Air Pollution and the Climate System: Sustainability Now and Later

– So, well, sustainability is always now and later So my talk is a little bit of a misnomer or the title is Let me start off with what I want you to take home And the first thing is that climate change is more than just a greenhouse effect There is the greenhouse effect, but there’s more to it than that, and I’m going to show you some of that The second thing is that, small emission sources matter A lot of times when we think about climate change, we think about big power plants and big smoke stacks, and the solutions are solar power everywhere and nuclear power And that’s true, that’s true, but there’s more to it than that, again And the last thing is that a there’s a broad portfolio of solutions available, and we need to think about when and where and who is affected as well as just the broad, reduce greenhouse gases So that’s my message to you, is think a little more complicated terms (clears throat) I’m a scientist, I like to complicate things I’m gonna start with talking about human effects on the earth radiation balance Greenhouse gases, yes, but also particles And then I’m gonna go into a special case, carbon particles Little, tiny particles, much smaller than your hair, and the role of very small emission sources And number two is really what my research group works on So that’s gonna be some of my things And then the last is more of a discussion and I’d be happy if you participated How do we balance near-term and long-term goals Usually when we’re thinking about the climate change picture, it’s a very long-term picture What might happen in 2050 or 2100 And we have to start thinking about that now But we also have goals that occur today, and in a few years And so, that’s what I mean when I say, sustainability now and sustainability later We have the needs of the present and the needs of the future So, first of all, what are we doing to the earth radiation balance? I’m seeing people turning off their phones, and I’m just realizing that I didn’t do that to mine So if my phone goes off, you can shoot me Okay, this is what I call our fire dilemma We like it, we love fire Anyone not like fire here? We like it and we don’t like it So it’s warmth and after a while it became sterilization, that was one of our processing, one of our first uses Power, mobility, we love to sit around bonfires We love to stare at them and feel spiritual And yet the fires have a lot of hazard; poor air quality there, their effluence create health damages And now we’re talking about global change from the emissions When we think about climate change, usually we think CO2, right? And it’s funny because for a long time engineers really tried to make CO2, that was the goal You want CO2 to come out of combustion If you’re not putting CO2 out of combustion, you’re doing it wrong So, climate change is really a successful engineer’s problem We did it right and now we’re making so much CO2 that it’s affecting the atmosphere But there’s incomplete combustion products that occurred before engineers were really good at it And those also affect not only the environment around us where we can see it, but also climate change So, these Whoops, oh, no, that’s the one I wasn’t supposed to push Okay All right, climate change CO2, yes, affects climate change But CO2 doesn’t really cause outdoor air pollution, at least not that we can see It doesn’t bother us, we don’t think of it as a big urban problem It doesn’t cause indoor air pollution Well, yes it does We don’t want the CO2 to be too high, but there’s nobody struggling to see through clouds of CO2 when you’re burning inside This other gases, products of incomplete combustion; carbon monoxide, volatile organic compounds, methane and particulate matter, which I sometimes abbreviate PM, those are the things that we’ve struggled to avoid for decades or centuries And so those first create indoor air pollution People who burn fuel inside, it happens It happens in developing countries It happens here

when people have less visible affluence but there’s still interior combustion Okay, so these are emitted into indoors or outdoors And that’s what we think of as our air quality problems And so, we’ve tended to lump these things into indoor and outdoor air pollution; health problems, visibility problems We don’t like that, let’s clean it up But we haven’t really said and these are climate changes too We’ve tended to separate air quality and climate change into two different things The stuff you can see, the stuff that bothers you, odors, near-term problems around you, they don’t spread out very far And then this the good engineers problem, CO2 is a climate change problem But all of those pollutants actually cause climate change So here is a graph that you’ll see many, many times from the intergovernmental panel on climate change This is the latest assessment report And the magnitude of the bars on this side, indicates that that’s how much air pollutant is contributing to warming And if it’s on this side of the line, it suggests that that is contributing to actually cooling climate So the biggest one, sure enough, is CO2, that’s why you hear about it so much And there are other greenhouse gases, methane, but carbon monoxide, which could be an indoor air quality problem That’s why