cc  >> This is the, I think it's the  seventh seminar series set for  the Wisconsin's Initiative on  Climate Change Impacts, Bracing  for Impact: Climate Change  Adaptation in Wisconsin seminar  series.  And WICCI, which is the  Wisconsin Initiative on Climate  Change Impacts, is a  collaboration between UW system  and the Department of Natural  Resources investigating how  climate change will affect  Wisconsin's resources and how we  can adapt to that.  So today we have two topics or  two talks and I'd like to  introduce our first speaker  Dr. Steve Vavrus.  Steve is employed as senior  scientist at the Center for  Climatic Research where he's  been investigating the behavior  of the climate system for the  past 20 years.  He received his Ph. D.  and master's degree in  meteorology at the University of  Wisconsin and his bachelor's  degree in meteorology at Purdue  University.  Steve is currently involved in a  variety of climate related  research projects.  Using numerical climate models,  Steve is investigating the  response of global and regional  climate to increasing greenhouse  gases, particularly how such  changes might affect polar  regions and extreme weather  events such as heat and cold  waves and floods.  He is also exploring the origin  of anthropogenic climate change,  the role of clouds in the  climate system and the impact of  weather extremes on human health  and infrastructure.  Here is our first speaker Steve  Vavrus. 

 (applause)  >> Thank you.  How's the sound back there?  Can you hear me okay?  Good.  Thanks for the introduction  Mike, and thanks to all of you  for opting to listen to Jonathan  and me instead of Billy Joel and  Elton John at the Kohl Center  tonight.  (laughter)  I'm not sure of your  reasons for that, but we  appreciate it.  I'd also like to thank my  contributors to this talk and  there are many listed here.  Within my center and CCR, Dave  Lorenz, Michael Notaro, Dan  Vimont, Chris Kucharick who's in  SAGE in the Department of  Agronomy and the and Ed Hopkins  from the Wisconsin State  Climatology Office.  And I'd also like to acknowledge  this beautiful backdrop.  This is an image that was done  by a Wisconsin artist, Diana  Randolph, as part of a workshop  in 2006, Climate Change in the  North Woods.  It was an effort to bring  scientists and artists together  to try to visualize climate  change so it's not just a bunch  of numbers.  And even though it's a beautiful  picture, it has some threatening  undertones to it. 

 It's actually her image of a  thawing Lake Superior and the  impacts that will have in terms  of shortening the ice cover  season and the impacts on skiing  in the northern Wisconsin  region.  So extreme events.  For any of you who survived last  summer around here I don't need  to convince you of the  importance of extreme events.  We had some devastating floods  in 2008.  Here are some of the highlights.  You've seen pictures like this  before.  Of course, Lake Delton  catastrophically draining and  large agricultural losses and  urban flooding and so on.  Just to remind ourselves that  this wasn't just a rogue  thunderstorm, but in fact was a  widespread event.  It hit northern or central  Wisconsin even harder than  Madison and, of course, Iowa,  Cedar Rapids, we saw lots of  images of its flooded downtown,  but notice too this affected not  just those two states but also  down state Illinois, Indiana,  Missouri and into Kansas.  This was a very widespread event  and it's important to understand  the mechanisms that cause these  because we expect that we'll be  seeing more of this type of  event in the future, as I'll  describe later tonight. 

 And if it seems like these heavy  rainfalls around here have  become more common lately it's  because they have.  These are the trends in extreme  precipitation, shown here as the  occurrences of at least one inch  or more precipitation, usually  rainfall, recorded from the  Madison airport starting in  1940.  So this are decadal averages.  You can see there's been kind of  a gradual upward trend, the last  two decades having the peaks.  But the 2-inch and 3-inch  events, the gully washers, those  are the ones that have been  increasing the most in this past  decade.  And those really stand out.  The 2-inch stands out more than  the 1-inch days, and the 3-inch  days stand out more than the  2-inch days.  And the peak rainfall last year  that produced some of the  flooding that I just showed was  about a 4-inch event at the  airport.  So very dramatic.  We don't know at this point  whether that's a true expression  of greenhouse warming or if  that's sort of a statistical  fluke, but what we do know is  that the climate is warming and  we have reasons to believe that  that warming will produce more  heavy rainfalls in the future. 

