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0:15
Well hello. It's a little early, so we don't have a full crowd yet. But we're off to a good start. The way we visualized this program, yesterday's wonderful lecture by Michael Mann and today's, is what, Michael set the stage yesterday in a big way, is we know what the problem is. The question is, what can we do about it? And today is meant to be a bunch of talks dealing with how can we respond. One of them what are the ways in which
0:45
we can mitigate the increase in global gases in the future there's a wonderful book called drawdown I don't know how many of you know this book written by Paul Hawken not what written by him but organized by him it's a New York Times bestseller it's a beautiful book it can actually tells us and it was put together by a large group of people it's about 80 or hundred people who contributed this they a whole set of things that we can do and an estimate a
1:17
realistic estimates if how much this would these each one of these things that we were able to implement them could cause a reduction in the carbon dioxide of the atmosphere between now and 2050 these are things that could actually be done the first one on the list you'd be surprised to know is to educate women and girls in developing nations that doesn't sound like a way to treat global warming but bassy basically reducing the size of the populations so
1:45
that we don't have that population pressure in the distant future major thing Agra regenerative agriculture which will hear about today from Professor Lau these are things we're gonna Hawks talk about those all day to day and I think that you'll find some of these things very interesting people have to come up with ideas and you can all be part of it in your own way well and I hope that at the end of the day we'll have a reception with an open mic
2:11
if you have any ideas and thoughts that you'd like to talk about any any things that you'd like to contribute come there prepare to say a few words about it and we to have you talk thank you and now I'm gonna turn over the program to our master of ceremonies for the day Patti Jones good morning everybody and thank you for being here it's my pleasure to be the emcee for this event in which I will be introducing all of our speakers also just so you know I will keep us on time and as you can see
2:55
from the program every speaker has a generous hour for a presentation and some of them might take most of the hour and some of them are gonna end early and so they'll be probably a good look at a lot of time for questions and answer with the audience so our first speaker as you can see here is Jim hurl he is the Scott presidential chair of environmental science and engineering at Colorado State University he's the former director of the National Center
3:17
for Atmospheric Research NCAR where he was also a senior scientist in the climate and global dynamics laboratory his PhD in atmospheric sciences is from Purdue he's also the former chief scientist of the community climate projects in G and CJD which includes a community Earth System model and a former director of the CDG and ncar earth systems laboratory his research is centered on empirical and model modeling studies and diagnostic
3:44
analyses to better understand climate climate variability and climate change he's co-authored or authored more than a hundred peer-reviewed journal articles and book chapters as well as a dozens of other planning documents workshop papers editorials he's edited several books and has been acknowledged as a highly cited researcher by Thomson ISI and of course he's given many professional invited keynote talks so please join me in welcoming to the stage Jim hurl
4:13
thank you very much well good morning everyone and thank you for coming so bright and early I know students don't like 8:00 a.m. classes and I know faculty don't like 8:00 a.m. classes so appreciate those of you that are here today it's a real pleasure to be here and I'd like to just begin by echoing a few of the comments that's already been made I'd really like to thank the organizing committee for putting together I think this very important and
4:44
very timely symposium on the topic of confronting the challenges of climate change I'd also too like to thank Patti as the main point of contact for all of us coming in she was just absolutely wonderful to work with and answer questions and if this talk doesn't hit the mark I'll blame her because she said she thought this talk looked great so see and I'd also like to congratulate Ted Brown it's my first opportunity to to meet professor Brown and I'd like to thank you for all of the work that you
5:21
have done the awareness and the attention that you're raising to this particular issue the books you've written on the topic and it's real honor to meet you and happy birthday and yesterday I had the opportunity to sing happy birthday as part of the group and I can assure you I'm not going to do a solo now so that's that's a very good thing and then finally I just like to acknowledge the talk to my my colleague in my friend Mike man gave yesterday
5:49
fantastic talk I was sitting in the audience thinking why did I ever agree to talk about climate change science after Mike he's a fantastic communicator but I know he really enjoyed giving me the annual interdisciplinary lecture here and did a fantastic job so let me try to take you through a few of the points that I want to make and explain the rationale for the presentation I did put together this is a slide and I'll talk about the source of this slide in
6:19
just a few moments but this is a very simple depiction of the observed changes across the globe in surface temperature over the last several decades relative to the first part of the 20th century and as you can see from this figure there's a lot of red colors the red denote a warming in terms of this epic difference if you fit something like a linear trendline and average temperatures everywhere across the globe there's been a warming of
6:53
about a degree Celsius or 1.8 degrees Fahrenheit since about 1900 and this is the very significant global warming that Mike spoke of yesterday my own research in in looking at climate variability and the mechanisms that produce climate variability are interested in things like this you can see that even though the globe has experienced very significant warming over the last century and really since the pre-industrial times that warming is
