welcome to the science for the public lecture series the science for the public is an organization committed to bringing science information and issues to the general public this is our website for our program log i want to thank the friends of the belmont public library they sponsor events like this and i want to especially thank of on staff the director of science for the public she coordinated this event that you guys are getting to enjoy today i'm going to let her come up and introduce danielle but let's give a round good evening on the step for science for the public and i welcome you to tonight's special lecture clouds chemistry and climate change why our current climate is what it is our speaker is dan sits so professor at the sphere chemistry at m i t dr said so is an expert on the relationship between clouds and climate so it is our very great fortune well time to this week to have him after following the two massive hurricane erma although clouds and the particles that produce them are core features of climate and climate change we don't really hear about this process so after tonight we'll all have a much better understanding of how climate scientists analyze this complex relationship between atmosphere and ocean and these particles in the atmosphere that all affect the climate doctors so is an expert on the atmospheric particles that produce the clouds and how clouds regulate earth's temperature tonight he's going to explain to us what this work reveals about earth present and future climate he'll discuss also why the excess c o two in the atmosphere will continue to remain a problem and he's promised to also mention something you may not have heard about called geo engineering quite a traversal thing and he's going to give you the facts tonight about this doctor so has been involved in major atmospheric missions for nasa and maybe he'll tell us a bit about that too and he's received numerous awards he is one of my favorite translators of technical information for experts like the rest of us and we are very honored to public it's been a great opportunity for me in particular but i think for our community in general which is this idea that we put a lot of money into science technology engineering math education for kids that are in grade school but we sort of forget about people after they get to high school and i think that the work she's been doing is absolutely critical which is that you know as we all get older we still want to learn things we want to find out new things we want to get information and how do we do that and i think science for the public's absolutely critical and so ivana to give you the title of  what i'm going to be talking about today she asked me to add a little bit to what i normally talk about so we're going to talk a little bit about c o two carbon dioxide and its fate in the atmosphere and then she asked me to say a few things about geoengineering which is a topic  that is very controversial right now i am not a proponent of it i'll try to lay it out for you and allow you guys to make an informed decision about it what i will say is that this is a great audience and it's a pleasure to be here so don't wait until the end for questions if you raise a hand i will definitely break if something's not clear you guys want to talk about something i think we should go into that in more depth so don't feel bad about that i always tell my class the worst thing you can do is hold their questions still and then forget what they were or not go down a path that you know we all want to go down so with that launch right into it with one of my favorite quotes and i think it's a great way to get talking about climate because what we're going to do first is talk a little bit about climate and then we'll get into our special area which is particles in the atmosphere and the clouds that they spawn so this is george santayana quote those who cannot remember the past are condemned to repeat it and so what does that mean for climate it means that we really have to think about the climate of this planet not just today yesterday last week but but really over thousands of years i think that we're often made to think that the climate of the planet is somehow very stable and that is absolutely contrary to the evidence that we have so this is a time series and on the bottom axis it's going back almost a million years eight hundred thousand years in time and this says what the temperature of the planet is and that's on the y axis here and there's this number over here which is zero which just means it's the same as some arbitrary number and you can pick what that number out is it could be what it was today it could be last year could be ten years from now if you could be anything that you wanted to be scientists normally get together and we pick out this mysterious this mystical year seven hundred fifty the reason we do that is that people normally agree that that's before the industrial revolution it's before humans really had an impact on the world around them and so that zero that we pick out is some climate that was around this planet about two hundred fifty some odd years ago and what you can see is if you go back in time climate swinging back and forth it's a little bit warmer at times than it was city at other times it's much much colder so this isn't degrees celsius which is a little bit over degree fahrenheit the degrees that we commonly use in the u scientists we tend to use degrees c but you can see that it can be as much as eight degrees cooler and so this is no surprise most people have heard about these periods in earth's climate these are ice ages and we came out of our last one something over ten fifteen thousand years ago and and so that would be the last blue arrow on there there's also so called interstitial periods these mean periods between ice ages when it's somewhat warmer so what causes this this is natural climate change this is not something that humans had an impact on humans anatomically modern humans were around for a lot of this record but of course who were at the beginning of it we really didn't have an impact on the planet and so this is not new science this was actually worked out in the one nine hundred twenty s a very smart scientist figure this out and when he realized was that these climate cycles the warm periods of the cold periods correlated with orbital mechanics they can the correlated with how our planet moves around the sun and so what's often thought of is that the earth is something like a top and you can think of if you spin a top it's spinning around but it's not stable it starts moving like this it might move around like that and so all of these orbital parameters change over thousands and thousands of years just like that top is spinning around or it's precessing around and blog of each worked all of this out and people have been doing this better over time and trying to figure it out but he sort of picked out that there were three or four really important features in the earth's orbit around the sun that contributed to the climate of the planet it being a little further away a little bit closer that we were spinning so that summer time was during the months of july in the northern hemisphere that winter time was sort of around december in the northern hemisphere in the opposite in the southern hemisphere and so he he worked all of this out and so this is by the way i leave this at the bottom but but the source of where this all comes from is always recorded bottom just so that you know what i'm talking about so this is  from universe today and what they