 Those of you who are regulars at  this seminar series have  probably seen a slide like this  in every single talk so I won't  dwell on it, but it shows the  warming trend, globally, for the  land and ocean as a temperature  anomaly relative to this  long-term mean from the 1880s.  And what I want to highlight  here is that every year since  the mid-1970s has shown in red  indicating that it's been warmer  than this long-term average.  And 2008 was, I think, the  eighth warmest year on record.  And so this something that we're  confident in as the global  climate change.  But what we want to know for  WICCI and for other purposes is  how this is reflected on a more  regional basis.  And since we're in Madison it  seems appropriate to bring up  this graph that shows Madison's  long-term temperature record.  This is from the State  Climatology Office.  This goes back even slightly  further than the other one, back  to 1869.  And you can definitely pick out  these year to year wiggles in  annual temperature around here,  and also some decadal  fluctuations.  But your eye can catch,  hopefully even without this  trend line, the warming that  we've seen in the last 30 or 40  years. 

 So there's been some  oscillations about this upward  trend but we are warmer than we  were during the 1960s and '70s.  Although you'll notice that they  were warmer years in the past,  especially in the '30s and '40s.  So this is the annual  temperature trend, but what  about seasonally?  Has this warming been happening  steadily in every season or have  certain seasons been dictating  the annual trend?  And this shows that it's  actually been winter, if we go  back to 1948 to present, that  has the biggest, most pronounced  upward trend, shown in blue.  Whereas summer, there's probably  a slight upward trend, but  you're hard-pressed to pick it  out very easily with your eye.  Spring and fall, the transition  seasons, also maybe a slight  upward trend, but the main  pattern is a warming trend in  winter over the past 30 or 40  years in Madison.  Now what about extremes?  How might these changes in  trends in the mean climate  affect extremes?  And to address this question we  can turn to some of the recent  work that Chris Kucharick has  done looking at cooperative  weather stations throughout the  state, very detailed maps he's  put together, and he's addressed  some of the extremes.  So on the left are the number of  nights in which the temperature  drops below zero Fahrenheit, so  very cold nights, and on the  right are days above 90, so hot  days.  And it's really interesting if  you compare these two.  On the left, if we look first at  the very cold days, it really is  picking up what we expect from a  warming climate.  That is, areas in the blue are  showing a decreasing trend in  the number of days of extreme  cold over this period. 

 Just a few pockets that buck  that trend.  And overall there's a decreasing  frequency of about a week to  three weeks from 1950 to the  present.  So a very distinct change.  On the other hand, you might  think well, okay, a warming  climate will also have more hot  days.  And that's what the climate  models are projecting for the  future, but we see here that  that's not really been the case  over the last half century.  We see some areas that have  shown an increase, in pink.  But we also see just as many  areas that are shown in blue  showing decreasing trends.  And although I don't show it  here and Chris hasn't put it on  this map, Chicago has shown a  decreasing trend in its number    of 90-degree days.  And so to summarize there's been  very little change in the number  of hot days in the last half  century but a distinct  decreasing trend in the number  of severely cold nights.  So that's what we've observed up  to now, but what about for the  future?  A hint of what's to come, this  is a good lead-in slide. 

 It shows the late 21st century  climate change projections from  20 different global climate  models from the recent IPCC  report.  And the top panel is showing the  temperature response annually in  the left column and then winter  in the middle and summer on the  right.  And you can see that every where  is shown in yellow or orange or  red indicating some amount of  warming.  And you'll notice that the land  is generally warming more than  the ocean.  And the high latitudes,  especially in winter, are  warming more than the lower  latitudes.  But I might say, well, global  warming, of course there's going  to be higher temperature in the  future if it takes place, but  what about precipitation?  That's not so obvious.  So a warming climate could  become wetter or it could become  drier or their may not be any  change.  So that's a more difficult  projection, and we can turn to  the climate models to give us  some guidance.  It's showing, or the models are  showing, generally a split  between northern regions  generally getting wetter by the  end of this century compared to  the end of the 20th century,  subtropical regions becoming  drier and that's even more  pronounced in winter, and in  summer same sort of pattern but  things are shifted further  northward.  If we look at Wisconsin, it  straddles the two trends, the  two sides. 