7:29
not spatially uniform there are marked regional variations there are seasonal variations the two blue circles denote a couple of areas of the globe where the warming has not been very pronounced although in recent years warming has been evident in these regions as well and likewise you can see other parts of this map where the warming is is even greater than what the global average is and that is because as Mike described yesterday there is no scientific debate
8:05
around the fact that anthropogenic climate change is occurring but of course the climate system also varies due to natural processes El Nino events other modes of coupled ocean atmosphere variability and even though natural variability does not really have a fingerprint when we average globally and look at global trends over this time period the natural variability of the system is very important regionally and locally and of course there's many stakeholders there's many decision-makers who are
8:43
trying to understand how to confront the challenges of climate change and it's a very important component of the problem to understand the role of natural variability in climate predictions and climate projections over the coming decades and also how anthropogenic climate change influences and maybe modifies some of these so-called natural patterns of climate variability and Mike touched on that a little bit yesterday when he was talking about the jet stream
9:13
so that's that's what I was originally thinking of talking about focusing on is our ability to understand and predict maybe on decadal or multi decadal time skills these natural variations in climate and how that fits in to the bigger picture of anthropogenic climate change but in looking at the agenda and realizing that Mike was giving this great lecture yesterday but not knowing how many people attended that I've decided to try to set the stage a bit
9:45
myself for the remaining talks today so I'm going to go over some of the materials that might present it yesterday and reinforce some of those ideas in response to a question Mike made the point to one of the things we can do is all talk about climate change and so I spend a lot of my time a lot of my career has been spent communicating climate change science as well and as I was discussing with Mike yesterday before his talk we all tell that story
10:14
in slightly different ways so my hope is that perhaps some of the slides that I'll show on some of the points I will make can give you some tools and reinforce some ideas as you talk about this problem because I think it is very important that we talk with many diverse groups and many diverse stakeholders about indeed the challenges in the imperative that we we confront climate change moving forward so to do that I'm going to give kind of a brief overview
10:46
move through this relatively quickly and I wanted to call out this climate science special report as part of the fourth national u.s. Climate Assessment that was just released about a year ago and I'll be referring to many figures from this report this report is available on the web it's very readable there's a very nice executive summary and if you want to look at some very nice figures and graphs and depictions of what we know about climate change
11:19
science this is really a wonderful resource and it also gives me the opportunity to acknowledge Dom weevils who is here raise your hand professor a good friend of mine in the Department of atmospheric science here at Illinois and Don has done a remarkable service in his career in terms of his own personal research contributions but really playing community leadership roles such as being the lead author on this US National Climate Assessment so if you have detailed questions on anything I show
11:52
you can ask done so yeah you're welcome Don one of the things that I like to try to communicate is I can stand here and I can go through graphs and figures and things that I will but but often again going back to this concept of discussing climate change it's a lot to remember especially for non-experts on the topic and another colleague Tony lazerwitz at Yale University came up with his summary of climate change in 10 works and I really like this slide because when I
12:32
talked to the public I really like to try to convey if you can remember these words you can really have a meaningful conversation about climate change the first point is that it's here this is not something that's going to happen in the future Mike talked extensively yesterday about the impacts that we are seeing across the globe especially when it comes to changes in extreme events so this isn't a future problem is here causing problems now it's us there's no
13:02
scientific debate there's no credible scientific debate through the burning of fossil fuels and changes in land use we are increasing concentrations of greenhouse gases in the atmosphere and the climate system must respond to that and we can show that the growth of carbon in the atmosphere is due to human activities is serious okay the impacts that is already having the impacts that are going to grow as we move into the future are very serious
13:35
this is a problem we really do need to pay attention to and come up with mitigation as well as Abnett tips adaptation we have to adapt but serious debates and discussions about mitigation approaches are required at this point again scientists agree that climate change is real and I think a very important component of the message especially when you talk to the public is don't just give kind of a gloomy look at all this is happening this is an
14:04
enormous problem there are solutions and I could not agree more strongly and with Mike and his statement at the end about these are the things we should be debating having honest policy debates about how to solve this problem but it is solvable if 10 wars is too many I have a colleague at CSU that does it in six or even three if you take the word off this is simple that's his word I kind of prefer straightforward as Mike said yesterday it's serious and a
14:39
solvable the main things in terms of the scientific consensus I just like to point out that and the formatting of the slide is a little messed up here I apologize for that but you know it's not just Mike it's not me it's not dawn it's not just climate change scientists talking about this we do have things like the US National Academy of Sciences that was with providing independent objective advice to policymakers and oh boy I'm
