Climate Science and its Fundamental Role in 21st Century Challenges

[00:00:00] Speaker 1: okay okay well um thanks all for coming um it's a great pleasure to introduce us our very special speaker today but before i do i just want to mention that this is being recorded so any questions after the presentation just wait for the mic this is being as i said video video video recorder just of the presentation and the voiceover and also aspects of this lecture have been published and we're going to put that on the climate the center for climate sciences website so you'll have some sort of written document of to a large extent the lecture there's probably some things in here that's that's not quite covered but nevertheless it's a very great pleasure to introduce um of dame julia slingo who's not only a colleague of mine been a colleague of mine for quite a long time but she's also a kind of a dear friend um and so i've got a cv here i just don't quite know what to say it's kind of hard to introduce uh her she as you probably many of you know she was until about two years ago two years ago a year ago two years ago the chief scientist for the med office um she has all sorts of accolades and while she was a chief scientist of the med office she really was really was the sort of shape the weather and climate sciences of the uk was one of the most influential and designated one of the most influential sciences and you scientists in the uk at that time she has many sort of accolades she's a member of foreign member of the national academy of engineering u.s she's a fellow of the royal society she has been awarded the obe and also i have to read this because i just call her the dame but the dame of the order of the british empire she has more flipping um letters of the alphabet attached to a name than there are letters of the alphabet so i can't go through all of these uh there's a british thing to do they have these letters attached to your name uh she's also an honorary mem honoree uh has an honorary degree in eight different universities she's not going to quite catch sir david led so adenborough who has 35 honoree degrees but you know it's a kind of a really impressive impressive um resume she's also designated and this is not just the term of endearment she's also designated as a national treasure um so um she is a national treasure but she's actually literally a national treasure and um so you know it's a great pleasure to introduce her but before i bring her up i also want to note a couple of special members in our audience too the general the um consul general from of the uk um michael howells is in the front here and the deputy consul general um colette weston is also in the audience here so when the national treasure comes to these foreign shores they have to be in attendance i guess okay so it's really a great pleasure to introduce julia it's going to be a fascinating talk i think we'll all enjoy it and um welcome [00:03:19] Dame Julia Slingo: thank you very much graham i'm not sure about the national treasure bit but anyway um it's really good to be here and and although i'm retired i'm not completely inactive um i do spend more time in the garden and sitting on the sofa than i used to and singing in choirs um and for some reason um but i thought it would be really interesting to give you a sort of a sense of where climate science is where it's come from actually because sometimes we don't do that and talk about two cutting-edge pieces of research that i initiated in my final year or say when i was chief scientist so i want to talk about climate science and actually give you a sense of its fundamental role still in in addressing 21st century challenges it's very easy for us to say if we're thinking of climate change that we've got the answer and all we need to do now is to fund all the uh technologists and engineers to find all the solutions well that's not that's not true there is a lot of fundamental climate science still to do and we need to remember that but let's start with sort of just saying what is climate well uh this is a quote not by mark twain as is often assumed but um by by a geography professor climate is what you expect weather is what you get and so when we think about climate we have to actually think about the weather and this has been really um my theme ever all my time at the met office where we did everything from early weather forecasting to long-term climate change was that the fundamental science is the same and actually if we're going to talk about the climate we have to talk about the weather because the way we'll feel climate change is actually through extremes of weather it won't be the two degrees c rising global mean temperature for sure um so this you'll see this theme running throughout the lecture and climate science is about understanding the earth's climate of course through a combination of theory observations and computational models i'm going to tell you quite a bit about the theory and the long uh legacy of that theory i'm going to talk not very much about observations at all just touch on them and then suppose spend most of my time talking about climate models and weather models and how we can use them to address 21st century challenges so we're going to have a bit of history british history to some extent but also american history because i think there's quite a lot of us who work in climate or in related fields who probably don't know some of this stuff and um we're going to start with halley of halley's comet and you know this was the age of polymaths people dabbled in all sorts of things and he dabbled in trying to understand the trade winds and of course the uk being a maritime nation they knew all of they had sailed the world seas and they knew about the winds and this is a very iconic picture that was published in 1686 showing the winds the trade winds the winds of the world and where he's actually put these little dashes here is where the wind reverses with season so this is the monsoon they knew about the southwest monsoon and the northeast monsoon and halley pondered about well why do we have these trade winds that converge pretty much on the equator and he he argued that it had to be to do with the passage of the sun during the day as it went round the equator it warmed the air up as it passed and they drew the air in behind it as it as the sun went past and so you had easterly winds um and that was in 1686 in the uh philtrans of the royal society the royal society was founded in 1660 so this is one of its very early publications and that's basically what they thought at that time that it was just to do with the passage of the sun you have to go forward then about another 50 years to 1735 and george hadley who actually postulated that it was more to do with the conservation