 My name is Ben Santa. I'm a climate scientist. I study the nature and causes of climate change at Lawrence Livermore National Lab in Livermore, California. Human fingerprints, what are we seeing? Back in the mid-90s, when the first fingerprinting studies were being performed, one of the criticisms of that early work was you folks are only looking at surface temperature. You're only doing this fingerprinting with changes in land and ocean surface temperature. And if there really is a human-caused climate change signal lurking in observations, go see it throughout the climate system. Look in ice, look in the ocean, look in ocean heat content, look in rainfall patterns, the amount of moisture in the atmosphere, the vertical structure of atmospheric temperature change, extreme events. And that's what's happened in the last 20 years now. Scientists have interrogated many, many different aspects of the climate system, not just looking at one number, the average temperature or average moisture or average pressure, but looking at complex patterns of change in hard observations, the latest, greatest satellite observations, the latest, greatest climate model simulations. And the red thread running through all of this fingerprinting work is natural causation alone doesn't cut it. It doesn't explain the changes in all of these things that we've actually observed. My focus has been in the last 10 years or so on two things. One is the vertical structure of temperature changes in the atmosphere. So if you look from the surface of the Earth right up into the stratosphere, 20 miles above the surface of the Earth, what we've actually observed in weather balloon measurements and satellite measurements is this complex pattern of warming low down and cooling up high. So the lower atmosphere, the troposphere, has shown warming pretty much across all latitude bands, and the upper atmosphere has shown cooling over the last 30 to 40 years or so. And it turns out that that pattern of warming low down and cooling up high is really distinctive. We know of no natural mechanisms that can generate something like that, sustain for three or four decades. Volcanoes can't do it, the sun can't do it, internal climate variability can't do it, nor can some combination of natural causes, volcanoes, the sun, and internal variability generate that complex pattern of warming low down and cooling of the upper atmosphere. The only thing that we know of that can generate that distinctive fingerprint is human-caused increase in heat-trapping greenhouse gases and human-caused depletion in the upper atmosphere of stratospheric ozone. And it's been fascinating over my career to look at ever better satellite observations and ever better model simulations and see that fingerprint pattern of human effects literally emerging from the noise. The best information we have now from our most recent research is that the chances of getting a fingerprint match between that human fingerprint pattern of warming low down and cooling up high and purely natural causes is infinitesimally small. The signal-to-noise ratio is greater than 10. That's what our research tells us. So there's just no way of explaining what we've actually observed without invoking a strong human effect on climate. The other thing we've looked at is water vapor. We've looked at satellite-based estimates of the moistening of the atmosphere. And that moistening is kind of interesting because it's consistent with very basic physics and with very basic theory. We know from something called the Clausius-Clapeyron relationship that for roughly every one degree Celsius warming of the lower atmosphere you expect about a 7% increase in the total amount of water vapor in the atmosphere. And that's exactly what we see in models and in observations. And again, it's the pattern matches that are so intriguing there. We see the largest increases in water vapor over the warmest areas of the tropical oceans in both models and in observations. And the bottom line from both the temperature work and the moisture work is what we're seeing is simply not natural. We have not looked at the daily cycle. One of the things we are looking at that I'm really excited about is looking at the annual cycle. Most fingerprint detection work has actually focused on annual averages or decadal averages. People try and beat down the noise of natural climate variability by averaging in space and in time. And that means that one really neglected aspect of change, of human cause change, is the seasonal cycle. So what we're now exploring is whether one can use these formal fingerprinting techniques that we've successfully applied to things like water vapor and temperature to the seasonal cycle. And the answer seems to be yes. We know why that should be. We know in the case, say, of ozone depletion, that has a really clear signature in terms of the seasonal cycle. Other things like biomass burning or changes in sea ice. Again, there's some clear expectation that these things should affect the seasonal cycle, both the size of the seasonal cycle, the timing of the seasonal cycle. And to first order, that's what we're seeing. Some identifiable human fingerprint in the March of the Seasons, which is scientifically rather, how should I say it, scientifically gratifying, but as a human being and as a citizen of this planet, it's kind of disturbing to think that we're now at a point where humans have a detectable signature on the seasons themselves. Perhaps not unexpected again, given what we know about the effects of different factors