15:14
sorry the formatting the the MACT of Windows transition I guess but the key point here is really that our own National Academy highlights that the scientific understanding of climate change is sufficiently clear to justify taking steps to reduce the amount of greenhouse gases in the atmosphere and you can see that internationally all of the national science academies agree on the scientific consensus around human caused climate change in the importance
15:43
of dealing with the problem as do professional societies the American Geophysical Union triple-a us American Association for the Advancement of science all professional science academies or groups have similar statements and then of course there's the IPCC the Intergovernmental Panel on Climate Change this was raised yesterday as well that is a body of scientists from around the world that are convened under the United Nations environmental programme and the World Meteorological Association
16:18
to provide policymakers not be policy prescriptive that give them a true assessment of our understanding of the problem and in the fifth assessment report the conclusion was that climate change is unequivocal and remember Mike talking about because of this process because of this international body and everyone must agree on the report language it tends to be conservative scientists are conservative by nature we want to test and retest and make sure
16:50
that we don't make claims that can't be 100% backed up but climate change is unequivocal and unprecedented what we're witnessing now especially in terms of the rate of change and that again the impacts are very widespread I also like to emphasize that it's not a new topic we have been studying aspects of climate change for a couple of centuries now this is one of the scientists this is John Tyndall who is a physicist we spent his career in part understanding
17:27
infrared properties physical properties of the atmosphere and in in the 1860s he was measuring in laboratory experience experiments what gases absorb thermal radiation and was documenting that water vapor and carbon dioxide are major absorbers and then our Haney Asst who was also a physicist but better known for being a chemist one of the founders of modern the modern science of physical chemistry went on and he won a Nobel Prize actually for chemistry in 1903 and
18:05
was the director of the Nobel Institute from nineteen 505 on until his death but a really seminal paper that is often cited in my community is that in 1896 he was very interested in glacial cycles and he noted in 1896 the carbon dioxide will be building up in the atmosphere due to industry he calculated the earth would warm by about 4 degrees for a doubling which is roughly the number we still have today in 1896 and also recognized since he was very interested
18:43
in the Arctic regions and the onset of glacial cycles that the warming would be greatest in the Arctic through the amplification factors in the Arctic as the sea ice melts the ocean absorbs more solar radiation there's a positive feedback effect really really remarkable paper it's really humbling as I've gone through my career I've really appreciated the work of the scientists that have come before us and and too often this work is really not fully
19:12
appreciated and then David Keeling who was a oceanographer at Scripps Institute of Oceanography and began to measure carbon dioxide directly back in 1958 and really alerted the world to the potential risks associated with rising carbon dioxide levels that carbon ducts an Illinois graduate I was coming to that Don but thanks now we're even so but this curve is so iconic that is simply referred to as the Keeling curve the measurements are taken at Mauna Loa
19:54
on the Big Island of Hawaii and I had the opportunity to to visit this site just a few months ago and I also like to point out that the rising levels that are noted by this curve we're actually noted in a report in President Johnson's administration talking about the dangers of increasing concentrations so the point is it's not a new topic and this is the the Keeling curve that Mike showed yesterday you can see that clear rise since 1958 in global
20:24
measurements of co2 well point measurements that is well mixed globally and today we're somewhere in the neighborhood of about 409 or 410 parts per million by volume in terms of co2 so if you'll bear with me oh yeah this will work I wanted to show in trying to make this point the climate change is not a new topic we can talk about Fourier and in Tyndall and our Haney US and the like but this is a little movie clip I really like to show if you'll bear with me it
20:59
comes from a TV series that was aired in the United States in the 1950s GE Science hour and the producer of this film was Frank Capra I think we all know of Frank Capra won three Oscars for Best Director and nominated for two others including us a wonderful life he was a pretty conservative fellow he strongly opposed FDR a big proponent for American individualism that he was also a scientist had scientific training and he really valued that role this particular
21:37
clip is taken from an episode of the science hour where they talked about the weather and what the weather is all about but they also talk about climate change and the risk that opposes so I'm going to start this and hopefully the volume works I'm trusting that but 1958 on American television no volume can we get volume what what would happen if we could change the course of the Gulf Stream or the other great ocean currents or warm up Hudson Bay with atomic furnaces extremely dangerous questions
22:32
because with our present knowledge we have no idea what would happen even now man may be unwittingly changing the world's climate through the waste products of his civilization due to our release through factories and automobiles every year of more than 6 billion tons of carbon dioxide which helps air absorb heat from the Sun our atmosphere seems to be getting warmer this is bad well it's been calculated a few degrees rise in the earth's temperature would melt the polar ice caps
23:10