of velocity how the air as it moves from the tropics towards the equator having a less velocity of diagonal rotation than parts of the earth that arrives at will have a relative motion contrary to that of the earth in those parts so he'd already worked out that it was to do with the fact that we live on a sphere and that velocity was conserved and he also postulated that the air converges in the hot regions the air rises and descends somewhere else and hence the hadley circulation he actually wasn't a particularly eminent scientist and i couldn't find a picture of him anywhere you can find pictures of other hadleys but george was obviously um maybe this was his his big work but anyway very very interesting but there we are in 1735 we've got at least the essence of the hadley circulation and then you have to go really quite a long way forward another hundred years to coriolis who talked about the movement of objects within a rotating frame of reference and coriolis didn't actually think about a rotating sphere the planet but of course his ideas were pretty quickly taken up by an american in this case ferrell who worked out that because of the coriolis force that if a body is moving uh if it's moving to the into the northern hemisphere it's deflected to the right and then the southern hemisphere to the left and that actually really then did explain the trade winds and indeed the mid-latitude westerlies which were known then as the passage winds so you had the trade winds with the easterlies and the passage winds for the westerlies and he of course worked out that it was the absolute angular momentum and not the absolute velocity that explains the winds of the world so ferrell was pretty important in actually establishing that because we live on a rotating sphere we're going to have uh easterlies and westerlies interesting it was published in the nashville journal of medical of medicine and surgery which probably says there wasn't much in meteorology going on in the us at that time who knows it's extraordinary isn't it um and then we have to go forward to rossby so here we've got this we've explained the trades and we've explained the the the jets but actually it was rossby again working in the us swedish scientists working in the us who i think of course set the foundations of dynamical meteorology and oceanography and he established the theory of planetary waves what we call rossby waves as a result of the earth's rotation and of the stratification of the atmosphere or the ocean and these rossby waves basically set the scale of the general circulation that we know today so this is rossby's original drawing of rossby waves and within those you get wave breaking you get the formation of lows and highs sets the scale of our synoptic systems this is actually a picture of the flow at in the middle troposphere in the very cold spell in 2014 and basically what you're seeing here are these characteristics in this case quite uh well amplified rossby waves here so here we are we're in the mid of 20th century before we really have an understanding that it's the rotation rate of the planet and the stratification of the atmosphere that sets the scale of all our weather and hence sets the scale of the climate and those rossby waves are modified of course by the presence of mountains and of the ocean the presence of the oceans versus the land but fundamentally it's about earth's rotation so there are some big constraints on the nature of our weather and climate from some very fundamental properties of the planet so that's where we are with dynamical meteorology we go back into the 19th century and there was another group of physicists in this case who were looking at other aspects of of the planet its energy balance and here we've got john tyndall who was working on trying to understand they were very puzzled as to why the earth was so warm because if you do a straight energy balance for a black body the earth should be quite a lot colder than it is and it was tyndall really who was able to explain that the atmosphere and particularly water vapor is a very strong greenhouse gas and that that's trapping radiation but he also showed that these gases were emitters as well as absorbers of radiation and that's really important for understanding the energy balance of the planet and here we are 1861 round about the same time i guess as ferrell who was working on the trade winds and the mid-latitude westerns we have this paper on the absorption and radiation we would say emission of heat by gases and vapors and on the physical connection of radiation emission absorption and conduction and conduction and we would call that transmission of radiation again in the royal society and this is tyndall's experiments a very well-known picture where he actually measured the infrared effects of various gases so here we are in 1860 understanding that uh we have the sun's energy coming in but that actually it's gases and vapors that actually trap the infrared radiation and keep the planet warm and this idea was taken up actually by uh arinius who was a nobel prize-winning physicist from norway and in in actually in 1896 he made the first prediction of global warming and then he published in his book on worlds in the making in 1908 uh this statement about understanding that the enormous combustion of coal was going to lead to an increase in the amount of carbon dioxide in the atmosphere so the theory of anthropogenic global warming is not new um it's been known for a very long time and he he postulated that if you double uh the co2 concentration you're going to get a temperature rise of four degrees c which is actually still within the ipcc range it's at the upper end but actually we might think that it would probably he may be actually not far off being right but interestingly arinius then went on to say by the influence of the increasing percentage of carbonic acid co2 in the atmosphere we may hope to enjoy ages with more equitable and better climates especially as regards the colder regions of the earth ages when the earth will bring forth much more abundant crops than at present for the benefit of rapidly propagating mankind so he had a very positive view of the effects of global warming from very much just a sort of i think a a non-dynamical view of what the climate how the climate system works and and uh you know that pretty well and of course at that stage in the early part of the 20th century people were much more concerned that we were going into another ice age um than anything else so this was probably seen as quite a good thing so here we are we've got the dynamical basis of the climate we've got the energy basis of the climate but of course um there's an interesting other little story that was going on in the british empire which we often don't hear