did was they have shown very nicely here that that tilt is here the eccentricity of the orbit is here this is that perception that top like behavior all of the different factors and if you add those together you come up with this number that's called daily insulation that's a fancy term for saying it's sort of like the amount of sunlight that's reaching the earth because of all of those features and then at the bottom you see these two records and so these are temperature proxies i'll talk more about these  just a minute but this is a way of seeing what the temperature of the planet is and so what the long of it was able to do was look backwards in time and realize that these different parameters when you added them up lead to what the temperature of the planet was and so this is why the temperature of our planet changes over a long period of time so that's over thousands of years but if you look at shorter time periods earth isn't really changing its orbit around the sun those things aren't really changing over time and instead there's different things that are forcing the climate system so for us to understand this what we can do is acknowledge that there's these ice ages and these interstitial periods but we really want to zoom in on what's going on right now or maybe over the last few thousand years while we've had a human civilization going on so we can do that we can sort of zoom in on that part of the climate record and so now on the x axis this is year this is not hundreds of thousands of years anymore this is a couple of thousand years you can sort of think of this going back to you know the roman empire or something like that and now we have global temperature on the other axis there and the first thing that i'd like you to notice is that even while we have these huge climate swings over hundreds of thousands of years this temperature is very stable it's saying that the average global temperature and this is the idea that you take the temperature everywhere on the surface of the planet of over the course of a year you add it up and you average it that global temperature has change really by no more than about a half a degree celsius something just under one degree fahrenheit over those thousands of years there's a couple different colors here and so we should sort of talk about these a little bit more and think about what they mean so first off you'll notice that before this year eight hundred eighty and this is another magical year for scientists that i'll talk about in just a moment before that the temperature record is in the sort of yellow gold color on here and for the folks in the front row you can see that that's surrounded by this sort of shaded region the reason that it's that color is that we as scientists acknowledge that we didn't really have very many accurate thermometers before about eight hundred eighty s so if we want to understand the temperature of the planet we have to use things that are called proxies we have to look at things like and see how wide they are how fast trees are going how good the climate was for them to grow we can do things like look at air bubbles past climates past air that's trapped in ice in glaciers and that type of thing we can also look at the record that since the lack tights in caves and things like that and so this can all be worked out to figure out what the temperature is that's not as good as a thermometer and that's the reason for this shaded region here which acknowledges that we're not very certain about it we think that it was this temperature but it could have been somewhat higher and it could have been somewhat lower and so word knowledge in that now in eight hundred eighty this magic year that's when we not only had three monitors we had had them for some years number of years before but now we've had enough of them around planet that we can start thinking about a global temperature and making that record that sounds like it's fairly recent but believe it or not blue hills which is just south of us was actually the first temperature record in the united states and it started in eight hundred eighty four and so that's why this year is there even in the u s we didn't have a temperature record going on a climate record going on before the mid eighteen hundred eight hundred eighty s and so what you'll see is that that temperature is very very constant over this period of time there's a few weird features that are going on in here so there's these periods that look like they're a little bit colder there's a so called little ice age there are some volcanic eruptions and we'll talk more about those later they put a lot of particles into the atmosphere that scattered sunlight away and it got colder there's another period that's often called the medieval warm period and what you'll notice is that even though it's called the medieval warm period and everybody talks about how wonderful it is it's actually cooler than it is now today but what is very striking is this increase some time after that temperature record started really within the last few decades where temperatures started taking off very quickly and so what i'll remind you is although we know that there's a natural climate forcings due to orbital mechanics this is not orbital mechanics it cannot happen that fast this is a rapid change in time that has a fingerprint of of a couple decades so it's not what we talked about that malaki of it figured out it's got to be something different one less thing that i'll make a point about is that this you can think of his being sort of the record of human civilization there were cities there was agriculture that went back some thousands of years before that the same type of climate record the same stability was there and so those wild swings in temperature that you saw earlier there were atomically modern humans for a large part of that but they didn't make a civilization and there's been a lot of scientists that have looked at this and talked about that civilization and stable climate is not an accident that there's a lot of evidence that having a stable climate allows you to build cities make agriculture populate regions and you'll see that again we've had this very stable climate and so i just want to hammer home the point that this is really important for civilization is having that stable climate we're starting to now get outside of a region that we know anything about we don't know how civilization responds to warmer temperatures than this or much colder temperatures to be quite honest with you so i mentioned that this can't be forcing that's due to orbital mechanics that there has to be something else going on and we have a hint of what this is and that's carbon dioxide so if we go back in time we can see that as climate changes there's also changes of things other than just mechanics we also have carbon dioxide changing in the atmosphere and i'll talk about this being natural then we'll talk about the effect that humans can have on this in in a few moments but we can see on this plot is that temperature  is on here in blue on the upper panel and the amount of c o two in the atmosphere is on here in the lower panel in the red color here and you consider see these swings his temperature goes up c o two is up when temperatures down c o two is down and so this is sort of giving us a hint that maybe there's something else to look at here for us to understand what could force climate over a few decades and not over a few millennia so if you watch the nightly news you watch a bit on you tube or you read the paper what you think is that you know we're just