cc  >> I would like to welcome you  to today's Chaos and Complex  Systems Seminar.  This is a seminar that's been  going on for 15 years now.  And we've had a lot of talks  recently about global warming,  and today we're going to have  another such talk.  One of the major issues with  global warming has to do with  aerosols in the atmosphere.  In fact, that's one of the major  unsolved problems and we have an  expert on that today.  Pao Wang, from the Department of  Atmospheric and Oceanic Sciences  is going to tell us  about the effects of  aerosol on global warming.  Pao.  >> Thank you, Clint.  I remember when my kids were  young I used to take them into  Clint's talk on the Wonder of  Physics and in one of them he's  just walking in a chaotic way  and saying that's a very nice  demonstration of chaos.  Today I'm going to talk about  the clouds and aerosol and their  role and impact in the  atmospheric and global climate  processes. 

 And I'm glad to be here to give  this talk.  Okay, so a little outline here.  Why do we worry about the clouds  and aerosols is the first part  I'd like to talk about.  And second is climate and  climate change, in general.  What are the processes that are  important to the study and also  how people are studying them.  And third part is how do clouds  form.  This is intimately related to  the aerosol particles.  And the fourth part is  the aerosols, their sources,  and sinks.  And then finally what's next  about this topic.  Okay, so why worry about the  clouds and aerosol?  Well, first of all, they both  play an important role in the  chemistry of the atmosphere  because both aerosols--  aerosols are, of course,  some kind of chemicals and  they react to these gases  and other particles, as well. 

 So they are playing a big role  in chemistry and the clouds also  in this sense play a very  important role.  Because clouds are important  surfaces exists also in a large  quantity in the atmosphere and  they serve as the basis for a  lot of important chemical  reactions to occur in the  atmosphere.  But these days are seeing the  most important things, of  course, is that they have strong  impact on the climate.  Many through this radiative  process.  And, of course, the magic word  here is global warming.  I think everybody knows that.  Because if you don't know that  magic word then you're losing a  big chance of winning a Nobel  Peace Prize.  So here we have these clouds and  aerosols and they all play  important roles here.  This slide shows the climate  change processes.  I took this slide from IPCC  assessment report number 4 last  year. 

 And this gives a very nice  summary of what's going on in  this climate change process.  Here you see that there you have  a natural influence which means  that you have things like a  solar processes, earth's orbit  changes and volcanoes shoot out  a lot of particles affecting  radiation, radiative objects.  And then you also have human  activities such as fossil fuel  burning, produce greenhouse  gases, also aerosol particles,  industrial processes, land uses,  changing the -- of the  earth's surface.  All these processes are feeding  into this direct and indirect  change of the climate  change drivers.  So here lists some of the  important factors to consider,  and you can see that among them  two are important in this talk  today is the aerosols and cloud  microphysics.  And the other, of course, is the  greenhouse gas and the solar  radiance.  And so after that they go into  all those changes.  These are four things and that  causes a lot of climate -- and  of course some feedback  processes including these --  chemical feedback processes and  I believe they have impact on  the human society and the human  society, again, will have impact  back on this whole process.  So this is sort of a simple  trial to show that what is this  climate change process.  Okay, and I believe you have  seen the chart probably many  times. 

 This is the radiative balance of  the atmosphere earth system.  It has many numbers there.  But to put it simply is that  there are three numbers that are  circled in red.  This is 342 watts per square  meter is the incoming circular  radiation.  So that comes in.  And then here you have another  107.  That is the one that gets  reflected by various processes  either by surface or by clouds,  aerosols and so on.  So, first of all, you already  have the effect of clouds and  aerosol right there.  Here is the estimate 77 watts  per square meter.  If you change the amount of the  cloud or aerosol in the  atmosphere, you are going to  change that amount, as well. 

 But from this chart it is  estimated that this is about  one-third of this total incoming  solar radiation.  The rest are absorbed by the  surface and also partially  absorbed by some of the clouds  by the gases and aerosols, and  after that the earth's so-called  radiation or the terrestrial  radiation and then send that  back to space.  But they can go out so direct  but they have to go through many  other processes, for example,  you also have clouds and aerosol  there.  And, again, in addition to just  merely reflecting incoming solar  radiation, they also absorb and  reradiate the terrestrial  radiation, as well.  So again there, they play a big  role in regulating the amount of  these radiation.  And if you change the amount of  clouds and aerosol and, of  course, the greenhouse gases,  then you've changed the amount  of radiation that's going to go  out and the amount of radiation  that's going to get trapped  inside the atmosphere.  So this is a very simple summary  of all those balances.  So finally you have these saying  called albedo.  Excuse me, albedo.  This albedo causes to tell you  how bright that planet is and as  we are already saying for our  little blue planet you have an  albedo about .3 or about 30% of  the incoming circular radiation  get reflected back. 