 Although we are on the wet side  of it so about a 5% to 10%  increase globally is what the  GCMs, the global models are  suggesting with somewhat higher  values in winter.  And in summer the models are  showing on average a slight  decreasing trend or a slight  drier climate in the summer.  But as I'll show next that  that's really a reflection of  the disagreement among climate  models more so than a  distinctive sign of what's to  come.  So now if we zoom in on  Wisconsin, this is work that  Dave Lorenz has put together  from CCR.  He's looked at 15 different  global models and looked at the  same time period, late 21st  century compared to the late  20th century.  And this time it's Wisconsin  only, so we're zooming in on  that northern American map.  The top panel is showing the  projected temperature change in  Fahrenheit for each month from  January over to December, for  each model represented by one of  these different colored lines,  and then the average among all  the models in the solid black.  And one point to take away from  this is that in every month and  in every model we're expecting  to get warming in Wisconsin on  average.  And that, unfortunately, right  now we see an awful lot of  scatter among the models.  So they're agreeing on the sign  of the change but not very well  on the magnitude. 

 And another take-home message  here is that there's really not  much of a difference between the  warming projected for winter and  that projected for summer.  So a slight increase in the  summer values but really pretty  steady throughout the year.  So now let's turn to  precipitation which is a more  difficult variable to stimulate  or project its future changes.  And here we see, again, a lot of  scatter among models.  However, we see that here's the  zero line, so no change.  We see that for three different  seasons, especially spring but  also winter and autumn, the  models are projecting a wetter  climate statewide.  In summer, on average, the  models are projecting a somewhat  drier climate.  But the real story is probably  in the spread among the models.  You see that some models are  predicting an increase in  precipitation in the summertime  and other models are projecting  quite a decrease.  And this is unfortunate of  course for agriculture because  they need to know what the sign  of the change will be, but at  this point we have a lot more  confidence in the projected  precipitation changes in other  seasons, especially spring, and  I'll be coming back to that  point later. 

 One thing that the climate  models are very confident about  is that we'll be seeing more  heavy rainfall events.  So it's possible that what we  saw last June is a harbinger of  what's to come.  And the best accepted  explanation for this is fairly  simple.  And that is if we pump more  greenhouse gases into the  atmosphere, which are heat  trapping, some of that energy  gets reradiated back to the  surface, land or ocean.  Warmer surfaces tend to  evaporate more.  More evaporation means more  moisture in the air on average  in a future warm climate.  And what that means is that when  the conditions are right for  heavy rainfall, say we get a big  thunderstorm complex or a slow  moving front, that the  atmosphere can better wring out  the greater availability of  moisture and produce a heavier  rainfall event.  So whereas in the recent past  maybe certain conditions would  have produced an inch rainfall  in a day, maybe in the future it  will be an inch and a half or  even two inches.  So that's the basic physical  understanding of why we think  there will be an increase in  heavy rainfall events in the  future, sort of the physics of  it.  And here's an example of more of  the statistics. 

 So this is a figure that came  out of the US Climate Change  Science Program last summer.  And these are globally averaged  values of projected changes in  precipitation intensity.  Let me walk you through this.  So it's showing how hard the  rain will fall, generally rain,  some could be snow, for  different categories of  precipitation intensity.  So over here on the left you see  say the 5% to 10% lightest  precipitation events daily at  different points in the world.  So this would be say less than a  tenth of an inch per day.  And then we see in the middle,  moderate precipitation amounts,  50th percentile.  And then over to the right these  are the 5% to 10% heaviest  precipitation days.  And what stands out is that we  see the models for three  different emission scenarios, so  a high polluting emission  scenario in blue, intermediate  in red and then in light yellow  a low optimistic greenhouse  emission scenario.  But all of them show the same  basic pattern, and that is that  the light precipitation events  should become somewhat lighter  in the future than they do  today. 