starting to figure out climate one of the things that i want to get across you guys tonight is that it's absolutely not true we as humans have been concerned about climate and trying to understand the earth and the earth system for hundreds of years now and so this is a sort of a person here among this is john tyndall he was a brit he was working in sort of the mid eighteen hundreds the reason i like him is that i'm an experimentalist i go out and do field work i build instruments in the laboratory and that's what tindall did as well so this is an instrument that he had called comparative spectrometer the idea here was that he was able to put different materials in this tube like structure and then he could put different types of energy through it you can think of that as being sunlight or heat and he'd see what was in the tube and how it reacts with the heat or the light that was being put through it and then he would report back on this and so tender was really interested in the atmosphere and the effect that it could have on things like sunlight coming down as well as the heat of the planet is as the planet was trying to sort of really what it was trying to radiate that heat out into space and so at first when he decided to do was put you know the major components of the atmosphere into his spectrometer he put oxygen in there he put nitrogen in there and lo and behold he figured out it did nothing scattered a little bit of sunlight when he put light through it it did do anything to heat from the earth or anything like that it was until he started putting some strange stuff some very low concentration materials carbon dioxide and ozone into it that he started to get a result didn't do much to sunlight but what he realized was that heat that the planet was trying to give off got sort of trapped by the material in the spectrometer and reradiated so if you tried to put heat through it it didn't just pass through that material would absorb that heat and then reradiate it in a spectrometer would warm up and so he's got this famous quote where he talks about how the earth would be in an icy grip if it wasn't for these low concentrations species like carbon dioxide an ozone being in our atmosphere and so he's worked out the first part of climate change the first part of human induced climate change that is when you realize that there's these materials in the atmosphere that are really important for maintaining the temperature of our planet i need to give a quick shout out to eunice foot on the first line here so eunice foote was a scientist a contemporary of tindall's she was working in cambridge our cambridge in cambridge massachusetts at almost the same time in the mid eighty's hundreds it turns out  that at that point in time we were perhaps not quite as evolved as we are now we did not allow women to present its scientific conferences so that's something that's changed in the last hundred fifty hundred seventy years much for the better eunice was a fantastic scientists she work lot of this at the same time or figured a lot of this out she then had to pick a man to go give presentations at scientific conferences for her if she had any shortcoming it was perhaps in picking the person to present her material it turns out that she didn't do a very good job of that and whoever was presenting that material was not very engaging in a lot of it was lost as it went through as we went through the years and so tyndall got a lot of the glory for this and eunice lost out on this there was a really nice article in the new york times about her i think it was a little bit over a year ago one of my colleagues brought it to my attention and i think she's got a nice write up in the globe in a few places like that so it's a fascinating story and it's somebody i think if you pay attention to climate that you'll start hearing more about over the next few years ok so we're still talking about natural climate and what's happening in the earth system and so tyndall again is working out most of how this happens and this is been you know over the subsequent decades sort of figured out and so you can think of c o two of stabilizing element of our climate system c o two is being put out by by various activities you know you can think of a natural one being volcanoes erupting in putting c o two into the atmosphere so that's helping to keep the planet warm by keeping some of our heat in acting like a blanket over the surface but if those volcanoes just kept erupting that would mean more and more c o two in the planet would keep warming up and we obviously know that's not happening so there's something that's stabilizing it and so qu naturally one of the things that we realise is that c o two makes its way into the ocean it combines often with other materials things like rocks that are being weathered and you end up getting this material calcium carbonate and the sediments out finds its way down in the sediment and then it's trapped and so this is a perfectly natural cycle and it keeps c o two in a relatively even keel in the atmosphere you can think about the ice ages we talked about earlier in the playing ice ages less plants so c o two is going to go up plants are not using c o two what's going to happen you sort of kick in this sediment thing c o two goes up it helps get the temperature of the the planet up it helps get you out of an ice age at that point the plants are taking up more c o two so this is a nice sort of happy balance you can think of the earth sort of going back and forth through these different climate periods over time but sort of self regulating and self stabilizing but again the key again here is this is over thousands or even millions of years these are not things that are happening over a few tens of years and so this is just sort of graphically saying what i just said you can think of these volcanoes putting out c o two atmospher up the planet temporarily warms you have a bit of weathering you make more of this calcium carbonate that gets trapped c o two goes back down the temperature of the planet returns everybody's happy you get sort of these long time swings that's all well and good planet was going on for millions billions of years in a perfectly happy fashion somewhat warmer somewhat colder and so on and then humans came along so what effect are we having well this is just sort of an accounting of what's been going on i kind of like it because it's one nine hundred seventy which was the year i was born so it sort of tells you what's been going on since since that time and so what you can see here is this is c o two from fossil fuel combustion as well as from other sources but from human activities and you can see that over the years there's c o two that's being emitted by those activities this is not natural this is what we as scientists call anthropogenic or or human induced and so this is putting material into the atmosphere that we know has an effect on the climate of the planet and not only are we putting material in but every year that ticked by has been a little bit more of that material so it's not it's putting that material but every year a little bit more a little bit more a little bit more and you can see that that's constantly keep it's constantly gone up and so that's the amount that we know is being put there we can sort of do an accounting again of you know the number of power plants the number of cars and so on we can also measure what's in the atmosphere so we can go out and we can stick measurement  devices on the top of the roof and we can look and see how much c o two is there and so that's what's