 And Venus on the other hand has  a very high albedo.  And Venus, indeed, is very  bright.  But why Venus is so bright?  It turns out that Venus  is covered by a fairly thick  layer of clouds.  Its clouds are not very dense as  what we have here.  It's tenuous but the thing is  it's very high.  And because of that and the  almost complete coverage of  these clouds, they reflect  sunlight very strongly and,  hence, you have very strong,  very high albedo.  And so albedo is the amount that  got sent back to the space  directly and the rest absorbed.  And they absorb the amount that  will be there to drive these  climate process.  And if you have less amount of  solar energy trapped inside the  atmosphere and the earth system  then -- some of them you  will have enough to drive your  climate process as vigorously as  the earth's.  Okay, so that is just an albedo  explanation there. 

 So this chart, again, is from  the IPCC AR4 radiative forcing  and uncertainties.  And here you see that in order  to make these climate  predictions and in order to make  any conclusions from what will  happen if you add more  greenhouse gases into the  atmosphere, what they do is they  run climate models.  They actually run a lot of  models and then compare  different models with each  other.  And they also make a estimate of  what are the uncertainties  involved in this.  And you can take a look at this.  The carbon dioxide is, of  course, right now thought to the  be main cause of this global  warming.  And it has as this very large  impact and it has this positive  forcing.  And this little arrows represent  the uncertainties they thought    they can estimate here.  Which is not very large.  Then you have a lot of other  things -- carbons what will be  the warming effect. 

 And a lot of other things listed  here.  But what we want to study today  is here.  This blue box here.  And this is the total aerosol  effect here.  This include the direct effect  and the cloud albedo effect.  We will talk a little bit about  this later about what are we  talking about direct effect and  the cloud albedo effect.  But you can see that in this  model they are represented by  this negative forcing.  Not only that they are  represented by this negative  forcing but the uncertainties  are huge.  So which means, for example, the  cloud albedo effect.  You can have something as small  as this or it can be as big as  that. 

 And this is almost as big as  this total forcing by this CO2.  Well, if you take all this then  you result in the warming but  you still left with all those  big uncertainties and that's why  in the IPCC AR4 they have a lot  of these terms to say that this  is probable, highly probable or  something like that.  And these are just to consider  you have such a big  uncertainties.  And this is, indeed, what we are  going to look today.  Why do we have such  uncertainties in clouds and  aerosols.  And are there any hope that we  can resolve them in the future.  Okay, so clouds.  What are the kinds of clouds?  And the short answer is there  are too many kinds.  So too many to classify but for  our purpose here I think we just  have to care about these simple  classifications.  This is a very conventional way  of meteorology classification of  clouds in terms of the heights  of clouds. 

 You have high clouds, middle  clouds, low clouds and clouds  with vertical development.  And, of course, high clouds  means they are located at a very  high level, middle clouds in the  middle level and low clouds.  And they have all numbers  associated with them which we  don't have to worry about.  Clouds with vertical development  means that cloud has a very low  cloud base but the cloud top is  very high.  So it's very difficult to say  which level they are.  Well, the importance of this  cloud classification is that all  different clouds in different  levels exert different radiative  forcing on the atmosphere.  And, hence, in order to predict  their radiative effect on the  atmosphere and on the climate  process, you really need to know  where they are.  Which level they are and so on.  And that is far from understood,  at least in the -- models.  In -- models it is, at least at  present stage, almost impossible  to do in a very realistic way of  different levels of clouds. 

 Now instead of just talking  about abstract of what high  clouds and things that we're  talking about, let's look at a  few examples of the clouds we're  talk about.  This is cirrus.  You can see that this like a  hair like structure in the  atmosphere and they are usually  very high.  Often in the upper troposphere  several thousands of meters high  there.  And they are almost all ice.  In fact, conventionally we  thought they were all ice  crystals.  Some people now say maybe a  certain amount of them are still  liquid.  But for now, at least, we think  most of them are ice.  Middle clouds, clouds like --  cumulus people used to say that  when you see clouds like this it  means there's good weather.  And I like to say that the more  accurate way to say that is if  you see that from layer of the  cloud and changing to cumulus  then weather becomes better, but  if it goes the other way then  the weather becomes worse. 