and if this happens an inland sea would fill a good portion of the Mississippi Valley tourists and glass-bottom boats would be viewing the drowned towers of Miami through 150 feet of tropical water foreign weather we're not only dealing with forces of a far greater variety than even the atomic physicist encounters but with life itself so again 1958 and I really like to emphasize this Mike talked a little bit about some of the unfortunate some of
23:43
the political nature of the climate change science debate one of the things that we often have to respond to is this is something that we've sort of created so that Donna and I can get more funding for a research and I would really like to show these kind of clips to the public so some basics I know this is a diverse audience but I understand I know that you know the basics I'm not gonna spend time on this the greenhouse effect you know that what powers with powers
24:09
life on Earth what powers the weather and the climate systems the solar energy that passes through the atmosphere much of it is observed at absorbed at the surface of the earth the earth re-radiates that as infrared radiation and then it's the greenhouse gases in the atmosphere that capture that infrared radiation and re-emitted in all directions including back down toward the surface and of course the greenhouse effect is a good thing it allows us to
24:38
live on this incredible planet it's just the right natural balance the greenhouse effect on the planet Earth we can think about Mars which has an atmosphere made of co2 but the very little methane very little water vapor not enough to really reinforce the greenhouse effect so the planet of the surface of Mars is largely frozen in contrast Venus which also has an atmosphere with co2 levels about 300 times that found on the planet Earth has produced a runaway greenhouse effect so
25:11
that the surface of Venus is warm enough to to melt lead so the greenhouse effect is just right water vapor is the key absorber but the build-up of co2 we that we're changing the system and that's the problem we're increasing greenhouse gases very rapidly we know this is due to human activities the rate of change greatly exceeds anything that we've seen in nature and that simply means the more heat is being trapped in the system this gets back to the
25:43
understanding and the argument is fairly simple fairly straightforward it's not a question about whether or not we'll see consequences of this the questions the scientific questions are precisely how we're at what rate the earth will be responding to this increase in greenhouse gases this is another figure that I really like to show it puts it in historical context paleo climatology we can analyze the air bubbles that are trapped in ice cores and again
26:17
remembering co2 there's a very well mixed gas globally and this shows if you will the natural variability to the system these minima around 180 parts per million by volume represent atmospheric co2 concentrations during the ice ages when ice a metre thick build up over many of the continental areas and the peak here in these interglacial warm periods is around 280 parts per million by volume what I like to point out is that due to these natural variations
26:52
which relate to variations in Sun Earth's orbital geometry and takes some time to move from these cycles from about a hundred and eighty up to 280 parts per million by volume about 15,000 years or so roughly speaking and these are sort of the natural levels of co2 at least over the relatively recent past of Earth's history where are we today again we're at about 400 it's this rate of increase we've we've made this increase over a very very short period of time
27:28
relative to the geologic record and this is where we're headed this is where we're headed if we continue to emit greenhouse gases at the rate that we're currently emitting them to me this is a very scary graph this really puts into perspective how far outside the range of natural variability we are how we are conducting an experiment with this planet that has never been conducted before greenhouse gas concentration co2 have been very high in the atmosphere before on very long timescales tens of
28:07
millions of years that it was a very different planet this is the anthropogenic perturbation on these natural cycles so what are some of the symptoms I'll go through this very quickly as as I said it's not a question about whether or not the planet will respond it's exactly the nature that responds more heat is being trapped in the system so one of the effects of that is the warming of surface temperatures around the globe this is very similar to
28:34
that first plot that I showed this is just looking at the change in temperature since 1950 when we have more global observations and you can see that the warming of the planet is evident nearly everywhere over this period we can average all of these temperatures together across the globe and produce these kind of plots that you've often seen before this is just the evolution of annual global surface temperatures since 1880
29:04
these are anomalies so relative to the average from 1901 to 1960 if you just remove that average from the individual annual means the blue bars indicate where global temperatures were cooler than this average the red where it's warmer and you can see a very clear upward trend if you if you look at the details of this plot like I've said about one degree of warming since 1901 you can really see how rapid the increase in global surface temperatures
29:35
has been over the last several decades since about 1979 or so 2016 is the warmest year on record you can see the second third and fourth warmest years there it turns out that 17 of 18 years in the warmest record have occurred since 2000 the exception being 1998 when there was a very large and significant El Nino event a natural variability that also contributed to the warming of the planet in 1998 the coldest year in the 21st
30:09
century is 2008 in 2008 it's the coldest year in this century but it's warmer than all years prior to the 20th century in this record of global surface temperatures you can average the data even further and look at decadal averages and when you do this in terms of surface temperature you can see very clearly this this this indication of a warming planet we can look at the US this is the plot of temperature change over the US again it's about a Celsius
30:45