about and this is the story of the british in india and this is henry bramford who was uh who went to india as its first uh director of the indian met department and uh when he got to india he thought gosh this is great here we have order and regularity of the climate uh as prominent in india's atmospheric phenomenon phenomena as our caprice and uncertainty those of their european counterparts what he was talking about was that when he looked at his anemometer he could see the diurnal and semi-dianal pressure waves was pretty well all the pressure variation he got in india whereas where we live in the uk uh the pressure is going all over the place and the weather is constantly changing and he thought that he'd found in india a special place where he could understand meteorology and uh i won't read it all um but it's sort of sabering to think that when i was working in monsoons on the indian monsoon in the 1990s we thought that actually the complexity of india's position with its uh relationship with the indian ocean with the himalayas with all the other uh aspects of the circulation the india was probably the most difficult place to understand the meteorology rather than the easiest anyway blanford thought he'd got a great place where he could do something but of course he got he came very rapidly unstuck because we had the global famine uh the great famine of 1876 to 78 where there was a massive failure of the monsoon rains and here we see actually again the conjunction of politics and science reminiscent of where we are today our science is very much in the political frame and it was in at the end of the 19th century because britain um relied very heavily on india for its cotton and grain harvest and indian taxes and to pay the dividends to investors was absolutely dependent entirely on the monsoon rains which actually are mostly incredibly stable so everything had been geared to the regular return of the monsoon rains and india was a vitally important asset to the british empire so blanford was told you've got to sort this out we can't have this anymore we need to control famine through climate prediction we need to know what the weather what the monsoon is going to do so that we can govern india more effectively so they spent a blanford then spent a lot of time thinking about is it to do with himalayan snow cover they thought it was the 11 year solar cycle had something to do with it in fact later on we know that this was one of the biggest el ninos ever observed was happened in these years and el nino leads to very often to failure of the monsoon rains but he didn't know any of that although he did know that drought in india was also concurrent with drought in australia he had a friend todd in australia who told him that and then we come to one of my great heroes sir gilbert walker who turned up in india at the beginning of the 20th century and he really got to grips with this and pioneered statistical climate forecasting which was basically how we did climate prediction seasonal forecasting all the way through the early the first half of the the 20th century indeed in india is still done in this way he called it seasonal foreshadowing he didn't call it forecasting i think actually foreshadowing is rather a good word because we never know quite what the seasonal forecast is going really tells us but he formed he performed masses of statistical correlations he had a huge number of staff doing all these analyzing all these data and he said i think that the relationships of world weather are so complex that our only chance of explaining them is to accumulate the facts empirically and that's true until we come to the really the the age of supercomputing when we now have a different way of of understanding things so he he discovered the these these various oscillations but he also sort of set the idea that the climate of one region can be heavily influenced by the climate of another so in other words when you look in a region and at the variability of the climate in a region you have to understand it within the global context of these oscillations what we now call teleconnections so this is the beginning of understanding climate variability and of course it came all came together with with bjerkness in the 1960s who had been working on el nino and the ocean and realizing that el nino was a couple phenomenon and that you had to have a change and that it was linked to this thing called the southern oscillation which gilbert walker had discovered which was where why india had drought when there's an el nino and the two things came together and we got the phenomenon the the the uh motor climate variability that we call the al nino so the last year oscillation and actually it was bjerkness who realized that actually when you perturb the ocean temperatures and the circ atmospheric circulation in these ways you turn you perturb the overturning cells across the tropics which he named the walker circulation so the hardly circulation is the north south the walker circulation we think of as the east west and so this is really then we really have this concept now of the ocean atmosphere system as being critical for understanding the climate and then of course we come to co2 and here is uh the latest curve uh going up to to december this year um and this of course is is keelings known as the keeling curve for mona lower i joined the met office somewhere around about here and writing the first radiation codes and cloud codes to go in our latest climate model and i wrote a paper somewhere around about here which was on on cloud feedbacks and water vapor feedbacks on a doubled co2 world in a very simple model was published in a book called carbon dioxide climate and society i thought this was a bit of fun an intellectual exercise i little knew that actually what we are observing i think we used to use 320 as the number in our climate model then that actually we would be way up here at 410 in my lifetime and that this curve effectively represents the big one of the great challenges for society now so this has been a massive this has been a huge story for climate science through the the past 40 years and critical to all of that of course has been the way in which we've observed the planet when i started in the met office we were just getting the first satellite images i did all my early work plotting radio sonder sense and thinking we had very little understanding of the global planet the global earth system now of course we know a vast amount about it and we're continually as i say actually giving the planet a health check and and of course jpl nasa been heavily involved in in quite a lot of this so earth earth observation has given us enormous insights but actually i would argue that all observations do is tell you what is happening and