being done here on the the y axis on the left axis this is the amount of c o two this is p p m that's since for parts per million so you can think of a million molecules in the atmosphere if you did that there would be in the year one nine hundred seventy again so this this year the last one started out that it would be about three hundred twenty of those molecules would be c o two we can fast forward to two thousand and ten and it's something over three ninety if anybody is reading the news about a year and a half ago we had four hundred and so nobody in this room will live in a world that has less than four hundred parts per million c o two in the atmosphere again that's sort of in the rearview mirror we're going to keep going up and so these two are directly related we're putting c o two into the atmosphere we're putting more every year and we can see the amount of c o two in the atmosphere rising as a response to that this is just a quick quote from the  intergovernmental panel on climate change report and they just say that you know within that last eight hundred thousand years where we have this sort of nice proxy record c o two is higher than at any time in the past it's about forty percent higher than this this mythical year of seven hundred fifty before human activities before the industrial revolution took over and so we have to sort of update that slide that i showed you earlier with this sort of nice cycle this nice balance going on of c o two being put out and then slowly being taken out of the system by by rocks weathering by deposition and so now we have factories in here which is sort of just meaning you know human activities and so what are these doing they're producing that c o two they're putting it into the atmosphere the atmospheric amount of c o two is rising a consequence of that is that there's more c o two going into the oceans and people here probably heard about ocean acidification that c o two going into the oceans and you also have an increase in photosynthesis there's evidence that we have more plants now more material in  bio system as they respond to the food that they have the c o two that's in the atmosphere so all of these things are increasing because of this human edition of c o two and this is sort of knocking the system a little bit out of whack ok so who is it that first sort of considered the concept of humans putting c o two in the atmosphere to do was just working out how did the climate system work spawn arrhenius in the late eight hundred early one nine hundred was a figured out how humans could affect this so this is his famous quote and basically he's saying here if you increase the amount of c o two in the atmosphere that we can expect that there's going to be a rise in temperature you put something in there that helps trap heat something like a blanket what's going to happen your temperature is going to go up as a result so i was the first one that worked out something that we as scientists call climate sensitivity and it's this idea that if you take an amount of c o two and you double it so pre industrial you that was about three hundred parts  million if you double it to six hundred parts per million what kind of a temperature increase would you get so he worked out the math on this and he said it was about five and a half degrees c this is something i tell my students never to do he wrote a paper and said it was about five and a half degrees c then he realized he had made a math mistake so what do you do wrote another paper so he made a mistake but he got two papers out of it that's not a good role model for students nowadays i tell them not to try that but he did revise it and he revised it correctly for the math that he was doing down to about four degrees c so again you know about a degree degree and a half fahrenheit so about six degrees fahrenheit this was the first estimate that we had of climate sensitivity so again humans put the c two in we double it what's the temperature rise so very often you'll notice at this point that i'm a bit of a science history buff people say oh this guy when he was really thinking ahead the industrial revolution had just barely kicked off and he's worried about climate change absolutely not true he was reading a paper and this came out in one thousand eight was a scandinavian he was from sweden and so he was interested in burning coal intentionally to increase c o two because he thought scandinavia was too cold he actually writes about how he's tired of the cold winters in scandinavia and so what he's going to do is he's going to light the coal fields of northern europe on fire increase the temperature make it nicer in scandinavia he thought then the agriculture region would move north you know it would sort of move out of germany and scandinavia he didn't seem to write very much about what would happen in places like southern europe and africa he was very sort of you know scandinavia centric at this point in time but that's how we all got started in this climate world so one of the things that yvonne asked me to talk to you guys about today was what's the ultimate fate of the c o two and we've already mentioned this but it should be pretty obvious by now if you put that c o two in the way that earth the way that our earth system tackles it is to draw that down and so there's weathering of rocks production of this calcium carbonate sedimentation and sequester seaquest ration of that material but it's not fast it takes thousands of years  use that quote from the paper that i showed you earlier of you know it's on the time scale of order of a million years so if we put c o two into the atmosphere if we drive here if we go burn something at home that c o two those c o two molecules are going to cycle through our  some of them are going to stay in the atmosphere some are going to make it into the ocean but eventually they'll be removed from the earth's system but it's not going to take place quickly and so this is just a quick plot and there's three different things that are being shown here important one is the concentration line which is this black line right here and so this is the amount of c o two and you can see it rising to the year two thousand and fifty this is a projection this is sort of saying that we as humans sort of get our act together in the next few decades and we realize that material and that's the solid line resulting in a temperature which is the red line and so those things lag they take time to go away and you can see this is going out several hundred years so this is the are twenty two hundred i'm pretty sure that nobody in this room is going to be around to worry about this but c o two that we have emitted now up to the year about twenty fifty which is going to be due to us would still be causing the facts temperature rise in the year two thousand two hundred in fact this will continue on for about one thousand years so just remember that when you drive home tonight that those c o two molecules are going to be you know messing around with the atmosphere and changing things changing the temperature for hundreds even a thousand years so it's not a problem that if you shut off the taps or you shut off the cars tomorrow that it just goes away this is a much longer term issue so let's go back to spot and sort of ask ourselves well how is he doing so again let's just sort of recap what we did in the first half of this talk we've figured out as scientists that c o two can have this effect on the temperature of the planet we put more of that material into the atmosphere and we can see the temperature go up since