 I'm Mike Lockwood, I'm a professor of space environment physics at the University of Reading and I research long-term change in the sun and how that affects us here on Earth. I started off, believe it or not, looking at aircraft ground radio communications and a lot of those are done through the uneyesed upper atmosphere, the ionosphere and then I started working with a radar system in northern Scandinavia that looked at the ionosphere called ICAP, it's a joint European project, a rather wonderful project actually, I really enjoyed it, we had a fabulous time and northern Scandinavia is a fabulous place too. But that brings in the aurora and then I began to realize, well associated with the aurora is a phenomenon called geomagnetic activity which is how much variations in the sun shakes Earth's magnetic field and I began to realize that we could use the historic data on shaking of the magnetic field because it goes back a long way right back to Gauss in 1832 when he built the first proper magnetometer. So there was a rich record of these geomagnetic fluctuations to tap into and I realized it could tell us something about the variability of the sun so by applying all the research I'd done on the ionosphere because a lot of that geomagnetic variation comes about from currents that flow in the ionosphere so all that research I did was really useful and I could unpick the elements in why the geomagnetic variation had changed into working out what so the change was and that's been a really useful constraint in in actually in the irradiance studies. The way one of the reasons why 20 years ago people thought the solar irradiance between the mortar minimum now might have changed quite a lot although it would still actually be quite a small radiative forcing compared to greenhouse gases but one people it was overestimated because people were drawing analogies between our sun and what they called sunlike stars. It turns out those analogies were nearly all invalid so it also turned out that the surveys that we used were very very limited very limited number of independent stars we used. When that was realized it was thought well hang on we don't have any way now of telling what the mortar minimum sun was like you know we used to draw analogies to some stars out there but if we can't do that what do we got. So my stuff on on how the magnetic field of the sun had changed became very very important because it could be used as a constraint on and a whole new generation of how the solar irradiance has changed between the mortar minimum now grew up based on fitting the solar magnetic field that I'd inferred from geomagnetic data so it provided a new way in and as I say those estimates produced a much smaller drift in solar output between the mortar minimum now than we thought before and the recent solar cycle has proven just about right. It was all a classic example of how in science you look for one thing and you find something else it really was. Everybody knows that climate is driven by our climate is driven by the sun and so it's not a difficult step to imagine that changes in our climate must be driven by changes in the sun. The problem is that changes in the sun are actually very very difficult and rapid changes are almost impossible and the reason is that our sun is very very large it's a huge ball of gas and the important part is the outer part of the sun about the outer third where you have it's what we call convection zone the large cycles of energy flow with energy brought up and then the cold gas and plasma falls back down in these huge circulation cells now the thermal time constant of that outer layer of the sun the outer third of the sun the convection zone is about a tenth of a million years it's just so much of it you can't heat it up and cool it down and what the sun emits is largely dependent on the surface temperature so one little calculation you can do is say well what if I turn the sun off completely I stopped all the energy coming out of the core from the fusion reactions and it gets to this bottom edge of this convection zone what if I stopped all the energy coming through into the convection zone then a hundred years later here on earth the amount of power we were receiving from the sun would have dropped by something considerably less than half of one percent all right and that's a complete switch off of the sun so it's because the sun is so big it's so massive you can't change its outside temperature and it's its outside temperature that determines how much it emits so it's pretty constant in that and in fact so constant we used to call it the solar constant we used to actually say the power output from the sun was was completely constant then we found actually it does vary a little bit it varies by about the largest variation we've seen is about one tenth of a percent okay and the reason that it does that is that you can get little surface features caused by magnetic fields on the sun so those surface features are the most well known ones are sunspots sunspots are quite big bundles of magnetic field coming up through the surface of the sun and they inhibit the energy coming up from underneath but for every big bundle there are lots of little ones and in fact a big bundle to breaks up into little ones and the little ones paradoxically appear bright they're called faculty comes from a latin for torches so for every sunspot there are a thousand faculty and so the net effect is that when there's a lot of sunspots on the sun the sun is a little