 So it's how the cloud changes  really tells how the weather  will change.  But for us here -- cumulus is  the middle clouds and mostly we  think they are water.  Then you have low clouds.  Stratocumulus and this is  currently thought to be one  important cloud to study because  they have a large area and  they're spread all over the  ocean's surface and above the  ocean's surface and, hence, they  have a large radiative impact  also.  And mostly they are water but  even though sometimes in the  wintertime you do see ice  floating out from them.  So this is an example of low  clouds.  And finally you have clouds with  -- developments.  This is cumulonimbus cloud also  called the thunder cloud.  And you can see that the thunder  cloud definitely has a lot of  rain and possibly hail falling  out from the cloud bottom.  So essentially you can see the  cloud base is already object the  surface. 

 But a cloud top in a strong  system like this, this the is it  one I ran into in 1992 in Eau  Claire and that was the biggest  nimbus I've ever experienced.  But the lower part of such a  cloud is mostly water.  But the middle and higher part  are mostly ice.  And hence, they are complicated  and what will be the real  radiative impact is something we  don't really know yet because  they all produce ice and they  can spawn a lot of these cirrus  clouds out.  Cirrus clouds, as I said, are  mostly ice.  And what will be the impact of  cirrus?  That is again a complicated  issue.  It depends not only on the level  but on where.  The low latitudes and high  latitudes impact might be  different.  So these things also consider  when people consider these  radiative forcing for climate  models.  Okay, so how do clouds form?  Well, in old days a lot of  people think that it's very  easy. 

 You have water vapor in the  atmosphere.  The water vapor would condense  into water at 100% relative  humidity.  And that's how we get clouds.  And this is wrong.  It is not so easy.  Water vapor doesn't necessarily  condense into water drop.  There's a saturation.  In fact, they're often  supersaturated.  And so that's relative humidity  100% is no guarantee and you'll  see why.  Water vapor, water drops don't  necessarily freeze into ice at  0-degrees C. 

 We have a lot of super cooling  going on in the atmosphere.  It is not like what you have in  the refrigerator that you put  water there and it will freeze  at 0-degree C.  No.  In the atmosphere, liquid water  can be as cold as minus  40-degrees C.  And they are still liquid.  So this is a very, very strong  super cool liquid there.  And so that complicates all this  process that we used to think  simple.  So what does this all mean?  Well, simply put if you don't  have aerosol you don't have  clouds in our atmosphere.  Experiments show us that  homogeneous nucleation of water  vapor, which means that you  don't have any other things just  water vapor in air, and then  they somehow condense into water  drops.  That process is what we call  homogeneous nucleation. 

 That has turned out to be nearly  impossible in the earth's  atmosphere.  You need several hundred  percents of relative humidity in  order for that kind of process  to occur.  And that's even worse.  Even if you artificially spray  water drop, if you can have such  a machine cloud making machine,  spray water drops in the  atmosphere and produce  artificial clouds.  The chemical equation will say  that at 100% relative humidity  your cloud will evaporate and  that is because clouds are water  drops, in this case, and water  drop has curvatures.  The curvature effect will be  just enough to offset a lot of  the saturations.  So for these highly curved water  drops it needs more than 100%  relative humidity to stay at  equilibrium.  So if you have 100% relative  humidity, the water drop will  evaporate.  So which means that even if you  have a cloud to begin with, the  cloud will evaporate away.  So you won't get clouds. 

 So what do you need?  We need heterogeneous  nucleation.  This means that you do have some  other chemicals present in these  configurations so that water  drops or ice crystals can form.  And that is the so-called  heterogeneous nucleation  process.  Aerosol particles, in this case,  serve as the nuclei for  condensation and the freezing to  occur.  So, in other words, these  aerosol particles in the  atmosphere they not just hanging  there doing nothing much they do  a lot of important chemical  impact.  And for the most they form  clouds.  So what are the type of aerosol  particles that can serve to  condense and freeze those water  substance.  Well, first of all, we have one  kind called cloud condensation  nuclei.  We abbreviate as CCN.  CCN particles that help forming  cloud drops. 

 They're usually chemical is that  they have to be hygroscopic.  They can absorb water easily.  They don't have to exactly  dissolve in water.  So they don't have to be water  insoluble.  But they have to be hygroscopic.  And examples of these  hygroscopic particles are like  sea salt particles or ammonium  sulfate.  These are all hygroscopic  particles.  And ammonium sulfate is probably  the most prevalent CCN in the  atmosphere.  And in principle, we think that  you have one CCN forms one cloud  drops in clouds.  And later when the drop collide  and form rain drops, that's a  different story. 