the year eight hundred eighty when this rise already starting but it really sort of accelerating we've had modern temperature records and so this is a plot a few decades later in the year one thousand nine hundred and the difference between that in a few years ago two thousand and twelve and this is saying if i had a temperature in the thousand nine hundred in a year a temperature in the year two thousand and twelve and i was able to do that over the surface of the planet how different would they be on average and you can see that this is the temperature this is zero and these warm colors here means that the temperature in that location is warmer there's some places that we don't have very good coverage there's some places that have gotten a little bit cooler but by and large most of the planet has seen a warming and that warming has been just under a degree c something just over a degree fahrenheit and so we know that that's happened because of the records these are direct records that we have in fact if we sort of think about what the warmest years in history are again going back to eight hundred eighty when we've got these modern thermometers the warmest years on record look like this so anything strike you about those years they're all recent right they're all within my lifetime certainly i think they're within the lifetime of the folks that are largely within the lifetime of the folks that are are with in this room when i first started doing this about ten years ago there are a few on here from the one nine hundred thirty s and for those that read history that was the great depression that was the dust bowl era which we sort of think about as being this remarkably warm period in our history in the history of our country those have all sort of like a pez dispenser got knocked off as you you pop the warmer years on to the top so last year was the warmest year on record the year before was the warmest year on record until last year and so on there's a little variability in the system but you can see the two thousands are largely in this sort of top twenty you know the hits per year that we have on here there's a few years from the ninety's the ninety's are going to start getting knocked off for the twenty teens the twenty twenty's are going to come in and so on and so this really does make sense i mean this is all in keeping with what we understand is as scientists that's been worked out since the time of tyndall one of the questions though is is our friends fun doing number he estimated that if you double the amount of c o two you get this four degrees centigrade change in temperature but what i'm saying here is that carbon x it's gone up by about fifty percent that should be about two degrees and yet it's somewhat less than that it's about a degree so it's fonts off he sort of missed something if he was right to be correct c o two has gone up forty three percent with his math we multiply that should be about a degree point seven and it's only about half of that so the question is what did he miss why isn't it warmer now than it even is already warmer but why is an even warmer more than that and so i'm just going to recap the first half greenhouse gases mainly c o two but there's a few other greenhouse gases are trapping heat that would otherwise escape to space that's a good thing the temperature of the planet would be below zero degrees c below thirty two degrees fahrenheit if we didn't have any c o two so be happy there's some c o two there but we as humans are putting c o two into the atmosphere and that's got to cause a change in the temperature of the planet so however warm it was that we were happy with it's going to be a little bit warmer because of that c o two so what did miss well this is your hint so i'm going to ask you what this picture is missing and this is actually a picture this is from the japanese space agency so what you can see is that they took this nice image of the earth it's actually a mosaic they'd a satellite in orbit and they were able to take pictures and they sort of stitched them together to make this beautiful image and they intentionally took pictures at times that didn't have clouds there's no clouds there and so if you look at an image of the entire planet in any one time and this is from nasa this is from apollo it should look like that and it's not just clouds if you look very closely there's also things like mineral dust storms that you can see there's smoke plumes and things like that that are here that weren't in the japanese space agency picture i love this image i had this is a kid on my wall but this is the correct one so this is the heart of the research that we do is understanding the effect that these clouds and the particles that are in the atmosphere have on the climate of the planet and so i'm not sure how obvious this is as john mentioned when she was doing the introduction i think that most of the folks in this room have heard about carbon dioxide and global warming but it's a little bit more rare that you have heard about things like particle effects and cloud effects on climate and so i love this image this is something that i think really speaks to why particles have an effect on the temperature of the planet so this is singapore mit the school that i met has a joint institute there and one of my good colleagues actually spends about six months out of the year there and so he was there in two thousand and thirteen he sent me a few pictures they didn't turn out real well so i had to grab this one from the b b c but this is singapore with smoke over the city and so what you can see is that this is otherwise a bright clear blue day just like we had in boston today and instead of seeing that blue clear sky in the background the sun lights coming in it's striking that smoke plume and some of the radiation is being reflected back into space the reason that it looks sort of blurry or diffuse is that some of that energy some of those late photons are making it to the camera and instead of making it to the surface of the planet so to see this again it's a break clear blue day that sunlight should all be reaching the surface of the planet and warming it up but it's not because it's hitting the particles and it's scattering all over the place and some of that is hitting the camera some of it's going right back out into space and it's not able to warm the planet so at this point you might ask a question and say well smoke is natural there's wildfires you know this isn't human activities this is completely natural that's not true we actually know where the smoke came from they were clearing land they were clearing peat bogs around singapore at this time so that they could use that land for cropland agriculture that type of thing so these were wildfires that were set by humans where natural material was being burned to change land usage so these are human caused particles just like the things that come out of smokestacks out of cars out of that type of thing this is just a stiffer in source of human made particles biomass burning land usage changes that smoke moves over the city and as a result the temperature of the city in this case but really the temperature of the globe because of all these particles goes down so as scientists we call this the direct effect the direct effect of a particle interfering with sunlight and making the temperature of the planet cooler so it turns out that particles are not only important directly but they're also important in directly and what i mean by that is that at the heart of every droplet in every cloud or every ice crystal in every