bit brighter as I say only about a tenth of one percent we used to try to measure the what we got from the sun because we know the atmosphere changes that by going to the top of mountains and measuring but it's still not a very good measurement from up there and so really one has to get completely clear of the atmosphere into space to to do the absolute measurements of how much power we're receiving from the sun trouble is this absolute radiometry particularly from space is a really really difficult thing to do it's it's very very hard and we've had a number of instruments up over the years the difficulty comes in both intercalibrating those instruments so when one instrument dies and another one comes you have to make sure that they're they're well intercalibrated but actually also the instruments themselves degrade quite badly particularly this type of instrument and you can have one way that they could deal with that is they have two instruments on board one they use very frequently on which the degradation is high and one they use very infrequently so it stays nearly pristine and you can work out what the degradation is assuming the degradation is proportional to its use so it's a very difficult thing to do and it causes a lot of debate about how you put these measurements together and there's really two philosophies the swiss have the philosophy that you if because it's difficult you keep correcting you keep adjusting you've got to keep on top of keep calibrating it all the time there is a danger with that and that is of course if you keep allowing yourself to correct a data sequence you can turn into whatever you want and so the american philosophy is much more we just trust the instrument we put it up there and we see what it gives us but i actually believe that you can't necessarily do that because the instrument degradation in this particular case is quite high is quite a big problem so even with that though those two different philosophies it really comes down to the big difference between the what we call composites these where we've taken different measurements and tried to make a long data sequence those composites differ largely because of one event believe it or not and it's in a period between we had a good instrument on smm skylab that um we lost because we lost skylab crashed somewhere in australia um that was called acrim one and then acrim two was on a satellite called ur see our practice for research satellite and the idea was acrim two would be available as to take over before acrim one died so you had some overlap to intercalibrate turns out that because skylab came down early and acrim wasn't uh two wasn't ready there's a gap between the two so what they did was they went back to the first instrument they used which was something on an old satellite called nimbus seven and it's known that in the middle of that period nimbus seven had a pointing funny it stopped pointing in the right direction and the swiss have corrected for that and the americans haven't and that's why the big difference between the two all comes down to that one event so um and the evidence is a lot of treatment to try to prove that models support one or the other all the evidence is kind of supports the idea that the swiss have got it right so i personally think that the um the reconstruction from the world radiation center is p-mode it's a laboratory in in devils in switzerland and i think that's by far the best one myself uh there are other people that like the other one because it kind of gives them the result they want but actually when you look at it in detail the evidence really supports the swiss one if you look at total solar radiance which is what we call solar constant now we know it changes a little bit if you look at that the variation that you get out of the swiss the p-mode composite agrees much better with things like sunspots and cosmic rays and and lots of solar indicators are and but actually the best test is probably what we call solar magnetograph data um this is solar grab magnetographs measure the magnetic field everywhere on the surface of the sun and from that we've got some really nice model um they call it the satire model which i'm not sure is a good name for a science model but um it's actually very very good and it reconstructs how bright the sun would be just from looking at all the magnetic field on the surface and that very much supports the swiss composite not the american one we've had modern space measurements of total solar radiance and the magnetic field and the sun and things like that and magnetic field that leaves the sun and comes all the way to the earth in what we call the solar wind we've had measurements of those that are reasonably continuous and reliable since about the mid 1960s so i'll call that the space age so we've got really good information about how the sun has changed in the space age the problem is until very recently the space age was dominated by rather large solar cycles quite high solar activity um we've sort of just really come to realize that we've been living in what we would call a grand solar maximum and we know that if we go back a few centuries the sun goes into what we call grand solar minima and the most recent one is the well-known maunder minimum which we now know is was real and and there really weren't any spots on the sun and and uh and we know from uh isotopes that are modulated by the activity on the sun that we find in ice sheets or in tree trunks we know that the the sun goes up and