of warming since about 1900 when averaged over the United States but now when you start to look on regional scales you can see more heterogeneity more details in this pattern including a relatively lack of warming over the Southeast United States and there's a lot of studies trying to understand that but even in recent years this region of the US about 95 percent of the of the land area of the US has experienced warming over the last century and we
31:17
often talked about temperature wherever we put thermometers if we put thermometers in the oceans on the surface if we take measurements from balloons or from satellites looking down from space we see that the planet is warming we see many other independent measures that are physically consistent with the indications of a warming world and many of those are listed here on this slide that we could talk about and when we think about the future the
31:46
extended outlook business-as-usual if we keep going about things the way we are it's going to become much warmer and the impacts are going to become much more pronounced this is a plot that that Mike showed yesterday I think it's very important to we can think about changes and when you talk to the pulp book public and you talk about a degree and a half of a warming it doesn't sound like much but where that impact really
32:17
comes in is when you shift this this Gaussian distribution this bell curve to the right you can see the very significant changes that occur in the so-called extreme events so if you just think about this as temperature and you assume there's no change in the shape of the bell curve no change in the variability just a shift in the mean even if that was all that was happening in in a new climate what we used to think of this very cold weather or cold
32:43
extremes occur much less frequently and the very cold extreme temperatures we witness will no longer occur conversely what we used to think of as record heat now occurs much more commonly and we set new records in terms of extreme temperatures which then has implications for droughts and heat waves and wildfires and impacts on human health and the like and and we can see this when we look at the data so this is a plot looking at surface temperatures
33:18
over the northern hemisphere again average over this period from 1951 through 1980 you can see this very nice sort of Gaussian distribution you have an average you have the climate system is variable and weather is variable and we have cold spells and we have warm spells but if you can begin to just march through the decades this is 1981 through 1991 this distribution is indicated by the Green Line you can see in the data this shift
33:47
in the extremes which is a very nice simple plot to show this is what we are witnessing Mike referred yesterday to the European heat wave and there's many many many other examples we can give of changes in extremes this is a plot that I often show one of the nice things about looking at anomalies over Europe is there's very long instrumental records actually go back to before 1800 but this is looking at 1850 up through several
34:18
years ago this is the heatwave in 2003 and as a climate scientist Don and I get a phone call and what the media often wants to know whether it's this heatwave whether it's hurricane Michael any number of offenses the question is you know Jim is is this because of global warming or is it due to the natural variability that system what's going on and I think the important point to communicate is those really aren't the right questions climate change is
34:46
occurring ok natural variability is occurring with this background of climate change so it's a combination of the two and this slide illustrates that the very rich natural variability of the climate system causes these these changes from one summer to the next in this particular measure some temperature some summers are cooler than average some summers are warmer than average that's the natural variability of the system roughly speaking that same
35:14
magnitude of variability is still continuing but now it's imposed upon this upward trend which means it's much more likely that we're gonna see record-setting events such as this heatwave as was also described yesterday and I think it's important point to communicate when we think about this there may be things that are confusing for the public at at at first look wait a minute climate scientists are saying the planet is warming so I kind of get
35:45
it that it's gonna be hotter we're gonna have more heat waves we're gonna have maybe more droughts or wildfires but how can it be producing all this flooding as well and again it's relatively simple over the oceans more water evaporates into the atmosphere as Mike showed yesterday a warmer atmosphere holds more moisture so when it rains even if the dynamics of the system don't change at all when it rains on average it's gonna rain more it's gonna rain harder that's
36:14
going to lead to more flooding events likewise over dry regions or semi-arid regions the little bit of moisture that's in the ground it's going to be evaporated out the rest of the energy just goes in warming the surface and this leads to more pronounced heat waves and droughts I'm gonna show one other movie this is produced at the institution as Patti said I was part of for the first twenty eight years of my career in the National
36:41
Center for Atmospheric Research this is a very kind of light-hearted but nice cartoon that illustrates what we're seeing and why we're seeing it and it has to do with baseball so I don't know if there's baseball fans out here Cardinals and Cubs fans I know I'm a long suffering Reds fan so my seasons been over but here we go what do steroids in baseball have in common with climate change well imagine a baseball player who's been taking
37:10
steroids this Paypal player steps to the plate and it's home run and yes the question was at home run due to the steroids if you look at the number of home runs he hits over a season when he's taking steroids and compare that to a previous season when he wasn't taking steroids it is only then you can figure out but the steroids have made him more able to get on run because it's made him stronger and the chances of omitting home run are greater so by adding just a
37:36
little bit more to his naturally occurring steroids in the human body we changed the background base state of our systems ok got it but a lot of bad things happen when you take steroids right the greenhouse gases that we're adding to the atmosphere from the burning of fossil fuels are the steroids of the climate system the atmosphere is very small amounts of greenhouse gases that occur naturally so by adding just a little bit more of those greenhouse