 But in the formation stage of  clouds we conventionally think  that one CCN forms one drop.  Then there is another kind of  particles it's called ice nuclei  and abbreviated as IN.  These are particles helped  forming ice particles.  And we don't really know very  much about the properties of IN  yet.  We know something but we don't  have the complete knowledge.  We know that they better be  hydrophobic.  In other words, they cannot be  dissolved in water and repel  water.  For an exact reason, we don't  really know.  And examples of ice nuclei  surprisingly silicates, this is  a very common particles.  Clay. 

 Clay particles in the low levels  can serve as ice nuclei.  And people think that, oh, that  means that we have abundant  source of ice nuclei.  The answer is no.  Most of the clay particles are  very large.  They will not become airborne in  high place.  In order to produce ice, you  need to have those particles so  be in the upper troposphere.  So how do you get those  particles higher up there is one  big question.  It turn out that a lot of these  high-end and especially landed  in this country here came from  places like Mongolia or China  where you have big dust storms.  They carry up a lot of these  particles in high atmosphere  transported thousands of miles  and finally fall down in the  upper troposphere and promote a  lot of ice formation in our  events here.  There are also other particles,  organic particles, that can  serve as ice nuclei. 

 And one is in a bacteria that  infect some of the trees here.  In the fall time just like eight  months ago we have this  beautiful fall color.  One of the factors influence how  early or how late those fall  color appear is they are  infected by this bacteria and  there is a little particle in  this bacteria that serve as ice  nuclei to promote formation of  frost.  If you have a lot of this  bacteria you get frost earlier  and possibly you get very nice  fall color early.  And if you have less than that,  well, it's probably come a  little later.  And the UW turn out to be one of  the interesting place that  initiated those ideas and  actually commercialize a lot of  ski resorts actually harvest the  nuclei for the production of  artificial snow for the ski --.  Number of ice particles turn out  to be greater than the ice  nuclei due to another process  called ice multiplication.  So unlike the CCN, which we  think one CCN will produce one  cloud drop, the IN is a smaller  number and they produce more,  sometimes many thousands of ice  crystals.  Due to a process generally  called ice multiplication and at  this stage we don't even  understand very well what this  ice multiplication process  really is.  So there already are a lot of  unknowns in this cloud process. 

 To show you how difficult to  form water drop in the  atmosphere, this is a slide that  from an experiment I performed  when I was a graduate student.  So that was about almost 30  years ago or something.  What I have here is I tried to  understand what causes the water  drop to nucleate.  And you can of course throw in  all kinds of particles there.  And I tried to do a clean case.  So I took as a sort of  semiconductor it's called --.  You can touch a battery to it so  that you can have change the  potentials in the electro field  there and I want to know what  effect the electro field will  have on the formation of drops.  And this is under the microscope  so it looks very large.  But actually this is talking  about a micron size.  Here you have so-called P type  and N type. 

 And P type is -- and is N type  is doped with phosphorus.  And I put this whole thing on a  cold stage.  So I turned on the cold stage  and keep it cool and become  colder and colder and then I  passed some water vapor over it.  And this is the stage you will  see the water drop appear.  And that is a way I studied this  nucleation.  And I usually have to cool it  down to minus 10  or minus 20-degrees  so you can see any drops.  Not ice.  This is just water drops.  It just to say that ice forms  even more difficult.  But it just from this slide you  already see that the P type  seems to form drop easier and  the N type doesn't seem to form  drop very easily. 

 And, indeed, even now we don't  completely understand why that  is the case.  So this is something worthwhile,  again, to study.  And when I turn on the electro  field, when I touch this whole  thing to an external voltage  supply, the drops form  especially rapid along the  boundaries between the P and N  type.  To apparently the high electro  field helps forming these drops.  In all this process very  interesting and all the while I  have hard time to really form  ice crystal directly.  The ice crystal always form  after the drops appear and then  they freeze into ice.  Theoretically, we thought that  ice crystal if it's cold enough,  ice crystal would just appear by  themselves without going through  liquid stage.  But no, they always seem to go  through that.  So exactly how ice crystal form  in the atmosphere is a big  enigma now.  We don't know. 

 It's something nobody really  knows.  We guess, we have a lot of  theories but we don't really  know.  So that's just one example to  show what we don't know.  Okay, if you look at different  types of aerosol particles,  they're bound to have different  kind of electro properties on  the surface and that will have a  lot of impact on how and what  kind of capability that they can  nucleate water drops and ice  crystals.  Let's take a look at the sources  of aerosol particles.  Briefly, first of all, you have  mechanical disintegration of the  earth's surface materials.  So wind blown dust is one of  them.  You have some other processes  withering of rocks and things  like that that can produce all  those small particles and become  airborne.  That's one source.  Combustion, you have forest  fires, prairie fires. 