down between these grand minima and grand maxima the question is what information do we have about how the sun has actually changed and the best record we've got is sunspots because they go through we they do exist from before the maunder minimum they're a bit sparse but we do have measurements there through the maunder minimum and we now know that despite the fact virtually no spots were seen for 50 years people kept watching so amazing testament to how patient some people are and then they started coming back again and they increased and as I say recently in the space age we had three very big cycles and so the challenge was try to interpret our recent irradiance measurements in terms of sunspot number so that we could reconstruct how the irradiance changed and an estimate's kind of changed over time quite a lot for a number of reasons and but they weren't really very well constrained what's very interesting is this last cycle the cycle we're in now we're just about at the maximum of cycle number 24 we call it it's really weak it's incredibly weak uh well it's about we haven't seen a cycle as weak since about 1900 and the irradiance has dropped on average but not that much and so actually for the first time we've got a bit of what we call dynamic range on the measurements so we can actually extrapolate back to the maunder minimum with a bit more confidence interestingly the numbers that have gone in to say the IPCC report are about right what I think has changed is that if you look in the IPCC report it will say that the level of certainty on solar change is medium I think that could now be changed to high in the light of the recent measurements of what's gone on in the last solar cycle well we don't have a proper predictive model of solar activity it's that simple and and the best model numerical models we have of the sun are what they call two and a half dimensional well which is a nice way of saying they're not three-dimensional okay and the sun is eminently a three-dimensional body and that kind of tells you where we are with solar modeling we don't have a predictive capability so all you can do is fix on some patterns and there are some tricks that you can use to predict maybe five years in advance and the size of a solar cycle seems to be related to the magnetic field at the previous solar minimum and you can use that and that seems to work quite well in fact but we don't we still argue about why that is working so we don't have an understanding that gives you a proper predictive capability of solar activity which means that it's kind of open season for you know having a go because anyone prediction is as good as bad as anyone other one and so it's quite fun to line them all up and see who got it worst wrong and who got it very at best and things like that you're not really learning much about the physics of of solar variations by doing that quite frankly and the way to go is the same way the climate science has gone we've got to have proper predictive models of of solar dynamics before we can we can start to do that and we we just quite a long way from being able to do that so I think that's why people like doing it is that you know it's like gambling on the horses you know it could go any which way there is a whole area of science called space weather and that is to do with how modern technological systems are subject to solar activity and the effect of a very large solar terrestrial event on modern life could be quite profound I mean satellites are at risk communications are at risk all sorts of things are at risk so it is quite valid that we worry about that it's not so valid to worry about it in terms of the solar influence on global climate because quite frankly nothing fits the altitude profile of the warming is all wrong for solar warming the difference between day and night has not increased as you would expect if it was solar irradiance induced the the seasonality is all wrong okay in fact we've seen more warming in winter whereas if it was the irradiance increase you'd get more warming in in summer so nothing fits no it really doesn't fit at all and and there have been one or two studies that have tried to make the wiggles fit the solar variation but when you look at it properly with proper statistics you find that there's no statistical significance there at all it's if you have enough free variables you can fit anything so so I think from the point of view of global climate there really isn't any major issue at all but there is one thing that I'd like to point out and that's the difference between global climate and regional climate because I do think there's a growing body of evidence that solar activity variations can influence particularly winter climates in certain parts of the world and those certain parts of the world of the American continent and here in Europe in particular both those places get cold winters when solar activity is low and that that's a seems to be a statistically significant result it's not a global effect because if it's cold here and in North USA it's actually warmer in Greenland and Canada and in the Mediterranean there's what we call a quadrupole pattern that keeps appearing and it seems to have a good relationship to solar activity now why that matters is an awful lot of the anecdotal evidence for long-term solar influence on climate comes from early meteorological measurements made in Europe particularly in winter time in Europe and so if one says haha this is indicative of a global trend you're actually