we have alarms for it in our homes Some people intentionally burn indoors especially in developing countries So that could be an indoor or outdoor air quality problem There it is, it’s got a little bit of a warming effect And here’s NOx, nitrogen oxide, a little bit of a cooling effect Here are sulfates that come out of sulfur from coal Something that people work on a lot to reduce sulfur emissions, so that we don’t have outdoor particulate pollution And yet when those things escape to the atmosphere, they turn into particles Particles reflect light, bounce it away And so less sunlight’s coming into the earth, cooling They change clouds, cooling And here’s a black sturdy stuff, warming So out of this one fire, greenhouse gases, a lot of them warming, other kinds of gases, warming and cooling, and particulate matter, mostly cooling but a little bit of alarming So, everything that comes out of fires, is actually having a climate effect, even though most of what we worry about is CO2 Yeah (indistinct) – [Lecturer] I hate when people make things complicated – [Student 1] How? What makes the CO (indistinct)? – [Lecturer] You mean this for example, or these little, these little slices, is okay So this is emissions of carbon monoxide I’ll just take one example and then maybe we can talk about the other ones later Emissions of carbon monoxide have an effect on earth radiation balance, not because carbon monoxide absorbs a whole lot of light, it doesn’t But it does affect the chemistry of the earth by increasing the lifetime of methane, So that’s CH4, by causing tropospheric ozone, which does absorb energy and dump it into the atmosphere So these little slices are the different effects that that particular gas has, and the same can be done with NOx, we can go over that later Anyone else feel free to jump in, if you have questions or don’t understand something Particulate matter, doesn’t get very far, does it? Right, it’s just around the cities, and once you drive away from a city like Chicago, the air gets clear Well, maybe, maybe Hey, this is a continental By now we’re emitting enough that you can see the plume of pollution coming off North America Here we’re showing a hazy air off the South Asia, so Indo-Asian haze, thousands of kilometers into the Indian ocean, Atlantic ocean, and even reaching other continents So particular matter which used to be an urban air quality problem, no longer is Here’s another picture

This is the coast of Asia And we pick on Asia a lot, cause it has a lot of people, but this is actually true of every continent that has some significant energy use And what you can see here just barely, it’s a little bit bright, can you see that? And if all the lights were off, you could see it even better So here’s particle emissions coming off the coast of Asia And why can you see them? Why can you see them? You can see them because they’re a different color over in the ocean And if there were a different color over in the ocean, it means they’re reflecting differently than the ocean does So that means they’re changing the way the earth reflects light This plume here is even more dramatic What’s happening here, is that particles are coming from the continent and they’re taking up water, they’re interacting with clouds So clouds that might not be there or that would look different without those particles being emitted, are changed The emission of particles changes the earth’s reflectivity And that means that particulate matter has an effect on how much energy gets to the earth And it plays a role in the earth radiation balance just as carbon dioxide does So- – [Student 1] Can you (indistinct)? – [Lecturer] That’s the way the wind blows – [Student 1] I’m sorry – [Lecturer] That’s the way the wind blows So I’m gonna be a little more specific about three different things that come from combustion Carbon dioxide, which the Sun’s visible rays come in and then carbon dioxide helps to trap infrared radiation coming back from the earth I assume most people know that, but if you want me to explain it further, I’m happy to do so after the seminar Sulfate particles, here’s what they look like if you look at them under an electron microscope They’re very small, they don’t look that way here But they’re, again, bouncing the visible radiation away So, sunlight comes in and bounces right away So this is not an infrared radiation question And then soot aerosol, which you’re probably all familiar with from looking at fires or playing with candles Somebody here will admit that they didn’t play with fire when they were a child I won’t tell your parents And what happens with black carbon? Soot? Is the sunlight comes in, that’s black, so it absorbs radiation You all know that from walking across a hot asphalt on a hot day or wearing black clothing, absorbs radiation turns it into heat, dumps it in the atmosphere So we’ve got one thing that’s warming the earth by absorbing, infrared radiation One thing that’s cooling the earth by bouncing away visible radiation, and one thing that’s warming the earth by absorbing visible radiation, sunlight, three things (indistinct) It’s usually ammonium sulfate, it is the sulfur dioxide from coal combines with ammonium in the atmosphere, they’re not emitted together But people usually call it, colloquially, sulfate, because will be