38:01
gases by the burning of fossil fuels to the air we change the background state of the climate system we increase the temperatures just a little bit but that increase of temperatures is enough to shift the odds toward a much greater chance for extreme heat events and extreme precipitation events normally you'd expect record lows and record highs to balance that over time but now we're getting almost three record highs for every record low so just as a
38:28
baseball player on steroids can occasionally strike out climate system with increased greenhouse gasses can still experience record cold temperatures but the chances of record high temperatures are still much greater and that's what steroids in baseball have to do with climate change to find out more about climate change and extreme weather check out you cart got edu slash Atmos News okay so I think that those again I know this is a very
39:01
accomplished audience you know there's but there's a wide background of people and again this is all in the spirit of the importance of communicating this communicating it to our colleagues communicating to the public and for me these kind of tools really help I'm not going to go into detail on this this is really speaking to the fact and I've mentioned several of these already there's a lot of impacts these impacts are going to be growing worse and more
39:27
pronounced as we move into the future adaptation mitigation strategies I'm really looking forward to some of the talks that follow today beginning to indeed discuss how we confront this challenge that's not my particular area of expertise but it's but it's critically important we have to adapt we are committed to a certain level of climate change you can think of it such as the oceans the oceans are warming as a result those oceans aren't going to cool down even if we reduce emissions down to
39:58
zero emissions that warming is going to continue on the timescale of centuries so climate change is occurring it's going to continue to occur we're going to have to adapt to that but we can really have this debate in this discussion around mitigation options and the best way forward for our planet at the risk of over playing my card of showing movies I'm going to show one last movie then I'm going to begin what I wanted to talk about originally but
40:27
that's going to be just a few minutes toilets in the smart grid this is a film that was done by a professor at Penn State another colleague of Mike Mane's his name is Richard alley and it's really trying to illustrate that there are strategies to solve this problem and we've been confronted with other challenges in the past it seemed insurmountable but we've been able to handle those challenges so let me just show this one last movie and then I'll
41:00
start to wrap things up so the earth provides lots of choices for clean low-carbon energy we can do big things to get benefits that none of us would ever walk away from so I think that's just a beautiful narrative and a short film that really conveys when you talk about climate change that we can come up with solutions to this problem I think that's very very important to convey and any talks on this topic so I appreciate you putting up again with a bit of a
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background I hope that helps set the context for the day now my daughter who's here in the audience Rachel her role Rachel raise your hand there you go she was giving me a hard time that she's heard me give that talk several times so I had to put a few new slides in for Rachel and if you can bear with me this is just touching very briefly because I got 10 minutes or so very briefly on some of my own work and I do want to convey it goes back to this point that
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anthropogenic climate change is occurring it's a very serious problem we have to figure out how to deal with this problem but when you talk with decision makers with various stakeholders with water managers with people in the agricultural sciences and whatnot you know the climate system is extremely complex and climate variability due to natural factors is continuing to occur anthropogenic climate change doesn't mean that becomes the only game in town
42:31
so if we're seeing trends in certain areas what's the likelihood that these trends might reverse even though the planet in general is warming and say drying in my part of the world in Colorado what does it mean if we have multiple summers or even a decade or two of wetter than average conditions now in the public discourse often that's twisted into see I told you there's nothing about this climate change thing but scientifically it's a very rich problem and I think it's very important as I
43:02
talked with those kind of stakeholders to explain what we're witnessing in the climate system and why so my own interest is very much what are the mechanisms of natural variability and what is the predictability of the system on those longer timescales we often talk about the inherent limit of predictability for the atmosphere is maybe only out to about 10 days or so weather forecasts are really very skillful out to that time but what can
43:27
we really say what can we tell society about what to expect over the next decade or maybe two decades and we know the climate system is very rich with variability on these timescales can we actually predict that and that's what I'm very interested in in terms of my own personal research and this is just you know kind of going back to this figure when you when you think about this pattern of temperature change relatively cool for instance over the
43:53
Northwest Atlantic warm or the northern hemisphere land masses this is very clearly tied to changes that we've seen in the circulation of the atmosphere over this time period this is a plot that shows the difference in sea level pressure again a very simple difference plot like the one we showed for temperature just looking at how the pressure patterns have looked over the last several decades compared to the decades before that in the middle part