 We have a lot of these  summertime like in California.  And you hear about those big  fires in San Diego and  Los Angeles areas and all those  places produce a lot of  particles.  The third is the GPC, the gas  to particle conversion.  You have vapors condensed into  particles.  Well, vapors of one kind and the  other mixed together through  chemical reactions that can  produce particles.  They usually put it as very,  very fine particles.  Volcanoes definitely also  produce particles.  Volcanoes inject a lot of  particles into, not only the  troposphere but also into the  stratosphere and they can stay  there for many, many years.  Extraterrestrial sources, you  have meteors coming to the  atmosphere and at high speeds  and they burn up into small  particles and leftover a lot of  these tiny particles in high  atmosphere.  Finally, you have this big  source called anthropogenic  source, this is human related,  human activities, industrial and  what not, produce also a lot of  aerosol particles. 

 And they all have different kind  of properties.  If you produce particles in the  atmosphere, you must have some  way to take them out.  Otherwise they will accumulate  more and more in the atmosphere.  And that is one of the worries  these days is the atmosphere  have enough capability of  cleansing itself.  And that is the big question.  What are these things?  Well, basically we thought that  there are two main categories.  One is called the dry removal.  The other is called wet removal.  The dry removal process involve  processes like gravitational  settling.  Particles are heavy and then  they settle by this  gravitational attraction and get  removed from the atmosphere. 

 If a wind carry a lot of these  particles through buildings  forest, they get collide and  they get removed from the  atmosphere by filtering through  these structures.  Coagulation of particles,  particles collide with each  other, become heavy and they  fall out.  So that is considered as a  separate category.  Brownian diffusion, this is just  by the fact that the small  particles can get bombarded by  air molecules and so they move  in a chaotic way so they get  removed by colliding with other  surfaces and they get removed.  So these are the dry removal  process.  Wet removal are those processes  involved in clouds and  precipitation process.  And for the most is nucleation.  Which is talk about how aerosol  particles serve as the formation  of cloud drops and ice crystals.  And that nucleation is currently  thought to be, by far, the most  efficient process of removing  those particles.  And that has a very important  implication to the climate  process, as you see. 

 The other is the collision with  cloud particles.  The cloud particles here I have  broader definition of cloud and  precipitation particles.  When these particles collide  with them, they get removed by  falling out with the rain or  snow.  And so become removed that way.  And we have another name called  the precipitation --.  This will represent the  collision with cloud particles  and aerosol particles and they  fall out of the atmosphere.  From all the studies we know now  clouds and precipitation are the  number one cleanser of the  atmosphere.  This is, by far, the most  efficient one.  If you have enough cloud and  precipitation process then it is  possible to remove those  particles from the atmosphere.  But they are not so easy to get  removed it turns out. 

 This is from a slide of my PhD  work is to study quantitatively  how fast particles  can be removed by rain.  It turn out that some particles,  yes, some particles can be  removed efficiently.  And what you see here is a  chart, vertical access is the --  efficiency.  You can loosely think that this  is the removal efficiency and  horizontal is the particle  radius.  Various small particles on the  left-hand side can be removed  efficiently.  You can see that their efficient  is relatively high.  Ten to the minus one for this  particular drop size, about  100 micron or so.  So one out of ten particles can  get removed when you're small.  And when they are very large,  larger than 10 microns or so,  they also get removed easily.  There is a category of particles  somewhere between  .1 and 1 microns. 

 They are almost impossible to  remove.  One per thousand or one per ten  thousand of them get removed by  rain.  And that becomes very difficult.  The removal efficiency is very  low here.  And this particle of this size  range is sometimes called, the  particles belong to this  so-called Greenfield gap.  Greenfield used to be the EPA  director and he was the first  one to predict that there should  be such a gap exist.  And what I have done is  quantitatively prove that, yes,  he was right that indeed you do  have such a gap.  And so here just to say that if  you have electricity then you  can remove them a little more  efficiently and so on.  But in general they are very  difficult to remove.  Ironically, these are the  particles can get into your body  easily. 

 >> How did you go about getting  those data.  >> This is by experiment.  I produce aerosol particles  myself and I produce my own rain  drops.  Simulated rain drops.  >> Atmosphere it's contained.  >> It's contained.  It's about one hundred feet high  or so.  And on top of this one hundred  feet I generate water drops.  Then they go through this  contained aerosol column which I  produced also by myself.  And then I collect those aerosol  particles and measure them using  nuclear reactor because they are  very small, ten to minus ten to  minus 11 grams. 