it don't they don't necessarily tell you why it's happening so the other big change of course has been the development of climate models which is where i started my career building the first climate models in the uk and just because i think it's a general audience i just want to say a little bit about what these things are because not everybody understands them they basically simulate the climate system and actually the weather based on some very fundamental laws of physics and they help us to explain how the climate system works why it's changing and what our future climate might be like so i often call this my laboratory so as like any scientist i want the best laboratory and that i can get my fingers on so i want the best model and i want the biggest supercomputer because actually the skill and the usefulness of climate models is heavily tied up with the increase in supercomputing power and i was well known in the uk for going to meeting with funders and ministers and saying i need more money for supercomputing and i did manage to get 100 million out of the uk government while i was chief scientist for arguably one arguably what is still the biggest machine dedicated to weather and climate prediction and so you know that's what you do i want the best laboratory because this is where we test ideas so these things basically what we do is we cut the world up we cut the atmosphere and the oceans up into volumes and typically in the horizontal the grid squares have up to now have been around 100 to say 50 kilometers so quite coarse and we have about 85 slices through the atmosphere so you're producing hundreds of thousands of volumes which you then describe with their physical properties and integrate those properties forward in time using some fundamental physics they're big codes the latest unified model code at the met office was about two million lines of code and it they need machines that are several petaflops to run and they produce a vast amount of data so but actually what's behind them all well you know it's actually classical physics so when you actually look at what we're doing within these models we're actually back to newtonian newton's second law of motion we have to add in the coriolis force which makes it slightly more complicated because we're on a rotating sphere but it's fundamentally force equals mass times acceleration and we have used and not so much now this concept of balance hydrostatic balance and but fundamentally at the growth scale that describes why the pressure decreases with height it's a balance between the vertical pressure gradient force and the pull of gravity in very high resolution models now we don't use that balance because in systems like hurricanes and thunderstorms there isn't a balance instantaneously they're very non-hydrostatic mass continuity quite simply what comes in at the bottom has to go up and come out at the top ideal gas equation everybody knows that from basic physics first law of thermodynamics leading linking heating to changes in the wind now this is where earth's climate particularly in the troposphere gets really interesting because the earth's temperature is such that you can have water in solid liquid or vapor form and when you change from one form to another you release or take up latent heat and so you can actually move heat around the system through moving water around the system and then changing its state and this is in fact the latent heat release when clouds and rain form actually dominates the earth's heat engine so that's why our and we'll see that in a minute this is why understanding how the atmosphere and those climate works is so complicated because we can carry water in three forms and here's a class is clapper on equation which relates the the amount of water that the air can hold depending on its temperature and we often quote this equation to argue that as the world warms there's more water vapor in the atmosphere and therefore we can have more severe storms and then some very fundamental things to do with radiation the plank and stefan boltzman's laws that link thermal radiation emitted by block body to temperature and kirchoff's laws that link absorption and emission of radiation by atmospheric gases that's basically what we're doing when we build a climate model we're taking some very classical immutable laws of physics and coding them up to describe this the evolution of the atmosphere in the oceans and what you get out is something that looks like this so this is a simulation done actually rather a long time ago now and there are some probably some better ones around um at 12 kilometer grid so this was done on a very big machine and it's a representation of the infrared temperature the black body temperature of clouds and the surface so the white clouds are high clouds the black surface is looking down almost to the ocean if you're very careful you can see the sun come past there it goes and when the sun comes past the clouds build up and then fade away this is entirely simulated by the model from those equations the only fundamental constraints on this are the rotation rate of the planet and the solar constant how much solar energy enters the system this model is generating the water vapor in the atmosphere through physics and in in this case we would have given it the other greenhouse gases but not water vapor so it's actually working out its own energy balance it can see the mountains and so forth now if you're an aficionado of tropical convection like i am graham is you know that this is actually not very good that these clouds are not quite right the frontal systems in these latitudes are very beautifully described they're part of the rosby waves that i talked about earlier but the tropics is really quite difficult and the reason is that when you build these models and because of the computer power available to you you have to make your grid boxes quite large otherwise you just can't get the problem through the machine and so over the years we've spent most of our time trying to understand how to represent physics that goes on at scale smaller than the model grid how to represent their bulk effects and they're things like the boundary layer and turbulence and mountains atmospheric composition smog radiation probably uh one of the more tractable problems that we can solve but the bit that's really still a major challenge for us is all of this what's happening to the water cycle how does cumulus convection work how do we represent it how does precipitation form how do clouds form in polluted and unpolluted atmospheres and so we're still absolutely we have so much to do but we have actually i think some really interesting new breakthroughs in the last decade we've seen i think a new age coming for for climate and weather science from first