causing a heat wave and there is complete difference from maybe 500 000 kilometers off to the west where there is a storm going through or a frontal system the atmosphere is very uh segmented in many ways so yes i'm afraid that so it's under strata cumulus clouds that is the place to put the aerosol and |
| 1:54:27 | that is where it has most effect and other than in injecting it there there's no other way of getting the aerosol there i've got dozens of questions flying in but looking at the time i i fear that i'm not going to be able to put any of them to you so let me simply say first of all a very big thank you to uh the four speakers uh let's not forget that leslie's contribution was also very interesting um and and really the very very stimulating what what we are talking about in refreezing the the arctic is the need to buy |
| 1:55:16 | time i think we've just got to remember that the overall project is only going to be managed if we reduce emissions deeply and rapidly and if we bring greenhouse gas levels down to a level where these things are no longer threatening us and our belief in the center for climate repair at cambridge is that we have to do greenhouse gas removals at scale to bring levels down from the current over 500 parts per million please counting in methane properly to something like 350 parts per million co2 equivalent we're not going to manage that before |
| 1:55:59 | the end of the century that's why we have to buy time now so deep and rapid emissions reduction and even working as fast as we can on greenhouse gas removal we need to buy time while those are managed and this is why we have to talk about refreezing the arctic about saving the great barrier reef and about a series of other projects that that really are already showing that we're passing the tipping point now so i i just want to say that the objects of the climate repair center here at cambridge have been delivered through the series of |
| 1:56:42 | workshops and there are a number of people to thank in in developing these workshops uh first of all hugh wood himself hugh hunt himself where did i find that word wood from hugh our deputy director has been heavily involved in leading the development of these projects he's had a lot of help from rafe pomeranz so a big thank you to rafe and from dan bedansky the big international lawyer in climate change who's uh just coming to the end of yet another stay here in cambridge with us um the i i think i would also like to |
| 1:57:22 | thank steven salter who has contributed heavily to all of our thinking on marine cloud brightening and we are working closely with stephen and his team at the university of edinburgh but also now let me emphasize the importance of methane the rise in methane that has happened more recently than the rise in carbon dioxide is now heavily with us and it has reached the point that if we count methane against carbon dioxide at what i would call a proper level 140 times the impact per molecule in terms of its dynamic effect of the |
| 1:58:05 | temperature rise it would cause today it means that methane is as important today as carbon dioxide in terms of its increase on global warming it increased impact on global warming so we are now planning a next event in september which will be focused on methane removal so here in cambridge we are keen to work with universities around the world with governments around the world with public and private sector companies around the world because we we need to do this globally at a global scale to manage which is what is the biggest |
| 1:58:47 | challenge our civilization has ever had to face up to so thank you to all of the contributors to this series and i look forward to working with all of you as we move forward in time just before i leave you we have our artist tom mclean who's been busy doing sketches and whatever and i'll ask tom to put his sketch which is a a brief abstract of what you guys have been saying during this afternoon so here is his sketch uh tom thank you very much and yes he's enlarging it so we can read it in a bit more detail |
| 1:59:30 | it's a wonderful pictorial summary of uh of what we've been hearing about today just to remind us all so can i thank also the the staff who've been here abundantly helping us katie price antoinette who's both of them sitting here with me in our office in downing college uh we have relied heavily on the staff for all of the back up they've provided thank you very much |