 And so using that you can  measure that indeed it's very,  very small amount.  >> Thank you.  >> You're welcome.  So there is such a thing that's  very difficult to remove and  they can get into your body,  ironically.  Particles large enough will be  stopped by your hair in the  nose.  Your nose is a very good filter  for that.  Particles very small can get  into body but they can get out  very easily because they are  small.  Right in this size it looks like  our lungs will be able to keep  those particles there.  So those particles between  .1 and 1 microns are staying in  your lungs once they get in.  And that is one of the danger of  those particles. 

 And this is precisely particles  that you have a maximum amount  in the atmosphere also.  There are a few -- there.  And this is one of the --.  This is particles in the  atmosphere we say X amount  concentration.  Okay, so finally we have this  cloud and aerosol interaction  and their impact in the  atmosphere, and this is the main  point we are going to look here.  This is also from IPCC AR4.  What you see here is that there  are several different kind of  effect they are talking about.  The first is the direct effect.  Suppose you put a lot of aerosol  into the atmosphere, what will  be the direct effect?  Well, direct effect causes that  they are scaring in absorption.  And that again depends on what  kind of aerosol you're talking  about. 

 Some aerosols are good at  scaring; some are good at  absorption.  If they are biocarbon then he  absorb easily.  If they are shining particles  and very tiny particles they are  good at scaring.  It also depends on which level  they are.  So all these things play a  complicated role and we just  begin to understand what  aerosols are doing to the  atmosphere.  It is one of the effects that  was overlooked in the beginning.  In fact, the IPCC forgot about  this aerosol effect in the  beginning.  It turned out to be it may have  important impact.  But this is the direct effects  of the aerosol particles by  direct interaction with the  solar radiation.  But they have indirect effect,  as well. 

 Indirect effect is majorly to do  with cloud formation.  This one here shows the  unperturbed clouds.  In other words, if you don't  have a lot of aerosol there, in  fact, this is a little ironic  because you do need to have an  aerosol to begin with in order  to form clouds.  And we thought that what we're  talking about those natural  cloud before all those global  warming things.  So let's say clouds back in the  16th century or 15th century  these kind of nice clouds, they  have a normal cloud drop size.  So you form clouds, they collide  and form big drops and they fall  out.  Now you have some indirect  clouds.  The indirect effect, sorry.    What will happen if you  introduce more of those  condensation nuclei that's the  CCN or CDNC here similar to  that.  Keeping the liquid water  content, this LWC represent  liquid water content constant. 

 If you introduce more nuclei  into clouds, then you form more  drops.  But because the amount of water  is constant, each drop is very  small.  And when the drop is small, they  are very sustainable.  They are -- stable.  And they won't collide easily.  And a result collision you don't  form rain drops.  They don't fall out.  They will stay there longer,  actually.  One possible scenario of this  injecting more aerosol particles  into the atmosphere is that you  may increase the total amount of  clouds.  You may decrease the amount of  rain fall because the cloud will  be thick, but they don't fall  out because drop size are small  and the precipitation becomes  smaller. 

 So this is one of the first  effect and not only that, small  drops, a cloud weighs a lot of  small drops as opposed to a  cloud weighs smaller number with  larger of size will have higher  albedo.  They can reflect sunlight  stronger.  And this is precisely the case  of Venus.  Venus has a lot of these small  drop size clouds.  And the Venus look shiny from  outer space.  They have a very high albedo.  So this is the effect called  first direct effect.  And this is first pointed out by  Sean Toomey in 1974.  Then you have other so-called  second indirect effect.  And this is all have something  to do with the lifetime of  clouds. 

 And I have just talked about is  if you have a smaller drop size  then they are collidibly stable,  they won't form rain and they  tend to hang on the earth for a  longer time.  And there's one possible effect  also that is not so obvious here  is that these drops are formed  by more of those aerosol  particles.  Some of them can be dissolved in  water.  And once you have these aqueous  drops, we know that they require  less water vapor to stay in the  atmosphere so they their staying  power in the atmosphere becomes  stronger.  You know, dirty water is harder  to evaporate and it can stay  there longer.  And that will be the case in a  larger city you can form those  haze and clouds and they tend to  stay there longer.  Why?  They don't evaporate easily  because they don't need as much  water vapor to stay saturated.  To stay in equilibrium.  So that all plays a role in  these called the lifetime  effect.  So these are water drop clouds  and you have also some effect of  the ice clouds but we are not  prepared to discuss that. 