something sulfate based on how much SO2 is emitted Massoud, are you asking a question or you’re just waving a finger? (indistinct) Okay (clears throat) They have very different sources, these three, carbon dioxide, sulfate and soot Carbon dioxide in metric tons per year, is by far the dominant emission There’s a lot of carbon dioxide and not as much sulfate and even less soot So maybe we don’t have to worry about that little stuff, there’s a lot of carbon dioxide Why is it emitted, carbon dioxide? Again, you can’t help it Fuel has carbon in it, we wanna turn it into carbon dioxide, out the stack, it goes so far until people learn how to sequester it Sulfur in fuels, if it’s not captured, again, out the stack and it turns into sulfate in the atmosphere Soot why does it happen? Bad combustion You can burn a carbon-based fuel all the way to carbon dioxide and make almost no soot at all

But that doesn’t always happen, we’ll talk about that in a bit There’s also very different atmospheric lifetimes and this is important Carbon dioxide might stay in the atmosphere for a hundred years And so, once you put it out, it’s out there, and you’re stuck with it That’s why people are worried about climate change because the stuff that we’re admitting today is going to be there for our grandchildren and their children And they didn’t ask for that Sulfate aerosol and soot aerosol would be gone in a few days, because they get rained out You know how much clearer it is after a rain? This is another reason or a big reason why people don’t talk about them when they talk about climate change Because if we stop emitting particles right now, in a hundred years, they’re gonna be gone In fact, next week, they’re gonna be gone So it’s not a long-term problem, but it is still happening Yeah, here’s an interesting thing, how much does one kilogram of the stuff in the atmosphere affect the earth energy balance? For carbon dioxide, is about one watt per gram in the atmosphere For a sulfate, it’s about 200 And for soot, it’s about 1800 watts per gram in the atmosphere So that’s, if you take a gram of soot and get out in the atmosphere, it’s like running a space here in the atmosphere, just a gram Why is it so strong? Because it had absorbs everything that hits it It loves radiation Carbon dioxide will absorb it a few wavelengths But particles interact with visible radiation very well So, they’re going to be gone, and they’re not as high in emission, but they’re really strong Something about confidence, we have pretty strong confidence, and perhaps in not what will happen to the carbon dioxide, but certainly in what it does when it’s in the atmosphere For the for the particles, we don’t know quite as much It’s harder because they’re poorly mixed So the concentrations are high near sources and low far away from sources, and it’s just hard to study the average effects So if you increase carbon dioxide, you get warming If you decrease sulfate aerosol, you got warming Wait a minute, don’t we want to decrease sulfate aerosol? Chris, you’re saying no (indistinct) What? (indistinct) Oh Oh, dear, now you’re getting complicated Most of the people in this room would like to see probably fewer emissions that resulted in particles that then caused health damage So a lot of times we, in the simple case, chemistry aside, we would like to reduce sulfate particles And there are solutions, right? Use energy with less carbon, carbon dioxide is not so easy You can use fuel with less sulfur You could put end of pipe controls on everything There are solutions, the ones for carbon dioxide are hard The ones for the others are maybe not cheap, but not as hard So we’ve got a bunch of carbon dioxide in the atmosphere, and we’ve got a bunch of sulfate particles in the atmosphere And that means that we’ve actually emitted a bunch of carbon dioxide, and we should be seeing a lot of warming, except we have this reflective blanket of sulfate particles which has prevented that warming from taking place, ’cause we keep emitting sulfate particles Right? They may go away very quickly, but we keep putting them out there every day, all the time And so, some of the warming that we should have seen, we haven’t seen yet because we have that protective sulfate up there keeping the sun’s energy out Well, isn’t that nice for us? Many people want to remove sulfate aerosols And so when those are taken away by air quality regulations,

and they will be, that’s being worked on, that mask is going away, and the CO2 that we put in the atmosphere will still be there, because it’s going to be there for decades So, even if we stop emitting CO2 right now, and stop emitting sulfate right now, we’re stuck with the CO2 And as soon as the sulfate goes away, it’s going to get hot, even if we do nothing else to emit CO2 There are people who are already concerned that, we don’t quite understand going on with the climate And this graph is showing different tipping points that could occur with different amounts of warming On this axis is degrees centigrade, and here’s things that could happen Arctic ice could be gone in the summer, oh, it is very close to gone in the summer And then there are different ice sheets that could melt, and then out here you start affecting circulation We’re not here yet, but there’s a lot we don’t know about models