of all advanced earth observation this is the a train but particularly what we call the active sensors in space that graham's been very much involved with have allowed us to look down into these clouds and see where the precipitation is formed and to understand in combination with other observation what the processes are they've actually transformed a lot of our thinking about how rain is produced particularly in convective clouds and then of course we've had uh this ability now to perform very high resolution simulations this is one we did a few years ago at the met office of super typhoon meggy at one and a half kilometer simulation and what you can see here starts from a very smooth field and the physics of the model generates all these interesting cloud structures just from the physics this is actually a remarkable simulation of this particular event with the cloud bands and so forth and if you put that along with this sort of information you learn an awful lot of new things about how convection latent heat release interacts with the dynamics of the system to grow things like hurricanes and typhoons and so on so this has been a huge breakthrough in the last decade and i think the ability now to do what i call computational field experiments to study in great detail this system for example which you could never do in real life you couldn't go and look at the four-dimensional structure of a system like that in every bit of detail to understand what it's doing you can with a simulation so this is really really exciting for our understanding of some of the fundamental physics that's going on and of course it's been for us in the met office this became part of our our operational system while i was chief scientist it was a major revolution in weather forecasting this is a an example of a forecast way back in 2012 this is the radar image here and this is the model forecast and this was actually a red alert in the uk for heavy rain through just where i live which is about here and um i was actually due to go to a garden party at the vice chancellor's house at exeter university and needless to stay i stayed at home i couldn't have got out of the town if i'd wanted to this was a very typical of the quality of forecasts and these colors are the hourly rain rates so it gives now a very very good sense of the flood risk and surface water flooding and it's just been an amazing advance and we've used the same models now to look at local climate change scenarios and shown that actually we could the potential for much more intense rainfall in summer in the uk is much greater than we thought from lower resolution coarse grained models so it's completely changing our perception of how we must adapt to changing rainfall patterns in the future with global warming so that's where we've come we've come all the way through that history of climate science the fundamental physics to being able to talk about local flooding and that's important because i want to now sort of say well how does that relate to the 21st century changing landscape and i'm going to put weather and climate risk because that was weather that we just saw there and this is a diagram i often use to talk about where our science fits it's very important that when we think about where the climate variability and change which is what i was working on the met office that we don't forget that these things are happening within the world that is also under major pressures from urbanization population growth and limited natural resources of particularly water water will arguably become the most precious resource on the planet i think in the next few decades so we have to look at it in that context and therefore it's no good to say well okay we've had climate change in the past or we've had these things in the past and and it was all fine the point is that the world is not the same as it was in the past there now an awful lot of us on the planet and we live in big cities and we depend on a globally interconnected economies and supply chains so we have to look at our science in that context and um and these things in this middle circle essentially influence the securities on which we rely for our health and well-being and again what's really important here is that we don't look at each of these in isolation you can't look at food security without looking at water security and so on they're all interrelated so we have to think now of our science in place within this broader context of the things that we rely on for our health and well-being and for the health and well-being and for the sustainability of the planet and therefore um you know i was i my feeling was that 2015 was really quite a landmark year in lots of ways we had paris first-time governments had accepted the evidence for climate change and agreed to do something about it we have the send-by agreement on disaster risk reduction and we have the sustainable development goals and all of those depend on a strong basis in weather and climate science and so you know this is sort of some grand words but actually this is very real and we see this happening uh now not not in the future with climate change so uh and interestingly if we wanted to argue the case for our science this is from the world economic forum last year looking at the likelihood and impact of the global risks and what's at the top uh everything to do with extreme weather events natural disasters failure of climate change mitigation adaptation are regarded as the most critical uh the top risks and some down here as well too but actually i think that's very striking so we have to advance our science and it's fortunate that i think we do have some new tools in the toolbox these are from my time as chief scientists uh but these are important this concept to now that we forecast across timescales seamlessly from near-term weather to what we call the extended range to the monthly to decadal actually this time scale the next year or the next 10 20 years is actually where a lot of people are going to make their decisions and then we've got long-term climate change but the idea here is that the same science the same modeling techniques go through all these time scales you add different things out here to do with the earth system that you don't need back here but the fundamental atmosphere ocean science is the same and likewise we've seen this just now this concept of seamless of prediction across space scales from the global models that we run in climate and in weather forecasting to get what we call the synoptic drivers of local weather through to what i was just showing you the regional predictions at one kilometer to give you the local meteorology and then feeding that into all sorts of impact systems to get both the probability of local hazards to give you impact scenarios