 But anyway, you can see that  there are already direct effect  of aerosol particles and  indirect effect of aerosol  particles and many play through  this cloud process.  >> What's the mean lifetime of a  cloud?  >> Depends on the type of cloud  that you're talking about.  High clouds, for example, have,  in general, a few hours there.  There are some high clouds in a  very cold place that have been  reported to stay there for  several days.  Which I haven't seen that by my  eyes so I'm not sure whether  such reports are correct.  But it's not impossible in that  in a very cold temperature ice  crystals evaporate very slowly  because the saturation vapor  pressure is very low.  And, hence, they stay there for  a long time.  And that is one possibility.  For thunderstorms, for example,  some of the thunderstorms finish  in about an hour or so.  But some are called supercells. 

 These last for days.  They travel from one place to  the other.  So it becomes hard to say what  is the lifetime.  They just keep going and going  and going.  So it depends on different  situations.  Okay, this one is talking about  a direct, well not direct but a  visual comparison of the aerosol  impact of the Brazilian biomass  burning.  These are from NASA.  This picture shows that in a  clear day without forests  burning you can see all through  to the ocean surface.  You can see those dark places is  the ocean surface out of --  Brazil.  But when you have forests  burning you can see the same  area is very small. 

 And you can believe easily that  the albedo impact, in this case,  is very strong as compared to  this.  So indeed, human injection of  aerosol particles into the  atmosphere would be very, very  strong given cases like this.  There are more uncertainties.  One of the findings that we  found recently is that clouds  actually can be more complicated  than conventionally thought  about.  Conventionally we thought that  the cloud is merely a response  to the climate.  So it is not considered as a  forcing.  Mainly it's because people  thought that in the time of a  year you have cloud, you have  water vapor formed and then they  fall out.  So the evaporation amount and  precipitation amount even out.  It won't be the case if the  water vapor get into the  stratosphere.  Which we know stratosphere  usually is very dry. 

 But for some strange reason in  the last 30 years or so the  water vapor has been changing,  mainly increasing.  Recently it seems to decrease a  little bit.  But even the fact that the water  vapor is changing amount is  already causing some kind of  alarms.  Why do water vapor increase in  the stratosphere?  In the stratosphere the resting  time of water vapor is more than  is year, possibly a few years  and that will be a climate  forcing.  And that has not been taken into  account by any of the climate  models.  And the radiative impact of  water vapor in the stratosphere  with be hundreds or maybe  thousands times stronger than  they are in the troposphere.  Fact that they do get into the  stratosphere is showing like  this.  This is a very strong  thunderstorm in Spain.  Usually this is satellite  pictures and this is the --.  We see that you have this  chimney like plumes  on top of the --. 

 It is already at the -- and this  is about three kilometers higher  than the --.  This is in the stratosphere.  Initially we thought that this  maybe occasionally occurs.  But no, the more we look into it  the more they are.  And this is another case.  Chicago is somewhere here and  this is the big storm over  Chicago in 2004.  And soon this storm moves over  Madison.  And I happen to look at the  MODIS satellite pictures and  found out, wow, look at these  big plumes on top.  There's no doubt that these  plumes are in the stratosphere.  So they do get into the  stratosphere. 

 And I have a theory to say how.  My theory is -- since all those  water vapor into the  stratosphere.  And what kind of impact they're  going to have to this climate  process is something we don't  really know presently.  But human impact, by far, is  probably the most linear.  You give human good weather and  they would like to live there  and they produce a lot of things  like this.  This is Los Angeles.  One picture I took this summer  when I was approaching the  airport and couldn't see a  thing.  Well, the number of particles  can be easily millions per cubic  centimeter, per CC.  Huge amount of aerosol  particles.  This is Tokyo. 

 Over Tokyo.  You can see distinct two layers.  Above here, nice clear  atmosphere with a lot of  beautiful white clouds.  And below, nice and brownish  particle haze layer down below.  That is how human do to the  atmosphere.  You produce particles.  You change the behavior of the  atmosphere.  You change the behavior of  clouds.  And there are more to come.  In Asia now you have a lot of  this industrialization. 

 These are MODIS pictures from  China and India.  Both shows very strong aerosol  generation into the atmosphere.  You can see that every day from  the MODIS pictures almost.  And right now the European  nations has a project called  Atmospheric Brown Clouds.  For short called ABC project to  study these brown rain clouds.  And, in fact, I have seen these  pictures many, many years ago  and interesting history I want  to locate some of the historical  forces.  And I couldn't find it.  There's no clear pictures.  Always hazy, always smoky.  It turn out to be that's the  case. 