But this blue line indicates the range of warming not in 2015 and 2100, the range of warming people think we have committed to by putting carbon dioxide in the atmosphere The stuff that’s out there today, right now, is perhaps in this range And when I say, perhaps, it’s that different models produce different amounts of warming, so we don’t quite know But the range of committed warming, bound some of the tipping points, but we’re not really sure we want to experience Here’s what we have now, realized warming This is the warming we’ve seen When the sulfates go away, and when the ocean comes into equilibrium, this is the warming that people think we will probably see So all of a sudden climate change is not, “Oh, we better do something by 2050 and get our emissions under control.” We’re faced with a challenge right now We’re already in the boat It’s in the middle of the ocean We got to figure out what to do For some products or for some sources that are admitting a little bit of CO2, we’ll talk about these really soon, and a lot of products of incomplete combustion, the greenhouse gas measure is a poor measure of the climate impact I can show you this figure for a power plant that’s emitting sulfate, and it might look like it was net zero in terms of climate impact But what I’m going to show you is what I’m gonna talk about next And this is a small source whose combustion it’s so bad, it’s something a little bit of greenhouse gas, cause it’s small and a lot of products of incomplete combustion, many of which contribute to warming So, if you look at these bars, you don’t have to understand the numbers I’m not going to take the time to explain them And I’m happy to do that after the seminar But what I want you to see, is how big this bars are, compared with these dotted bars In some cases, these bars are smaller, but significant This bar is bigger than the carbon dioxide bar There are ways of burning things where the climate impact is not in the CO2, it’s all in the products of incomplete combustion And this hundred year tag that I’ve put on here, is the amount of energy added to the climate system over a hundred years So it doesn’t matter that these things go away It doesn’t matter that the particles go away or that carbon monoxide only lasts a month In that short lifetime, it adds as much energy to the climate system as the CO2 from that source over a hundred years So it’s like a big bang of energy And yet, if you look at these sources, the way people do when they’re doing a carbon footprint, carbon footprint, oops, is counting that bit So you could choose this source and say, “Oh, look, I don’t have any carbon footprint.” But you’re still making a big bang in the climate system So, lesson one, there’s a lot of pollutants

affecting climate, it’s bigger than just greenhouse gases Okay, this is where I get to talk about my stuff There’s a lot of kinds of carbon, many atmospheric chemist split them into two kinds of particles; scattering particles and absorbing particles And I already showed you this where the scattering particles were sulfate, there are also carbon particles that scatter light So the big difference I want you to notice is that there’s particles that absorb light and warm, particles that reflect light or scatter it and cool Most particles cool the climate system, this special one called black carbon warms it Reduce black carbon, warming comes down Where does this stuff come from? These are pies for black carbon, and I don’t have a legend on the pie for the non black carbon, the organic carbon Chemists hate this term, I’m sorry about it But we call everything that isn’t black, organic But let’s just look at the pie here, where a lot of it comes from a lot of open burning This is a global picture So that open burning takes place in South America and Africa in what we call boreal forest, Canada, Russia What could we control, if it’s good idea to reduce warming particles? What could we change? There’s a big piece of the pie from road transport and non road transport tractors, and so on So that’s about a quarter of it Okay, if you think about greenhouse gases, you think transport, power plants, you think about big things and cars, right? If you think about these warming particles, it’s actually transport and this other 25% is wood and other biofuels used in people’s homes Now I don’t wanna confuse you here because people think that bioenergy is a good idea Modern bioenergy where you take wood and you burn it in modern installations, isn’t responsible for these black particles coming out But what is responsible is poor combustion If you burn things badly, you can make black carbon So, these are a couple of big sources, and these emissions are difficult to estimate Also interesting is what happens as regions develop So what I’ve done here, is I’ve made bars that correspond to the fraction of black carbon in different regions that represent the sources Orange is transport and blue is solid fuel And in North America, we’ve got lots of diesel Why? We have a big country and we need to get things from one place to another As you go down in development, you see the contribution of solid fuel increasing and the contribution of transport decreasing And it makes sense, when you aren’t that well-developed and you don’t have a lot of money, you eat, your fuel is probably wood or crop waste, and that’s where most of your emissions come from Somewhere in the middle, you might start to develop industry At first, it’s not that clean Anybody who’s traveled in a country that has a lot of heavy industry but not a lot of air quality regulations, knows what I’m talking about And then, what happens? People get rich because of their industry, relatively rich And they start complaining, “I don’t want to live in this, clean it up.” That’s what we did in the early 1900s and in 1950 and in 1960, and then the clean air act in 1970 Our development path looks a lot like this in the US, from solid fuel to industry to transport