and narratives this is flood risk in this particular case but this is the way the science has developed so we're actually in a place where i think we can do some useful things so just very quickly i wanted to just give you a couple of examples this is the uk in uh early part of 2014 and in december 2015 terrible flooding and i was very much at the sharp end of some of this being the chief scientist and of course what you get from the minister is well first of all is this climate change well actually when you look at the rainfall and river records for the uk for the last hundred years you can't say we have a hugely variable climate it was very hard to say it's climate change and then the minister went on to ask me particularly after this event he said how much rain are we could we get could we get three times the amount what is the plausible worst case for you clay flooding in the next ten years and you go how do i answer that and he wants the answer in six weeks so when you work in um positive policy related science you have to move fast so these were really really difficult questions they look simple he thought they were simple they're very difficult to answer so what did we do well actually i'm going to take you back to another bit of fundamental science and this is ed lorentz and his famous quote quote one flap of a seagull's wings may forever change the course of the weather and this has been the fundamental part of why we do ensemble prediction we never make one forecast anymore we make 50 or whatever because we know that chaos theory tells you that small perturbations grow and gradually change the sequence of the weather sometimes in a very constrained way and sometimes in a very broad way but you can also argue of course that if you take that concept there are lots of worlds that might have been during the period in which we've observed the planet but we haven't observed them because we didn't get the flap of the seagull's wings in one place or another so you have to remember that observations is own is only one plausible realization of what the world's weather could have done say in the last 30 years and when you accept that you then say well actually could i use them multiple realizations of the weather from simulation as paths that the world's weather could have taken but we happened not to observe so this idea that there might be black swans out there very extreme events that just could have happened if the weather had set up in a different way because of chaos theory if we chopped down a different bit of forest or done something different with our cities that's the flap of the seagull's wings so what we were able to do was actually to take we had 1400 years of simulated weather from 1980 to 2010 because of part of another project so we had 1400 simulated winters that were all perfectly plausible versus 35 observed winters so it was from 1980 to 2015 and then you can say well here this is for southeast england these are the the range of the observed monthly rainfalls during the winter and we've only got 30 35 samples and you can sort of plot a distribution but quite frankly the tails are not well populated here's the model simulations and they were quite plausible simulations the model was quite good actually surprisingly good it's quite a high resolution model and we've put in red the ones that lie outside anything that's been observed right and so you've actually filled up the distribution function much more effectively both at the dry end but here we're interested in the wet end and you've got quite a large number of events the wetter than anything you've observed in the current climate just from natural variability there's january 2014 the thames flooding which was an extreme outlier compared with the previous years but actually if we'd have this information we might not have been so surprised that it happened and there's one that's actually worse than that so then you can go away and answer the question that the minister wanted was well what's the chance and he wanted a one in 100 year chance well i don't know how you do a one in 100 year event when you've got about 50 years maximum data not sure but actually you can do the one percent risk so here we've got this is the percentage increase in rainfall above the maximum that we've currently observed and this is the chance of the event so and here's the probability taken from the simulations and we can say that actually at the one percent level there's a chance of having between 25 and 30 percent more rainfall 20 to 30 percent more rainfall it's not zero and it's not a hundred it's actually quite well constrained and every year you might expect there's a reasonable chance that you'll break a new record it's between five and ten percent if we had done that with only 35 years of data which is what we've got for the observations for the current climate with co2 forcing then you can see how unconstrained the tails of the distribution are you can't really talk about the risk of a one percent event it's anything across here and this is a big problem for most of the things to do with the insurance industry and many of the infrastructure investments we're having to work at one in 100 year events the industry the insurance industry works entirely on the tails of distributions which are not well characterized from observations so there's a real role here now for simulation to provide synthetic event sets that can allow us to populate or fatten up the tail as the insurance industry says to give better estimates of risks of extremes so this is a very exciting development and i think you know we're just beginning to explore this applying it to uh all sorts of aspects of of the world's climate from heat waves in china to uh heavy rain in the uk and and elsewhere so very exciting that's only one bit of the story though because actually what we really want to know is at the regional local level what are we going to do this is the thames barrier is it good out to 2100 is a good question in 2014 that 2013-14 the thames barrier was closed more than it was open it was closed most of the winter because of the extreme rainfall and extreme storms that we had so it was a bit of a wake-up call is how how well do we know these things and uh this is our number one risk in the uk is east coast storm search but how do you manage to how can you characterize that risk well we um started a really groundbreaking project while i was at the met office having experienced that those extreme events thinking about well how are we going to get a better understanding of the fully coupled near surface environment so the uk the thames is exposed to river flooding storm surge tides all those things so this was a project we started an integrated couple predictions for the uk at the convective scale