cold cloud is a particle that nucleated that form that droplet that water had to condense somewhere it just doesn't condense out of the atmosphere it condenses on a particle so if we agree that there's more particles now because of human activities that means that there's more cloud droplets there's more ice crystals as a result there's more clouds and as you saw in that image from nasa before those clouds are white they're bright and so they're reflecting sunlight so if you have more clouds more coverage of clouds you're going to end up with more scattering you're going to end up with a lower temperature of the planet ok i don't expect you to believe me i'm hoping that you'll believe this guy here that's a joke to me in my lab and so this is some work that we do with yvonne in science for the public public a while ago and so this jar has no particles in it i've put some water let me take one second just so that i don't get too far ahead of this jar it looks like one of those beer growlers that you might bring home from a brewery or something like that it actually does work that way that's what they were made for but we use them for something different this is going to be a cloud chamber for experiment so what i've done is i've put some water into that jar to make clouds the feedstock for clouds and clouds normally form if you see sunlight come down to the surface it heats up the earth the you get convection and so you get clouds sort of building up and you can see this on most summer days today was right in blue but we should have some clouds on friday and you'll be able to see this happen so i can't sort of lift this up fast enough to simulate convection and that type of activity so i have this nice little beer g hooked up to a pump to drop the temperature and so at this point in time what i'm doing is putting my finger over the inlet to there the pumps active and so this is dropping in pressure do you see a cloud in  the cloud right so i don't know what i'm talking about you should probably go home right now that's not true that is a filter so what i've intentionally done to play a trick is i'm letting the temperature of that drop the pressure of that drop there's plenty of relative humidity in there but there's no particles there's no seeds for clouds to grow on so this is trying to prove that you actually do need these particles to make clouds so let's forward fast forward just a little bit  and so in this case i'm going to put some particles in so we talked about singapore we talked about these wildfires and so what i'm going to do is i'm in a light this match here and let the sulfur burn off of it and i'm going to just try to make these bio mass burning particles these wildfire particles with the little stick of the match there in the so this is a real wood match so it's burning all the sulfur is gone there's just smoke you can see the smoke there's just a little bit of it now i put my finger of it so this is full of particles now all of a sudden can you see the cloud form there's the cloud nothing's changed except we went from no particles to particles and so hopefully this is proof for you to see the particles really are important now what i'm doing is i'm going through this is i'm taking my finger off and letting fresh air in the cloud dissipates and then i put my finger back on what you'll notice is even though looks like everything's been pumped out of there's still another cloud forming every time that i do that the clouds changing its optical properties becoming a little bit more gray a little bit less reflective but nonetheless even just a few particles in there are able to make that cloud actually i'm a screwed up this experiment one time because i was doing it and i wasn't very careful about putting this filter on there and i let a few particles in there so i could see that i was making a really thin cloud in there but luckily everybody in the audience can see that so if you have insomnia you'll have this link it'll be on the presentation you can go home and watch this to your heart's content so this is a graph from that i p c c report that intergovernmental panel on climate change report it's horrendous the complicated so just give me a few seconds to explain it what the scientists that wrote this did was they do this line right down the middle from top to bottom on here and they said we're going to draw columns on this for all the things that we think humans are doing to the atmosphere that could change the temperature of the planet if that thing is going to have a positive effect if it's going to warm the climate we're going to make it go to the right and the more warming it's going to have the bigger we're going to make that bar and so not surprisingly when you think of  it falls to the right it warms the climate and it's a big it's a lot of forcing it's the number one greenhouse gas that we have in the atmosphere as we mentioned earlier there's other greenhouse gases that are in the atmosphere they're all warming just not as much as c o two is what's interesting is when we get to particles and clouds so if we say that we had particles to the atmosphere and those particles have spawned more clouds now this falls to the other side so these are different kinds of particles and they all have to be added up and when you add them all up you get a negative feedback you get a cooling of the planet just like that smoke cloud over singapore if you think about the clouds that are being formed that's also negative not only that but there's one of the thing especially for anybody that's taking science right now or is going to take science that's going on here that you should pay attention to which is the uncertainty that error bars so for the students in the room because they're all going to have to talk about error bars at some point in a science class you'll notice that this is largely positive but we also are pretty sure about it it's no less than this and it's no more than that when it comes to the particles look at the error bar here it's huge it's absolutely amazing so our understanding of particles in clouds is much much worse than our understanding of greenhouse gases and this kind of makes sense right we've had people like tyndall and arrhenius working on c o two and the other greenhouse gases since the hundreds but really only in the last fifty years or so we started thinking about particles and cloud effects and so we're not quite caught up to them i call this one of the thing which is job security because this is what i work on and most of my work is trying to squeeze these down so that we understand them better when you add all of these things up you can think about the year that this report came out this is two thousand and twelve and you can see this large positive forcing error bar here the uncertainty is really due to not understanding the particles and the clouds but it's large you can also go back in time and sort of do the same accounting in years like one nine hundred eighty in one nine hundred fifty and you can see that there was a lot less c o two in the atmosphere so there was still a lot of warming but there wasn't as much and so that's smaller and the error bars are also smaller as a result for those that are old enough to remember there were also a lot more particles in the atmosphere as you go back in time we've actually been pretty good about cleaning up particles and so there was actually more of a negative effect in years like one nine hundred eighty and one nine hundred fifty relative to the amount of warming that we had so that was part of the equation ok so let's sort