Yes – [Student 2] Use of power affecting North American (indistinct) I would think, Chinese building (indistinct) We see a bigger problem coming (indistinct) – [Lecturer] Okay, there’s two answers to your question One is that, we don’t have good measurements of power plants in China However, for the most part, a power plant operating well even if it doesn’t have a baghouse, puts out a lot of particular matter but very little of it is black carbon, its a lot of fly ash The other answer is that, there probably is an equivalent contribution from China, because remember these are just relative bars There’s probably as much from power, it’s just that their industry is quite polluting and they have a lot of residential solid fuel emissions, and so on a relative basis, that same amount of power looks smaller Here’s a general rule about black carbon emitters The bigger the emitter is, the more information we have about it, in this country they even have to report continuous emissions But the bigger they are, the more money they have, the more it matters that they’re efficient And so their black carbon emissions go down because they can burn better Carbon monoxide emissions go down, products of incomplete combustion, in general, go down Because efficiency is important, the more money you have, the more you’re able to clean up And these installations, the big installations, the wealthy installations, are consuming all the fuel or most of it, most of the fuel So, when we think about fuel consumption, we can point something big, tall stack, large industry, lots of information, please report to EPA every year But the small sources, the little ones that don’t have a lot of money And I wanna be really careful here that we don’t blame poor people for everything This is just a fact We don’t have information about things that have high emissions because they are associated with a lack of resources Not only do we not have information from them, but if you as a scientist say, “I like to study this poor combustion.” It’s it’s not terribly fundable So you get high emissions from small sources with little information And for products of incomplete combustion like this, you’ve got most of your emissions coming from things you don’t understand So, I happened to be lucky and people funded me to study it anyway I had to kind of call it something else, that was for chemistry But (coughs) I’ll give you a couple of examples Just a couple of examples from the things that we’ve done This is lab tests in the global emission models You wanna make a model of particles, go into the lab and burn some wood and say, “Here’s the emissions from burning one kilogram of wood.” So there’s that number, there’s somebody else’s study This is what we found when we went out, and measured in use cooking And the only way we could do it, cause it’s kind of silly to go knock on people’s doors and say, “Hi, I’m from the United States I realize you don’t really have much to eat, but can I measure your stove?” So we went out with NGOs who are working in communities and got these measurements And there’s what we found on factors of two to four higher than what was measured in the lab So I’m just gonna be showing you examples of how we don’t understand these little sources And usually what we don’t understand them, they’re higher than we thought Vehicles, it was a Bangkok, Thailand And what this is is a frequency graph Here’s opacity, which is a measure of particulate emissions, especially black emissions, it’s not perfect Frequency, 100% of the cars measured

in the lab were below opacity 60 and 80% were below opacity, say 25 When you go on the road and you get cops going out with opacity guns, how many are less than 25%? Less than 10% of the cars There’s such a huge difference between what you can measure in the lab and what is really out there And why? Because when you have a program to test cars and you say, “Please come test your car.” Who’s going to show up? The people with clean cars Wouldn’t you do the same thing? “Well, I got an old junker I don’t think I’m going in for that.” So they’re severely under sampled in testing programs And when we do future projections, let me just show you what happens This maroon color is super emitters We don’t know much about how they evolve We don’t know much about how many there are, but taking the little information we could get, we put them in a projection of future emissions And right now, 2010, it looked like about half the emissions, this is global And that is not unthinkable, because you will hear people in this country say, “10% of the vehicles, produce 50% of the emissions.” That’s pretty common But