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of the 20th century the blue colors indicate where there's low pressure so you can think about a low pressure system and counterclockwise flow the red high pressure and so the flow around this being this direction around the low-pressure this way and if you just look at the North Atlantic this flow this change in the circulation has produced more colder Arctic air coming down over this part of the world that relates to that that cold spot and more
44:54
strong west to east flow of relatively warm maritime air during the winter season over Europe and downstream into Asia and that explains dynamic much of the warming that we've seen over that part of the globe these are the kind of things that are very important as you can see it's really occurring on very longtime skills this is just a plot of sea-level pressure over the North Pacific and the difference the gradient and pressure here and I just put these
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they're not really scientifically robust just sort of eye indications with your eye of these different epochs or different periods of time and you can see that these variations are very significant very robust they occur on década land multidecadal timescales so one of the aspects of climate science that we're focusing on quite a bit as to what extent can we predict these and understand these changes and and give society useful information on are we
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going to stay in this regime for another ten years so we're going to shift to that because again it really dominates regional climate variability on fairly large spatial scales all in the background all in the context of an overall changing climate this is just a slide I like to show that kinda illustrates how this problem has been somewhat ignored this is a slightly old article about a decade ago by Edie Hawkins and Rowan Rowan Sutton published
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in 2009 that's looking at some of the model simulations for the fourth assessment report of IPCC back in that point in time there's different emission scenarios here the historical surface air temperature record the observed record and what you can see is that there's various sources of uncertainty when we talk about climate model projections into the future one of those is called forcing or scenario uncertainty what pathway are we going to
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take what are we going to do about emissions of greenhouse gases as we move into the future we can take different approaches and we can either make substantial decreases in emissions or remain on more business as usual path and that produces a range of climate outcomes given by the solid colored lines climate models are also not perfect so if you run a set of diff climate models with slightly different representations of the system because
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the system is very complex and how the physics of the system are represented vary from one model to the next even under the exact same forcing scenario you get a range of responses so if you just look at for instance this blue curve you see that there's a spread of outcomes and the spread is very important to understand and communicate but all these little spaghetti lines which you can't see the individual lines very well here represent then this
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natural variability not just averaging across all the models under all these different scenarios that's what we do in the field of climate science to isolate to depict what the forced climate change signal is which is critically important but we intentionally average out all the natural variability this system which indeed is large and important so this is really the problem is that we have anthropogenic climate change occurring but we have these very large decadal and
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multi decade old variations that can really dictate climate over large portions of the globe and so to what extent is that predictable so we use models this is the model that's been used for this particular study it's called the community or system model patty referred to the fact that I was in charge of climate projects at NCAR one of those projects I served as the chief scientist for the development of this model it's a very complex model for a
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long time climate models really represented what we call the physical climate system representations of the atmosphere the ocean the sea ice and the land surface in various degrees of complexity now we're understanding that it's not just the lower atmosphere that's important for climate but indeed the whole atmosphere extending to outer space the chemistry in the system is incredibly important and we'll hear talks related to that ecosystems and how they're being impacted and how they
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feedback and influence is very important and not only sea ice but land ice Mike referred to his talk yesterday that several decades ago we viewed the Greenland ice sheet the Antarctic ice sheet as something that was going to change on very very long timescales basically these massive blocks of ice we're gonna kind of stay there even in the context of climate change but now we're seeing that they're melting that the dynamics of those systems are changing more rapidly so it's important even for
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studies of the next century or so that we begin to include representations of the ice sheets so this is just a little bit about this model there's a study that was published by some colleagues of mine in the bulletin of the American Meteorological Society and they described a very rich set of runs and perhaps it might relate to some of your individual research interests and we can talk more about these set of runs but the experimental design is basically
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this you you run the model under some pre-industrial control you then begin a what we call a 20th century simulation where we have the best estimates of changes in radiative forcing over the 20th century but in 1920 an arbitrary year but just to illustrate the impacts of unpredictable natural variability what we did was we perturbed just the atmospheric initial state by this very small temperature perturbation at the very lowest levels of the of the