 And as we go further to the  right toward more and more heavy  events and the heavier the  further to the right, we get the  biggest increase in intensity.  So up to 10% and then 20% and  then 30%.  And by the time you get to the  5% of wettest days the models  are projecting increase in  intensity and magnitude of over  20% and getting up to close to  50%.  So this is a disturbing kind of  picture because it suggests that  floods, if all else is the same,  will probably become more  common.  We'll certainly have more fuel  for those floods and we saw in  the recent past what heavy  rainfall can do.  Another way of expressing this  is in what's called the return  period of heavy precipitation  events.  This figure is showing the  future return periods of modern  20-year heavy precipitation  events.  So that means at any point in  this map the precipitation that  occurs on average once every 20  years, so very rare, very heavy  events, the colors here are  showing how frequently they'll  occur according to model  projections by the late 21st  century.  So let me walk you through this  one.  The blue areas are 20 years. 

 So there's some places that show  no change.  So the 20-year event at present  is the 20-year event in the  future.  But many places on this map are  orange and even red including  Wisconsin right here.  And if you translate that color  down to the color scale that  represents about five years.  So that means the once in  20-year type of event that we  get in the recent past in the  late 20th century would happen,  according to the model  projections, once every five  years on average.  So that would be a tremendous  change and have big implications  in terms of infrastructure,  building bridges, building dams,  building culverts and so on and  health impacts as Jonathan will  talk about next.  This is a curious figure.  This is one that didn't copy  over well.  But I'll run you through it.  It's not even a Mac to PC  problem; I'm not sure what  happened. 

 But basically one of the panels  is showing that these changes in  North American heavy rainfall  events happen globally.  So this is not just unique to  Wisconsin, it's not just unique  to North America, but the models  are suggesting that almost  everywhere, at least on land,  should be seeing an increase in  precipitation intensity.  And at the same time, conversely  and kind of ironically, we're  expecting to see more dry days  as well.  So this suggests a future of  more droughts and more floods if  the models are correct.  So you can think of this as sort  of a shift, if you live around  here, toward our springtime  precipitation pattern toward  more of a summertime.  So in the springtime we get lots  of rain, lots of days with rain,  but not really, really heavy  rains usually.  In the summer we don't get as  many rainy days around here, but  when the rain falls it can fall  really hard.  And that's more or less the  pattern that were expecting in  the future.  And then the ghost image on the  right here is showing, or would  be showing, the increase in heat  waves.  And it's showing that everywhere  in the world, no exceptions, not  even Antarctica, is immune from  an increase in heat waves  relative to the variability that  exists at present day. 

 And I think Jonathan is going to  be addressing the health impacts  of increased heat waves in his  talk.  So what I've shown up to now are  the results from global climate  models.  And they're really useful  because they allow the whole  climate system to interact in a  very cohesive, self-consistent  way.  But they're limited if we want  to look at impacts on a regional  scale or a local scale like  Wisconsin because they represent  an area of Wisconsin in a very  crude way.  So these are grid boxes in a  climate model.  They represent, for a single  point, uniform conditions as the  climate model sees them for  temperature or precipitation.  And that's not so good because  we know that the climate of Eau  Claire is not quite the same as  the climate of La Crosse or the  climate of Madison.  And so what we want to do is  translate these broad-scale,  coarse, global results  projections onto a finer scale,  and at the same time try to  correct for some of the inherent  model biases that exist in the  global models.  And so this is a technique  called statistical downscaling  and de-biasing, and it's one of  the central thrusts of the  Wisconsin Initiative on Climate  Change Impacts, WICCI, and  people in CCR, especially Dave  Lorenz and Michael Notaro, have  been working on doing this.  And this figure is a schematic  showing the point of statistical  downscaling. 

 So you can think of a climate  model that might resolve things  at one or two degrees resolution  latitude/longitude, and what we  want to do is to translate or  tailor that information on to a  very fine scale of Wisconsin  that will take into account the  fact that there are lakes nearby  and we get lake effect  influences and the fact that the  topography is not uniform in  Wisconsin, it's higher in the  north than the south.  And so this is a technique that  can be very powerful if done  correctly and can give  policymakers and impacts  assessment folks much better  data to work with.  And so this is just being worked  on now.  We've completed the initial  results.  We don't have things finalized,  but I do want to show some  initial results tonight in terms  of extreme events because I  think it's important that we get  the word out at least to whet  your appetite for what's to  follow.  We're going to be releasing this  publicly in the next few months,  but this gives you an idea of  some of the things that will  come out of this, and it's  actually quite encouraging the  way the initial results are  looking.  So these are downscale climate  model projections for extreme  temperatures in Wisconsin that  Mike put together.  On the top are the average  number of very cold nights per  year for the late 20th century.  The middle panel is the same for  the late 21st century, and the  bottom is the change in these  zero degree nights.  So one thing that's encouraging  is that we're certainly seeing  in the recent past this  north/south gradient. 