got a big problem because actually you're selecting a very specific area where there may be something funny happening okay so as I say if we get colder winters in in in Europe then they'll almost certainly be warmer in in Greenland it's to do with meanders in the jet stream warm air goes up to Greenland and we get the cold air coming down from the Arctic we call them blocking events because it's a this big meander in the jet stream is called a jet stream blocking event and it looks like through the solar ultraviolet effect on the stratosphere this might actually be real I think it is I think the evidence is pretty but it's contentious there's big scientific debate about it but what there isn't a scientific debate about is whether it's a global phenomenon he's not a global phenomenon and as I say if there'll be a compensating effect it's a redistribution of temperature around the the north Atlantic and but it does impinge upon the global warming debate if people insist on using measurements from a small region at a certain season they might get something that looks contrary to the consensus view it isn't really it's their assumption what's wrong is their assumption that their regional seasonal measurement actually is telling you something about global change we did some research I actually worked with the the main guy and at PMOD in Davos in in Switzerland a guy called Klaus Frohlich and we were able to show not only had his version of the solar irradiance been decreasing since about 1985 but every other solar indicator had so the in fact cosmic rays had gone up which means the solar activity that keeps cosmic rays low had gone down sunspots had gone down everything had declined since about 1985 now I know we've had a few years of so-called hiatus in temperatures but essentially they they've risen and flattened off but that flattening off was much much later so if even that flattening off had something to do with solar it's a very long delay okay before anything happened so unless you invoke an incredibly long response time constant that then you couldn't explain how the temperatures kept rising in in on the in the global average temperature and yet all the sunspot activity indicators were declining the only way to do it was to invoke this incredibly long time constant that meant that the earth was like and that doesn't fit because we know for example volcanoes we know what the response time constant is we see the effect on global temperatures of a certain volcano pretty quickly and why would blocking out the light with a volcano have a different response time constant to actually reducing the the strength of the source of the light it just doesn't make sense so to me that was useful confirmation that that actually that the recent trends in in temperature were nothing to do with the sun they just didn't fit I have tried very hard in everything I write to make it quite clear that I'm not talking about global climate change and in fact I did a paper with the guys at the UK Met Office where we put I estimated what we took various estimates of how the total solar radiance would change if we went into a more under minimum within 50 years of now which is about a 10% possibility quite frankly and we could make very little difference to the overall temperature rise even when we put everything we could in all the weightings it still made very little difference so I have made tried to make it absolutely clear that I'm not talking about solar it's on global climate and there are good reasons to expect them not to be there and there's certainly no evidence that they're there no credible evidence anyone but I do think that it's quite possible that you can have these seasonal they're nearly all in winter that's the clue it's because the jet stream is driven by temperature differences between the equator and the pole particularly in the stratosphere so in summer when you've tipped the pole towards the sun that gradient is reduced and the jet stream is so the modulation the potential for modulating the jet stream is much lower than in winter when you've got a large gradient between the equator and the pole and that drives the strong jet stream but it does seem to weaken when solar activity is low because that gradient is lower and that makes it more prone to these meanders these blocking events so there's good reason to expect it the difficulty is getting the effect down to the lower troposphere where our weather and climate is but it's beginning to show up in in climate models that have enough layers up into the stratosphere that they go high enough they start to reproduce this sort of phenomenon so i'm pretty sure it's there but i also know it's not global i think we've seen that in the data that if we get a cold winter in europe it might be cold in washington but it'd be warm in north canada greenland and actually warm over the Mediterranean as well so this this quadrupole pattern that i talk about keeps coming up there is an alternative hypothesis to jet stream modulation to do with the loss of arctic sea ice that's certainly possible um i do know a lot of people are slightly worried about the evidence but i know a lot of people who are slightly worried about the evidence for the the solar influence on it as well so i think i think you take the both of them and you put them into the a folder mark really interesting needs further study that that will be my assessment of of both of them quite frankly um but i think it's interesting it's both interesting and it's quite