what do you project into the future, here come the emissions standards And these colors are different kinds of cars with better and better and better standards Your emissions standards can clean up the normal fleet Meanwhile, again, we don’t know much about this, but meanwhile, according to our best idea of projections, well, the normal vehicle emissions are coming down That tiny little fraction of the fleet, that smoking, is producing a greater and greater fraction of the emissions So, here’s a story that says, “Well, we’ve got these absorbing particles coming from transport, and we think we can clean it up.” Unless you remember that there are these high emitting vehicles out there, and they behave differently than everything else, and we don’t know how many there are And so, in one story, it is getting cleaner And it maybe more like the real story that’s getting worse Okay, I’m gonna skip that bit So the summary is, that there are sectors and fractions of sectors, and by sectors I mean groups like transport and household energy, that have not as much carbon dioxide So when you think about greenhouse gas policy, you ignore them, but they’ve got high particle emissions Those include household solid fuel and high emitting diesels And yeah, they have significant contributions to climate warming particles and gases, but they’re not on the climate change radar They’re not on most people’s climate change radar So small sources matter, especially when you get this kind of poor combustion producing a greater fraction of incomplete combustion So now here are more questions for you I’m gonna raise some issues How do we manage climate change now? Climate change isn’t just the long-term question anymore Not when we have Arctic melting So there’s median sea ice in the Arctic That’s what it was in 2007 It’s a pretty big change Here’s the dilemma, back to talking about sulfur Reducing sulfur emissions is for the most part, good for health and bad for climate ’cause you’re taking off the mask Some climate tipping points are pretty close Should we continue with reducing sulfur? Should we save people’s lives at the cost of melting the Arctic? That’s an extreme way of stating that What should we do there? Some people have proposed, as a partial solution, at the same time, reduce emissions of warming air pollutants like black carbon and also ozone which I haven’t really discussed here So we’ve got a group of solutions,

the usual one, greenhouse gas, is building up in the atmosphere Even if you turn it off, you have the response to today’s atmosphere at concentrations And in contrast, just for example, reduce black carbon absorbing particles They’ll go away in 2100 They’ll be gone in 2100, probably, or 2050, maybe And you’ll be stuck with a bunch of greenhouse gases But right now, if you turn them off, you turn off the warming immediately And so if we have this problem, we’re close to melting Arctic ice, maybe we wanna turn it off, black carbon emissions now There are other things that I haven’t talked about For example, when these things settle on snow, they put something black on on snow and it melts it more quickly And so, people are now concerned that black carbon is contributing to Arctic melt in addition to just Arctic or atmospheric warming So, we are stuck with this management challenge for greenhouse gases People are now talking about black carbon as a quick fix contribution to climate solutions including; Hillary Clinton and Al Gore There’s bills in Congress talking about action on black carbon So, Hilary said, “Look, we have these short-lived climate forcers black carbon, ozone, let’s deal with them This is something that’s still being floated on Capitol Hill and in places like Arctic Council.” Question to you, we have human impacts on climate now, we don’t have to wait to see them, we’re seeing them now So how do we balance that? Because we do wanna think about the long-term It was failing to think about that long-term that got us a bit into this mess, in the first place And yet there are lots of people who say carbon dioxide is the only thing We have a long-term problem, we have a short-term problem So that’s one question And then question two, is if a single action has both a beneficial result, health, for example, and a negative result, climate, for example, how do we balance those? So again, take home It’s bigger than greenhouse gases You have lots of pollutants affecting climate In some cases, especially black carbon and products of incomplete combustion, small sources matter And finally, there’s a portfolio of solutions that includes your standard climate solutions to carbon dioxide and as well includes rapid action, where, when, what can we do to change this particular location now or soon? So, questions and answers about our fire dilemma Yes – [Student 3] (indistinct) several models that you use them to predict the temperature decrease and distribution and (indistinct) then at end of your prediction, it’s like how much of the contribution of the carbon black through the global warming (indistinct) How much of it could impact the temperature increase-? – Okay, so the question is, I think about future temperature change, and you hear scary numbers, like five degrees, C temperature change, C of Fahrenheit And so, the question is in the future, how much would black carbon contribute to that temperature increase? (clears throat) The statement that you started off with is these models must be considering this And the fact is that they really aren’t for a couple of reasons First of all, the projections of how emissions will evolve are really bad So far people have just either said,