it the port portents to relevance to people ecosystems and infrastructures this is what people really want to know about we're going to manage our risks so this is what we've built in the last three or four years published uh in in geophysical model development by hugh lewis who worked very closely with me when i was chief scientist and we built this one and a half kilometer model of the atmosphere the land the waves and the coastal shelf sea i think it's a first it's very very innovative this is not going to be operational i don't think for another five to ten years but very exciting just a little snippet of what we get out well this is sea surface height many of you won't know but the uk is pro experiences incredibly high tides this is the tidal range in here in meters from more than eight meter tidal range in many parts of the country this is the the tide propagating around the shelf sea of the um around the uk and so tides are an integral part of our environment not necessarily others the tides here we are from the shelf c model this is surface currents and we can see to be speeded up a bit the tides also drive very very strong surface currents around the coast and some very interesting uh coastal currents you can see when you're down at one and a half kilometers and the interaction of with the the shelf here is fascinating and there's been a lot of analysis of this we've uh added waves and here's a couple of examples of extreme wave height one up on the east coast here which is of the in the north sea this is an uncoupled simulation of the wave height this is the coupled in red and the observations in black so a fully coupled atmosphere ocean wave tide model gives you estimates that are at least half a meter bigger than you would get from an uncoupled model and half a meter when you're thinking about sea defenses is quite significant this is actually hinkley point where we're building a nuclear power station and this was another example i was asked what a one in 10 000 year event was for hinkley point when i was chief scientist that was interesting didn't know how to do that really but here's hinkley point very very different wave spectrum but again if you're if you're concerned about extreme wave heights really it's the only the coupled system that gets anywhere near the observations here's the work we've done we have a very complex river system in in in the uk this is our interactive now coupled hydrology and river flows this is part of developing a much better estimate of of river flooding and how we manage rivers um from the from the this very high resolution model some very exciting stuff we have a lot more to do uh including also the coastal biology and the and the health of the coast and we've started to work with other countries particularly singapore where the local environment is also very complex so i think this is this is a really exciting breakthrough so if we think about what the 21st century is going to require of us then i think you know thinking of environmental risk is going to pose major challenges to society the science of weather and climate lies at the core of managing many of these risks whether it's um through um simulated event sets and narratives sorts of things i've given you a sense of we have to get a better understanding of the coupled local environment in which we live and that i think is the next step for a lot of our science is getting down to that local environment level well i just wanted to end up because i'm here at jpl and it's nasa i wanted to end up by just saying a little bit about from leave the last word almost to pierce sellers because i he was very um i think inspirational many of us knew him in his early years as a land surface modeler and he went on to be of course an astronaut and here he is in the space shuttle and um he died as many of you will know of pancreatic cancer about two years ago and the year before he wrote a really i think fantastic piece uh in the new york times and this is what he said when we think about the challenges we face and for the future he said new technologies have a way of bettering our lives in ways we cannot anticipate there is no convincing demonstrated reason to believe that our evolving future will be worse than our present assuming careful management of the challenges and risks history is replete with examples of us humans getting out of tight spots the winners tended to be realistic pragmatic and flexible the losers were often in denial of the threat i met quite a lot of those losers when i was chief scientist people who uh senior people who denied that climate change existed and that it was all all a hoax they were in denial of the threat he then goes on to say as an astronaut i spacewalk 220 miles above the earth floating alongside the international space station i watched hurricanes cartwheel across the oceans the amazon snake its way to the sea through a brilliant green carpet of forest and gigantic nighttime thunderstorms flash and flare for hundreds of miles along the equator from this god's eye view i saw how fragile and infinitely precious the earth is i'm hopeful for its future wonderful piece by him there's so much more in that to read actually and so i think you know coming back to the beginning climate science is about helping us to live safely and sustainably on our planet and i just want to end with a bit of what might look like frivolity but it's not i think it's quite a profound message this is linus from peanuts and he's out there and he's on the beach and he's building this fantastically ornate sandcastle and i often think about that when i see climate impact assessments and the sort of information we sometimes give out to ministers we've built this fantastically complicated assessment with social scientists and engineers and so forth and it looks a bit like that we'll all have seen them but the problem is as he finds out is that the rain comes down and he says at the end there's a lesson to be learned here somewhere but i don't know what it is and those of you who remember going to sunday school might well remember what the lesson is of course is that a foolish man built his house on sand the rain came down the streams rose and the winds blew and beat against that house and it fell with a great crash and of course what did the wise man do the wise man built his house on the rock the rain came down the streams rose and the winds blew and beat against the house yet it did not fall because it had its foundation on the rock and what's really important here and one of the things that concerned me when i was chief scientist is that whatever advice we give to people who have to make decisions and and set policies that we need to ensure that the bedrock of science is there and this is so this is a really important message climate