possible and plausible so i do get quite often quoted as saying an ice age is coming what i actually have put a number on is the possibility that the recent decline in solar activity that we have observed could continue all the way down to the next more than a minimum and i'd say that it's somewhere between a 10 and 15 percent possibility that that could happen in 50 years i am certain it will happen in within 400 years of now um i'm pretty certain it'll happen within 150 years of now but 40 or 50 years maybe a 10 to 15 percent probability and that's a statistically worked out number by looking at ice sheet records and things and the problem is that in some people's mind something called the little ice age and the mortar minimum becomes synonymous i'd no idea how that happened because they don't even agree in dates the little ice age as a global drop in temperature from things like tree rings and things like that starts somewhere between 100 and well all sorts of estimates but certainly at least 50 years before the minimum starts okay i don't like the term little ice age at all to me it wasn't an ice age of any shape or form okay one of the things i've had fun doing is looking at a temperature record it's called the central england temperature it's measured some in a rural area between london bristol and manchester so it's well out of any uh you can the measurements are always taken away from urban heat islands unless they grow and things like that and um it goes right back to the 1650s okay now if you look at those temperatures from the mortar minimum uh i think it's statistically true that there are more cold winters then which is the solar influence on cold european winters that i think is is potentially there um but they weren't unremittingly cold and in fact the coldest winter in the whole 350 year central england temperature record is 1683 to 1684 um that winter the if you just shift on two years from there so still right bang in the middle of the mortar minimum you have the fifth warmest winter in the whole central england temperature record so the idea that the term the little ice age gives this impression that it was unremittingly cold you know all the winters were freezing well no actually there were some plenty of warm winters in the mortar minimum certainly in central england um the summers don't really show much difference between the mortar minimum you know so i hate the term little ice age and i think it's abused i think people use it to say it it wasn't an ice age of any shape or form it may have been a period of slightly lower global average temperatures but it wasn't an ice age and and there's plenty of fluctuation level around it so i think to me using the term is just playing with words it's building your argument on a misconception i i i think it's also quite useful to point out that if your logical argument is resting on the interpretation of a name given to something it's not a good argument okay i think i could call you know uh anything anything to try and make a theory stand up all right but it's just bad logic it's just bad sloppy thinking to say oh that was a little this was a little ice age and you know what think about it it wasn't a little ice age it was a period of slightly lower temperatures on a global scale maybe and as i say most the evidence for that comes from trees it's actually what we really know is a period where globally summers seem to have been a little less good well that's that's not an ice age by any means the winters were more variable if anything i think there are some really interesting questions we certainly anything to do with solar variability where does it come from if we're ever going to get on top of predicting it properly we're going to have to understand that so i think um there's a whole lot of almost catching up to do until we've got solar models equivalent to climate models um we we're we're never going to be able to get anywhere so um so that that's i think that's really interesting it's a very challenging area as well actually it's not easy but there are some good missions coming up like um there's a european space agency mission called solar orbiter and and that's going to be really really fun to look at that it'll fly over the poles and look at the sun every which way and we'll actually learn an awful lot about the solar variability from that and as i say modeling's got a big part to play so that that's one area um this whole area of how stratospheric changes because the stratosphere is undoubtedly under quite considerable solar control but how do you get how does this thin gas at the top of the atmosphere percolate down and cause anything in the troposphere um as i said i think the effects and not global i think they're they're regional and seasonal and and patchy and region and so one region changes in one way and the other the other but i think my belief is that they're there and that becomes a whole interesting area there's a really interesting area in in atmospheric chemistry um uh in that sort of area as well um that they're with the chemistry and dynamics of the of the stratosphere have not been mixed up together very well in models so that that that's interesting i recently became a grandad twice over and that they're wonderful kids i want the best for them i want the best world for them and i am seriously worried that actually if we don't start taking the threat seriously understanding it and understanding how we can mitigate control that then i'm really worried about their future