 So a lot more very cold nights  in northern Wisconsin than the  south.  But you also detect a lake  influence.  So along lake Michigan you see  that the statistical downscaling  is picking up the fact that the  lake has a moderating affect on  very cold nights, and you even  see it up here if you look  carefully around Lake Superior.  Even a cold lake like that helps  to moderate the climate.  And so you see it also for the  late 21st century, but I want to  focus on the change in these  very cold nights and the climate  models, the downscale results,  are suggesting that everywhere  on this map we'll see a decrease  in the number of very cold  nights.  On average about two weeks fewer  in Wisconsin and 10 fewer in  Madison.  If we look now at the  corresponding extremes for heat,  90-degree days, we also see a  lake influence.  For instance, Door County has  fewer very hot days than  locations just to its west.  That's encouraging.  We see the same sort of lake  influence for the late 21st  century. 

 And, unfortunately, if you don't  like hot weather like me, we see  a pronounced increase in the  number of very hot days.  And it's similar in magnitude to  the very cold nights in terms of  the change.  So the models are suggesting  about 17 more very hot days,  90-degree days, in Wisconsin and  three weeks or more in Madison.  So you notice that the change,  at least for our area, the  models are suggesting that the  change in extreme heat, 21 or  more days of 90, is greater than  the change of very cold nights  of 10 days fewer.  If we look at the same thing in  terms of extreme precipitation,  1-inch events, and I'll show  2-inch daily events and 3-inch  events, we see also some  realistic features from the  models.  First of all the number of  1-inch days per year in the late  20th century is about six per  year, which is right on the  mark.  We see more of these in southern  Wisconsin than in northern and  in the UP, which is also  realistic.  You see this red area, the  highest values, creeping larger  and further northward in the  late 21st century, and that's  reflected here in the bottom  figure which is now the  percentage change, rather than  absolute change, in the number  of days greater than 1-inch  precipitation amounts.  Statewide the models are  suggesting a 10% increase, and  the highest percentage changes  are occurring in the north where  these events are less frequent  than they are in the south, but  you see that almost everywhere  is showing some amount of  increase at least greater than  zero.  Now if we look at the same thing  in terms of 2-inch events, we  see that the color scheme is the  same, the color scale is the  same for each of these, but  notice that the numbers are  different. 

 So now 2-inch events are  occurring only typically about  one time per year, but they also  occur more frequently in the  south than the north, which is  realistic.  And if we look at the change we  see that the projected change is  somewhat greater than that for  the moderate extreme of one inch  per day, 17% increase statewide,  some places now greater than  30%, especially up in the UP and  northern Wisconsin, but there  are also a few areas in green  that are projected to have  slight decreases.  And that will be become even  more apparent in the next  figure, 3-inch days, which are  very uncommon.  Fortunately, at present, less  than one time per year.  And they become typically more  common in the future according  to the models.  25% increase statewide.  Some areas now 60% or greater,  this color scale has changed  again, or the scaling.  But notice again that there are  some areas of green, some  swatches in green which  indicates that the models are  suggesting that some regions  will actually see fewer even  though the statewide average is  greater.  And that's an important feature  of assessing extreme events  because 3-inch rainfalls are so  unusual that there's an element  of randomness in them.  Even if we didn't have a climate  change you wouldn't expect to  see the exact same number from  one 20-year period to the next. 

 And this is a challenge in  assessing extreme events, and in  terms of climate change because  we always have that overprint of  randomness.  And so this is one of the real  challenges in trying to figure  out how extremes will change in  Wisconsin or anywhere as the  climate changes.  So as I said those are hot off  the computer.  We haven't had time to study  them in great detail.  You'll be hearing more about  those in the future, and  hopefully in the next few  months.  But one project that I've had a  chance to work a bit more on is  from Chicago which is fairly  representative of the climate of  southeast Wisconsin.  These are downscale  precipitation projections for  that region.  And this figure is showing a  comparison of these downscale  precipitation changes for the  late 21st century for Chicago  for mean precipitation, on the  left, and for extreme  precipitation, the wettest 5% of  all days on the right.  Showing here for different  seasons winter, spring, summer,  autumn and annual.  And the bars represent two  different global climate models  whose results were downscaled,  the PCM model and the GFDL  model, and for two different  greenhouse gas emission  scenarios. 