 And so you now you have this  project going on called ABC.  So that is the end of my talk  and just to say that aerosol and  the clouds have such an impact  on the climate process and we do  not have complete knowledge of  them.  They're still a lot of unknowns.  Thank you, very much.  (applause)  >> Thank you for that  interesting talk.  We have time for a few  questions.  >> What is your own  recommendation about control of  aerosols and how we might have a  mitigating effect on their  climate impact?  >> Yes, there are indeed many  different issues involved.  There are technologies, in order  to control them.  One of the main source of  aerosol particle is a sulfate.  When you burn coal, you produce  sulfur dioxide and eventually  they turn into sulfur particles  by reacting with moisture in the  atmosphere. 

 Countries like Japan they have  desulfurization in the  atmosphere and they can take  some of those gases and decrease  the amount of particles in the  atmosphere.  But it's not cheap.  It's expensive.  And it's precisely a lot of  these large developing countries  with huge populations they don't  really have a lot of money to  buy those technologies.  So that is just scientific  issues these are more like  political and social issues  there.  So recommendations, yes,  technology should be there and  to help but how to implement  those technologies is something  I don't know.  >> So alternative fuels other  than coal would be helpful.  >> Yes, but that again is again  the cost problem.  Coal is cheaper compared to oil  or natural gases and how to make  those more expensive fuel  available to those less affluent  countries is another problem.  Please. 

 >> The Arctic Ocean has been  melting back in the '70s and  earlier was basically frozen  most of it was frozen year-round  with rather thick ice.  And now it's melting.  And I'm wondering what's  happening to that stratosphere  and so forth above the Arctic  because it's been in the last  ten years.  >> It's very interesting.  Recently there are a lot of  studies about Arctic haze and  also some of the aerosol  particles occur there.  It's somehow related to what I  just talk about breaking process  that we are talking about.  Conventionally we thought that  nothing can occur over the  Arctic because there are too  many strong convective storms  occurring there.  Well, it turned out that once in  a while you do have a lot of  fires occurring there.  And this fire will produce a lot  of particles.  Now, conventionally, people  thought those particles will get  up to a few kilometers and then  they'll come back. 

 Not so.  Sometimes they actually produce  thunderstorms from them.  And through this so-called --  breaking process they actually  penetrate the -- and get into  the stratosphere and then they  spread over Arctic regions and  we've seen that in satellite  pictures.  And so this may contribute to  this, aside from the CO2 warming  that everybody knows that,  these particles also go in there  and also may contribute to this  process, as well.  And there are some studies now  in these transporter particles  over these Arctic places.  >> Do you want to comment on the  fairly recent proposal that  perhaps we should put additional  aerosol shield over the earth  and use that to counteract the  global warming that's occurring  because of carbon dioxide.  >> That is, in fact, always some  people tried to suggest that.  For example, I remember that  what we had this ozone hole some  industrial people says that why  don't we just have an airplane  and spray some ozones into the  stratosphere to produce it.  What they forget is people  always thought about this  averaging process.  On the average if you put this  into that then you can even it  out. 

 But no.  Atmosphere doesn't work that  way.  First of all, you have to worry  about the time scale and the  space scale.  What you produce here may end up  just involved in the local scale  things.  So if you produce an aerosol  here, you produce a lot of small  scale already locally.  And indeed, for example, if we  have warming over the ocean  surface and then you have this  cooling over the land surface  you already create another scale  circulation there.  That may influence the local  climate already.  And this may not be what people  think even out in the long run.  No, actually it may contribute  to the more variance of the  climatic change.  So instead of even out things it  may cause a lot of fluctuations  in the climate. 

 And is that going to be good or  bad?  We don't know.  So I do not recommend  experimenting climate like that.  Please.  >> Have you found the chaos  thinking or model or other  complex models useful for your  work?  >> I have not take that into  account and, in fact, I have to  learn more of those things that  may be coming to the series  more.  I want to talk to Clint more  about that.  But I'm sure it will be helpful  because obviously these are very  non-linear and there may be some  chaotic patterns we can also  learn.  >> One last question.  Russ?  >> Have deserts been increasing  or changing as a contributor to  the factors you talked about?  >> I have read some literature  saying that deserts in China  actually expanding.  What kind of impact that result  is such expansion is something  we don't know.  There are some saying the human  development, the local  development, deforestation, for  example, is possibly a big  factor in expanding of the  deserts there. 

 But I'm not expert there so this  is just what I have read.  >> Well, I'd like to thank you  for a very nice talk and  thank you all for coming.  (applause)