of finish up part number two again just to recap particles and clouds scatter more of this sunlight than they absorb or they trap heat and the net effect of this is that we have a cooling we offset some of global some of the global warming it's not enough to get rid of the global warming or to have a cooling effect it's just enough to cancel out some of it sort of like going to the beach and somebody throws a bunch of blankets on you but then they put a little sun shade over your head sun shade helps but you're still really hot from all the blankets that have been thrown up not only that but this is really our area of uncertainty this is why we don't understand climate change so we can add all of these things up and we can have this observed warming and what we can say is that that's really adding things together it's the large greenhouse gas we're warming other anthropogenic forcings these are the clouds and the particles we add these two things up this is the combined forcing and that's pretty close to the observed warming so in other words we as scientists can sort of do the independent accounting of this and it matches up pretty well with what we're seeing in the earth's system we're not missing anything large we're not completely certain about the effect but we're not missing anything so so we're going to change gears a little bit here but i'm going to ask you to explain why i'm doing it at this point we're going to talk about what's called geo engineering so who in the room has heard of geo engineering just by chance while educate a crowd so about half of us that's great engineering is the concept that there is something that we as humans might be able to do to the climate system of the planet to change the temperature and somehow bring it back to this normal number whatever that number is member we have the zero degrees c the average number in some year so if we acknowledge that there's some number we want to get to is there anything that we can do to counter act the effect of c o two greenhouse gases all right you're looking at this you want this observed warming to go back so here there's two things that you can do to try to get it back there what can you do yep one thing that you could do is drive this back to zero so that we're not emitting net anymore greenhouse gases c o two in the other greenhouse gases and you're going to get pretty close to the same temperature that you had before the effects are going to keep going on for some hundreds of years where degree warmer now so we would still be a degree warmer than than we used to be but otherwise we'd be ok what's the other thing you might consider doing the other thing has been proposed is you we have this right where it is a member it's going to keep growing but instead you put in and you keep increasing the amount of particles as a result these are the two ideas behind geo engineering so this is from a magazine new scientist it's a really nice image and  it's kind of confusing but they're talking about all of the different things that you could do intentionally to the earth system to try to get the temperature back in balance so largely it falls into two blocks the two blocks that you guys just identified one of them is carbon capture that you somehow find a way to grab that c o two the other greenhouse gases out of the earth's system and find a way to sequester them there's all kinds of different things growing more trees you might create blooms in the ocean where backed form and that carbon gets eaten up and then it falls out of the system you could find trees cut them down cook them down to charcoal and then bury it and then grow more trees and keep doing this to p two up so that's called bio char and that's in the lower left so these are all ideas of carbon sequestration in the upper right of the ideas of putting more particles and more clouds into the atmosphere and so we'll talk a little bit about both of these if you read the news or you hear about geo engineering you might think about this is something that you know these scientists are just coming up with today the crazy scientists talking about geoengineering turns out geo engineering is not a new concept so this the quality of our environment deliberately bring about countervailing climatic changes so this is one nine hundred sixty five you might hear that there's this huge debate about climate change going on during the johnson administration they have a report that they're already talking about climate change happening because of the increase in c o two because of fossil fuel combustion in the environment and they're talking about can they do something about that kind change a countervailing technology a geo engineering solution they talk about raising the beat oh of the planet so they've already figured out that things like clouds and particles reflect sunlight back into space and they're talking about can we do something to raise the beat of the planet can we make the planet more reflective and not talking about particles though they came up with a pretty wacky idea they wanted to throw a white ping pong balls on the ocean so i'm not making this up this report is you can jump on google and find this thing so they realize that water ocean water is pretty dark it absorbs a lot of energy so they have this idea that they're going to make a lot of white ping pong balls they're going to throw it on the ocean and that's going to reflect sunlight back into space they're going to have to be very reflective so you know  solution so it turns out that we have as a country tried to figure out solutions like this since then this is a report by the national research council the national academy of sciences so this is a nonpartisan body that writes reports they bring experts together and try to figure out solutions to things like climate change so they wrote this report this is about carbon dioxide removal carbon dioxide seaquest ration a couple of years ago and so they know again that even as early as the one nine hundred thirty s people were understanding that c o two was responding to human activities things like deforestation c o two being put into the atmosphere atmosphere an and even by the one nine hundred seventy s people were talking about trying to grow more trees to pull that c o two out or sequester it from smokestacks that type of thing again this is the one nine hundred seventy s so if anybody tells you that we're having this huge debate and there's all this uncertainty about climate change there are a ton of people that are working on this fifty or more years ago now almost one hundred years ago and some of those cases this is not new stuff not only that but it's not science fiction there's actually places on earth that are already actively doing carbon sequestration so this is a natural gas facility extracting natural gas in the north sea that natural gas is coming with a lot of c o two normally what people would do is extract the natural gas and just dump the o two in the atmosphere so this is being run by the norwegians and what they said is that's not acceptable you have to find that c o two you have to extract it remove it and then you have to find something to do with it and so what this group did is they forced it back down into the oil and gas wells and it appears to trap it this is been going on for a number of years now and it's stable there's nothing that's that's going on it actually helps with the gas recovery and so this is technology a technology demonstration of what you could do in a case like this the couple of minutes that i have remaining i'll just talk about this