 The high end, A1, and a lower  end, B1.  But the point of this figure is  to show you that there's a  strong suggestion that the  changes in extreme precipitation  follow closely with those of  changes in the mean  precipitation.  If you pick, say, winter, you  see that both climate models,  both emission scenarios, show a  sizable increase in mean  precipitation of about 20% in  Chicago.  And they're both showing  increases in extreme  precipitation during that season  as well.  Spring stands out the most,  that's why I've highlighted it  with these arrows.  Increases of about 40% in the  mean and increases of even  slightly higher than that in  extremes but the magnitudes are  similar.  Likewise, in summer one of the  models produces a sizable  increase in mean precipitation,   also extreme precipitation.  The other climate model predicts  that there will be a drying  climate around Chicago in the  mean and also in the extremes.  So you can go and just eyeball  these and see that there's a  good match between the means and  the extremes.  And the reason that's  interesting and important,  potentially, is that it's  harder, I think, to get a handle  on why the extremes change. 

 Physically why they change.  We have a better chance of  understanding why the mean  climate changes.  And if the two track each other  very closely then hopefully we  can understand, get some good  physical understanding of the  changes in the extremes by  understanding the changes in the  mean.  And let me give you an example  of that.  This is now the projected spring  precipitation changes from a  collection of 20 different  global models for eastern North  America.  Don't worry about the magnitude  of these numbers here, the point  is that areas in the green are  supposed to get wetter in  the spring by the end of this  century and areas in yellow and  orange are supposed to get  drier.  If you're a climatologist you'd  get excited about this because  this is showing a very coherent  kind of pattern.  This isn't just one point here  and there.  This is saying that the whole  Great Lakes area and beyond  should get wetter in the spring  at the same time the Gulf area  gets drier.  And probably the reason for that  is that the climate models are  projecting that the circulation  of the atmosphere should change  such that we have more low  pressure to our northwest,  higher pressure over the  Atlantic and that sets up a  flow, the counterclockwise flow  around the low, the clockwise  flow around the high, to draw up  more moisture, more southerly  winds from the Gulf of Mexico,  transport that moist air into  the Great Lakes where it then  gets rained out as greater  precipitation. 

 And so this is probably a good  explanation for the increase in  mean precipitation and quite  likely extreme precipitation too  that I just showed in the  previous slide.  So these are the sorts of things  that you can do when you have  believable climate data and you  have a group of people who are  studying them to understand,  produce some sort of assessment  of what these results really  mean for impacts.  And before I lose my voice I'll  get to the conclusions.  The take-home points from this  first half of the lecture  tonight.  Significant warming is expected  in Wisconsin during all seasons.  We're looking for a wetter  climate generally but especially  during winter and spring.  Summer changes are still  uncertain.  In terms of extremes, the models  are suggesting a shift toward  more heavy precipitation events  and also more droughts not only  around Wisconsin but in much of  the world.  We can look for more frequent  and intense heat waves but also  less severe cold.  At least in Chicago the model  changes in mean and  precipitation are very similar. 

 So if we can understand why the  mean climate changes, maybe we  can understand why the extremes  are changing.  The observed trends to date are  showing more heavy precipitation  around Madison, at least in the  past decade.  Across Wisconsin they're showing  less extreme cold, but curiously  little change in extreme heat.  And then finally, and this is a  lead-in to Jonathan's talk,  there are all sorts of likely  impacts from these.  You can use your imagination for  some of them.  Infrastructure, I've alluded to,  especially in terms of the  increased heavy rainfall events.  Agriculture, likewise, farm  fields under water we saw last  summer.  And then finally human health  and I won't steal the thunder  from Jonathan.  I know he's going to talk about  how human health is affected by  extremes of both precipitation  and heat as well.  So I will wrap up there, and I  think the format is that I'll  take questions now from my  portion and then I'll turn  things over to Jonathan. 

 (applause)