middle go up sort of linear increase over, it will come down, it’ll be all gone So there’s really not yet a good connection between social and technological behavior that drives these pollutants, and predicted increases in the future So, most of what you’re seeing, when people say, give a temperature increase for a certain increase in CO2, is they’re really just estimating a total forcing, and they’re saying, “Wherever it’s from, this is the warming increase.” They’re not always saying, it’s this much CO2 in as much sulfate and this much black carbon, in fact, they’re usually not How much of a solution could this be? I think is a relevant question If you remove all of the black carbon particles, for example, which we probably could, it would be a small fraction of a solution, but everything is a small fraction of a solution There was a paper in Nature Geoscience this year, an editorial type of paper, where a group likened it to one of the wedges used by Socolow economist who said, “You’re not going to get all of the carbon solution from one thing, you need little bits, little wedges that make up the entire solution.” And they had 15 or 16 different solutions So the group that wrote this nature paper said, “This is about the size of a wedge.” – [Student 2] You talked about the atmosphere blackened by black carbon, does that allow sufficient transport to get to the ice sheets, and if you will, because what does (indistinct) is the fact that once the target that’s on the surface And it has a lifetime of hundreds of years of continued impact there I don’t know (indistinct) about global transport towards your seven-day transport to get to the green (indistinct) sheets And what if you did take the content that is on the surface? – Okay, so I think there are two questions there First of all, is the atmospheric lifetime of black carbon long enough for it to get to the Arctic? Yes, no question You can see it in the Arctic You can measure it in the snow People are measuring in snow It’s not all of it getting there, but yeah, some of it is getting there And then the second question is, once the material settles on the ice and affects the reflectivity of the ice, that’s a very strong effect, and it could sit there for a very long time And the answer there is, it really depends on the snow and the ice dynamics So if it’s in a, if it’s depositing in the first place, then there’s snow If there’s snow, then it gets snowed over the next year or it could be carried away in runoff And some of those interactions between the particles and the meltwater are not really well understood So you could actually have a large lifetime or you could just have it be carried away And I think that’s one of the big uncertainties in determining the impact – [Student 4] I also have a two-part question Is there a relationship linear or non linear between CO2 emissions carbon black emission? And second question is that Your picture shows that the carbon black is coming from combustion and solid (indistinct) Did you know that (indistinct), that combustion is a very complicated science, where there might be hundreds free radical reactions in it? So, I think, when you have 99.99% efficiency, you still are going to have tons of carbon black emissions into the atmosphere, especially in China So, how can we avoid that if we’re still going to burn (indistinct)? As I said, combustion is never a hundred percent efficient – Okay, so the first question was, is there a linear or non-linear relationship between CO2 emissions and black carbon emissions And then the second question was, well, combustion is so complex that even if you have mostly complete combustion, you could still have black carbon emissions I think you answered your first question with your second Yes, yes Because combustion is so complex, that there isn’t a very good relationship between CO2 and black carbon It’s easier just to measure from different kinds of combustion

and say, “Okay, that’s what it is for that kind.” If you look at the combustion literature and how people try to predict soot formation in very simple flames, it’s still very difficult And so, very complex nature of a real flame where you have all kinds of turbulence and different temperature pathways, it’s just too hard To answer your second question, I think what you’re saying is even if most of the carbon goes to CO2, you could still have some black carbon And the answer is yes, especially solid fuels You’re always gonna form something at the flame front, and that’s what you see glowing Most of the glow is little particles radiating But those can be burned out So they have fairly well understood oxidation kinetics And if you keep it hot enough for long enough, the soot or black carbon that is formed, will be burned up And that’s usually how it’s done You don’t try never to make any, you just make sure that you burn it before it exits Hancy – [Hancy] I have a two part questions – Everybody’s got two questions, is this is a pattern