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troposphere of the atmosphere above the surface just barely perturbed it and this is this chaotic effect okay the butterfly effect that Edmunds documented that just a slight perturbation causes the atmosphere and indeed the climate system to go on different trajectories and this relates to the natural variability of the system and what it means is that if we look at projections and we don't average across these just to isolate the greenhouse gas
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force signal it gives us a spread that's inherently unpredictable when we look beyond time skills of maybe 10 or 20 years if we look at say the next 50 years this is what it looks like so we have a control we have an individual member we then perturb it and the gray lines illustrate this spread now the spread doesn't look very impressive and that goes back to the statement that I made earlier ok the natural variability is not going to have a very strong fingerprint when you look at global
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averages or Hemisphere averages or annual averages okay but it certainly does when you look regionally so if we look at climate trends over the next 50 years not just the next ten years but what about the next 50 years what does this imply there's a lot of plots here I've plotted 40 of the 42 ensemble members this is just looking at the change in temperature over the US over the next 50 years okay under the same forcing scenario over the same
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greenhouse gas forcing scenario and you can see a lot of commonalities when we averaged across all of this you can very clearly see that the model projects an average warming over the US it's very pronounced several degrees centigrade especially over the northern regions of North America but if you really begin to look in detail at each one of these individual maps that I would argue are equally plausible outcomes to the extent that the model is representing well the
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the the actual system and we have many reasons to believe it does a very good job in many aspects of representing the climate system you can see that there's really a wide spread of outcomes where for instance portions of the Northwest United States in Western Canada show very pronounced warming but another simulation so much less warming or cooling this is critical information to convey to stakeholders and users of this kind of information we can understand
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that by when we look at an individual model simulation which is a credible simulation of what might happen over the next 50 years we can contrast to ones just to say run a and one B the colors depict the temperature change over North America the contours represent the change in sea level pressure a measure of the atmospheric circulation and you can see two very different depictions one model simulation shows that high pressure is going to increase over the
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North Pacific which produces this direction of a flow again pool takes relatively cool air from the Arctic down into this portion of Canada and the western US in contrast low-pressure affects relatively warm maritime air over this region and really amplifies the warming that we'll see as a response of anthropogenic climate change if you look if you average across all 42 model simulations to look at what the response of the model is to
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greenhouse gas forcing that's the forced response that's common to all of the runs and if you simply subtract the force response from the total that gives you the temperature fingerprint of the internal variability of the system and I think you can see very clearly that fingerprint can be very very significant and so this is something that I think is is equally important to communicate as well so that's my talk I won't take the time to run through the conclusions you
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can read it for yourself and again I hope this kind of hit the mark because it was kind of hard for me to decide exactly what I should focus on in this talk so thank you very much it's a real honor to be here and and I know who I've used up my time but maybe one question right yes well we have our next speaker come on I think I heard a computer sentence so while we're doing that let's take advantage to have a couple of questions for gentleman Ted
55:16
and then yeah and in a paper that we wrote myself with several of the co-authors I listed we talked about that specific problem it all relates a little bit to maybe even some of these like tipping point arguments and whatnot when third and human thresholds were crossed that gives you a better prediction of how the predicted response is going to evolve but still you know I think that the key point is the the amount of natural variability in the system can
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really cause very different trajectories again this is on you know regional spatial scales but what I was hoping to illustrate with those plots is the regional scales aren't very small I mean there have you know there's continental wide scales and so that's very important Don
56:42
yeah it's almost in our analysis it's really strongly doc dominated entirely by the dynamical response of the system and those simulations so it's the changes and sea-level pressure the changes in atmospheric winds the positioning of the jet streams which is entirely dynamical you can actually then regress out that dynamical component and be left with another indication of just the forced response and I think that's very important when we talk about
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comparing models with with observations you know how well does a model capture G's we're not seeing the warming that we've witnessed in the real world it could be that dynamical response and so factoring that dynamical component out I think gives you a true evaluation of how the models perform against observations and model to model comparisons as well all right I think we are out we're gonna cut you off there because R okay speaker thank you sample your sauce with you at
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the break all right Joe around for the break thank you very much thank you
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