and weather science is not done it's a long way from being done and we have to be aware as i often was in talking to ministers in government to be really honest with them and say i can't answer that question because the science isn't good enough yet as we move into this world where we're going to be asked challenged time and time again about environmental risk we have to be absolutely honest and ensure that we get the investment in the bedrock science the sorts of stuff that you're doing here with earth observations the sort of stuff that my folk at the met office are doing with uh building better and better models we have a long way to go if we're going to provide the quality of information that we need to deal with 21st century challenges so that may seem like a bit of frivolity but the message i think has to be very clear so thank you very much for listening i've run on far too long um [00:59:57] Speaker 1: questions uh for about five minutes i know it's lunch time we're going to run it over into about five minutes or so for questions i'll wait for the mic because this has been recorded [01:00:17] Speaker 3: hi um i wonder if you have an opinion on what i perceive to be the fundamental problem which you're getting at here which is um you know my brother was in the australian civil service and eventually became became fairly high up as in second to minister um and his his perception of the problem goes something like this um technical person says to minister we have a perception of a problem with a certain amount of uncertainty yes and the minister says you want me to commit how much money to your [01:00:50] Dame Julia Slingo: confidence level yes um go away yes is there an answer to that um yes i mean this was obviously this is the root of a lot of the work that that we were doing in the met office and um and it's some to some degree it's about um language that we use so we shouldn't use the word uncertainty because that's not what this is i mean chaos theory is not uncertainty it's about probabilities and confidence so that was the first thing and then you have to sort of actually start to work with these people and look at the cost benefit ratios where's their decision point so that it's not just there's an uncertainty where is it that it makes it's important for you to make a decision depending on how much it costs and actually it's a lot about just educating people about how we produce these probabilities and how they should use them after all every every decision we make in life is based on we make a risk assessment you may not realize it but we all make risk assessments everything virtually everything we do but it's about how you've got to have that dialogue with the minister and actually that this one was a the the example i showed of flooding was a very very interesting uh discussion i actually sat with the minister he wanted to know how climate models worked once he he understood all that and he understood what we were doing and how we were couching it he could actually describe it not all ministers are as good at this um i think we can't get around this that that we have to work with probabilities but i would like to think that we can use um better words positive words like confidence um there are messages where you can say i'm absolutely confident that it will be like this and we can use narratives i mean i didn't talk about that too much but actually very keen on taking some of the tales of the distribution and building a narrative from what the simulation is telling us about how the weather evolved and therefore you can run almost like a test case of what your response would be to it within that narrative i'm not sure i've really answered your question very well but i mean this is this is this is the fundamental thing that we have to in all walks of life as we go through we're going to have to deal with probabilities and risk and it's about having the right dialogue at the right level and i think the main thing for me when i was chief scientist was to be absolutely clear that anything i said whether it was a probability or whatever i could justify the scientific basis for and so i think this is still for me the key thing that we have to be sure that we can go back to the science and say i can i can or i can't answer that question yet but not try and give a half-baked answer on probabilities that you don't believe in right i can give you a more difficult question [01:04:15] Speaker 4: so you're you're tied climate change to weather extreme events which are local in space and short in time yes what about structural changes like abrupt changes will happen in the past i know like younger [01:04:33] Dame Julia Slingo: dryers and so on yes what about this um well they would have been the same sort of thing i mean the younger dryers was driven by a completely different process and uh we would pardon it was global that's right but what the point here is that what we feel as individuals is not the global change but the change where we live and the weather that we experience that's absolutely true um the younger dryers yes it was a global change was a massive change um and everybody will feel it but actually at the place where there was at the the individual or the country level it's about the weather it's not about the global mean change so how that manifests itself in the weather that you experience if you work for the government yes [01:05:39] Speaker 1: we'll take we'll take two more one from duane i think there's one up the top there for example the [01:05:43] Speaker 5: sea ice in the arctic going away that's not a weather extreme it's more along the lines of what he's [01:05:48] Dame Julia Slingo: talking about for example yes i mean that's that is a good example because uh but there what to what who's going to be impacted well it's probably going to be the arctic the inuits and the arctic ecosystems and maybe the loss of arctic sea ice could have an impact on uk weather for example so that's that's an example of a a big change but actually we most of the changes that we're going to see are going to be uh along the lines of more extremes whether we want to call them weather extremes or extremes of climate variability one last question and we break for lunch i'm just curious can we [01:06:35] Speaker 4: engineer favorable scenarios by having seagulls flap their wings what did she say she said can we [01:06:42] Speaker 1: engineer favorable scenarios by more seagulls flabbing their wings um probably not chaos chaotic system [01:06:50] Dame Julia Slingo: doesn't quite work like that unfortunately you've probably got equal chance of being unfavorable [01:06:57] Speaker 1: precisely yes okay so i think we'll thank julia again for a wonderful talk i think it's i'm not sure thank you much it was fantastic thank you