here? (indistinct) Yes, okay So, first question is, is there a black carbon from volcanic eruptions, and the second question is about forest fires As far as I know, there’s very little black carbon from volcanic eruptions, there’s a whole lot of sulfate And you can see the volcanic signal in the temperature record because there’ll be a dip in temperatures for a year or two following a volcanic eruption So that says that volcanoes are producing mostly cooling aerosol, if not all Forest fires Oh, dear There are questions about whether that is controllable and manageable Certainly, most of it, certainly, a lot of it isn’t, especially in very remote locations like Siberia There’s also a lot of question about how much of it is human generated So, some of it is forest management that needs to happen Some of it is land clearing Some of it is due to people being there including a lot of the ones in Siberia, apparently And so, I don’t have a good answer for your question When I think about reducing black carbon emissions, the first thing I do is remove everything that burn forest fires and then worry about that later So, you may be right There may be some that you can touch Yes – [Student 5] (indistinct) interested in the natural cause of the black carbon, in the historic record you see, I mean, caveman here, but do you see periods where Prairie would be burned or manmade fires or even natural fires maybe don’t occur as often now? I was curious if that shows up in the sort of hidden in the modern historic record – Yeah Yes And so, we’re just now getting historic records like sediment records with very good time resolution It used to be that they were like every 10 years, but now there’s ice cores that can do seasonal variations And so you can see forest fires in that What I haven’t seen, because I haven’t looked, is how those burning cycles vary And yeah, that’s something that is really interesting but I just don’t, I don’t know how well that’s been characterized There certainly are people who have looked at not black carbon as an indicator of historic open burning, but the leftover charcoal So you can see in sediment records where there’s more charcoal, that was of higher burning period – [Student 5] But it had to be locked up (indistinct) – Yeah, North America would be interesting, but I don’t think there’s been fire suppression everywhere

So it would be interesting to contrast those But again, the place you have to look is in the almost paleoclimate records, the ones that have sort of year or 500 year histories So that’s a topic I don’t know very much about (indistinct) I’m totally curious about them the Prairies here (laughs) Yes, we have – [Woman] We will take no more questions- – We can, we can take only these two – [Student 6] I had a comment and a question – Okay – [Student 6] A comment is that, is I think the short-term solution is very important because it lowers, it has a cooling effect And I went to seminar (indistinct) too long ago, and it was about (indistinct) One degree increase in the surface water temperature in the ocean, will be increased 60 inches of rain That’s why there is so much rain, and this typhoon and So, I think this short-term solution is very important And also my question is that, black carbon contain PAH, how come the lifetime is only and days and weeks? I mean, there’s PAH in them – Okay So, the You’re thinking of the long lifetime of PAH in the environment, right? When I’m talking about days and weeks, I’m talking about in the atmosphere So the PAH is aren’t orbiting the in the atmosphere, they’ll be deposited and then maybe re-emitted But the atmospheric cycle is emission and then wash out of some kind or dry deposition And so the lifetime of black carbon in the environment is actually thousands of years (indistinct) – [Student 7] I remember that there were engineers, they proposed putting sulfate aerosol particles in the stratosphere So, (indistinct)? – You’re asking what I think about putting sulfate particles in the stratosphere? It makes me nervous I think we have done a lot of things with unintended consequences And I don’t think we need to add more of them until we understand the system a little better, if at all So, I’m not convinced that that is our first line of defense There are people who argue that we should understand it just in case we really, really find out that we need to use it I guess, go ahead and understand it But I would put it far down the list of solutions I don’t think we need to increase our footprint – [Student 5] Where we are right now (indistinct) – Well, that’s the troposphere So they’re talking about putting into the stratosphere, so it has a really long lifetime (laughing) (indistinct) The chemistry is different, and I’m not sure what the result of that would be – [Student 5] So we know that we’re not having too much of something, but there are consequences- – We do, we do indeed – ‘Cause they kill up porosity in earth thus bring about- – I feel like we, yeah, we’re still struggling to understand the chemistry of the troposphere and the stratosphere Some of it’s well understood ans some of it isn’t So I just don’t feel like we’re ready for a solution like that – [Student 5] And it doesn’t rain (indistinct) – It doesn’t rain, but there is chemistry, some very important chemistry, like ozone Thank you