idea of adding particles to the atmosphere so it turns out that there was not just one of these reports written a couple of years ago the last one member was carbon sequestration there were actually two written this one's called climate intervention reflecting sunlight to cool the earth and so the first report talked about removing that c o two the second one talked about ideas for putting particles and clouds in the atmosphere i always think this is kind of funny going back to my students this would be like me assigning a final project and the students are free to give me two final projects has anybody in this room ever handed in two final projects instead of one when you asked for one i didn't think so the group said the reason that they were doing this is that they felt like these two things could not be put into one report carbon sequestration actually is based on science there's an understanding of it there's been some examples done there's been a number of years people have talked about these topics and investigated them but this idea perturbing the atmosphere in a very unnatural way putting more particles there putting more clouds there is something that we don't really understand when i say that another way we have a history of seeing c o two rise around this planet we know what it did to temperature what it did the plants w humans remember we've got this record you go back ten years and it was at a certain level twenty years another and so on so if you took that c o two out we would know that we would just run back down that same path very close to that same path we don't know what the air system would be like if we put a lot of particles or clouds in that shouldn't otherwise be there and that's what the authors of this report said they talked about the risk i'm just going to very briefly tell you about what some of those risks are if you put more particles in you get more clouds what do cl often do a rain or they snow not only that but it rains or snows where those clouds are that also takes water out of the system so it changes the precipitation in other places and so these are some simulations if you actually put more particles into the atmosphere to try to change the climate what would happen there are certain places that would get wetter there's also certain places that would get drier so if you just that thermostat and you want the temperature to be something what you also do is create more rain in some places and you create more droughts in some place you might be happy with the temperature would you be happy if it didn't rain any more in boston no probably not this is one example where they're talking about seeding marine clouds making more clouds over the ocean when they where they won't affect humans so much the hot colors are droughts anybody know what this is here is the amazon rain forest this produces a large amount of the oxygen that we breathe on this planet is where a lot of the plants are this is an extreme drought caused over the amazon because you're trying to change the temperature of the planet i'm very skeptical of this is a scientist when i say that you should be to those of us that are old enough to remember the ozone hole this is because of particles of material getting put into the stratosphere that increase in particles that increase in clouds would be a decrease in ozone that ozone protects us from hard sunlight ultraviolet rays which cause skin cancer ozone going away temperature ok more skin cancer anybody want to make that trade ok i don't either just throwing these out there for you one of the one that's interesting in this got brought up with respect to plants is that if you put those particles in the atmosphere causes that diffuse radiation we talked about before solar cells like direct sunlight they don't work well with diffuse radiation so if you did this you would get rid of one of the room nubile energies that you're depending on to get you out of this problem when to say that once more you put particles in the atmosphere margin on solar cells goes away you can't generate solar energy the same way it becomes ineffective and so you're not able to get the renewable you would still have wind resources and things like that all of the solar farms that you see as you drive the two west in places like that all the ones in the southwestern us forget it not going to work anymore so these are huge issues if you tried to do this so i'll leave you with this sort of the pros and cons of just know that the problem with modification this idea of more particles and clouds is that it has a lot of risks some of which are known and some of which are poorly known whereas carbon sequestration running back down getting rid of that c o two is a relatively well understood process something that we've experienced before we have records of so with that i'm going to say thank you for your time and i know we're right up against it but i will stick around as long as you guys have questions so please feel free and thank you it's what is the quote about a little bit of knowledge is dangerous so you guys got it right you looked at that one pot that i put up and you said there's two things you can do and you came up with the fact that you could put more particles or clouds in the atmosphere and so if you have a little bit of knowledge you come to that conclusion if you have a little bit more knowledge you start thinking about ocean acidification you start thinking about regional droughts you start thinking about health the facts you so thinking about solar power generation and so on and now you get to the point where maybe this doesn't become such a great idea anymore and so if you're going to sell it you can sell it by just talking about the positives but you do have to ignore the negatives and so very often now you guys will be paying attention but if you see an article come out about it you can ask yourself well are they talking about this are they talking about that and so on and certainly you can imagine if i could give you a cheap technology and you didn't have to change your energy infrastructure at all there's a lot of different people that would want to still continue to do that so that also factors into the they are at a quick note about that earlier but i glossed over it in the interest of time but we think that there is more we know there's more particles now but we also believe that the cloud coverage has changed we also know that the brightness of the clouds has changed and so so we believe that there are different globally but we can even see there are different regionally so you can go to places that have pollution flowing out of them places like southeast asia versus other places that have the same meteorology but are less particles being put in and you can see the changes in the clouds from the to put between the two regions so so yes they've absolutely changed oh here in boston so it's hard to tell what they've done in boston one of the reasons if you go back in time we don't have very accurate records of clouds going back one hundred years or two hundred years you know we have notes that people took we also didn't have satellites so so most of our understanding of changes has come since the satellite record since we had coverage and so those are changes that have happened in the last thirty or forty years and there haven't been huge changes in boston we've gotten actually a little bit cleaner in boston where as we can see that signal in places that have increased pollution a great deal or places that have decreased pollution a great deal boston is not actually one of them yeah no