like human cause changes in greenhouse gases, ozone, biomass burning, and the effects they should have on the seasonal cycle. But still, it's kind of staggering that we might be at a point where we can actually identify these things. And we know that people care about that stuff because that really has implications for plants and animals for phenology, for the timing of events in the natural world. So detection of human effects on the seasonal cycle is not purely of academic interest to a couple of folks at AGU. The 17-year statement, where does it come from, and what do we know about human effects on climate on different time scales? Let me back up a minute. A few years ago, I testified in front of Congress and one of the witnesses in those hearings claimed global warming stopped in 1998, a claim that one has heard a lot in the last few years. And this witness claim that roughly 10 to 15-year periods with little or no warming of the Earth's surface or the lower atmosphere were evidence of absence of human effects on climate. And the witness also claimed that no computer model simulations when run with human-caused changes in greenhouse gases could produce such hiatus or pause periods, again, 10 to 15-year periods with little or no warming. The witness engaged in what I like to call science by eminence of position. Eminence of... eminent physicist, member of the U.S. National Academy of Sciences, but provided no evidence to document or support those claims that were made to Congress. So we decided to do the science to look at those claims and see whether they were correct or not. Well, they weren't. As we and others have shown, computer models even run with historical estimates of human-caused changes in greenhouse gases can, just like in the real world, produce short periods with little or no warming. That's noise. Noise in the system. Our expectation never was, as climate scientists, that each year would be inexorably warmer than the previous year in response to human-caused changes in greenhouse gases. You expect to see some warming signal, but that warming signal is embedded in the rich year-to-year and decade-to-decade noise of phenomenon like El Niños, La Niñas, Pacific Decadal Oscillation. That noise isn't going to go away just because humans are, through burning fossil fuels, changing the chemical composition of the atmosphere. So what we did back then is we looked at all of the world's computer model simulations pretty much then available to us. We showed, first of all, that even models run with historical greenhouse gas increases could, by chance, produce 10 to 15-year periods with little or no warming. We also looked at so-called control runs. Those are simulations with no human-caused changes in greenhouse gases or particulate pollution, no changes in the sun or volcanoes, just rich internal climate variability of these models. Again, things like El Niños, La Niñas, other oscillations of the climate system. And what you could do was then look at those model simulations of a world without us, but with this natural climate variability, you could ask this question, how long would an observed warming trend have to be in order to rise above the model estimates of noise of internal climate variability? And it turned out that the answer was 17 years. We were very, very careful to say we're interrogating these model control simulations and we were not making any kind of prediction at all. That's important. Some critics out there, such as Mr. Anthony Watts of the What's Up With That blog, have maintained that our 2011 paper, where we published this analysis of models and observations, made a specific prediction about the next 17 years. That's a complete misrepresentation of what we actually did. Again, what we were doing was looking at signal-to-noise, saying how long would an observed record have to be relative to model control runs before that observed record was unusual. But of course, in the real world over the last 17 years, we've had many things going on simultaneously, not just internal climate variability. As we and others have shown, there's been volcanic cooling. There's been an uptick in volcanic activity since the beginning of the 21st century. That's not natural climate variability. That, in fact, is an external factor. There's been an unusually long and low solar minimum during the last solar cycle. Again, not pure internal climate variability. Folks like Mr. Watts, who have maintained that all that is going on in the real world is natural climate variability, so the Santorid Al paper is incorrect, are really fundamentally misrepresenting the complex climate system, where multiple things, the sun, volcanoes, internal variability, human influence, are happening simultaneously. Perhaps he can convince some of his followers of the correctness of his interpretation of our results, but he's wrong, and if he really feels so adamantly that the entire scientific community published incorrect science, then it's incumbent on him to set the record straight to publish stuff in the peer-reviewed literature. But sadly, he has not done that. Instead, his focus has been on trying to cast doubt on the motives and reputations of individual scientists rather than to try and truly shed light on complex scientific issues, ashamed of what actually drives scientists. I hear this a lot. Perhaps this kind of criticism was best phrased by Pat Michaels, who famously said, climate scientists are like lab rats waiting for their next cocaine fix, the idea being that we're all just in it for the money or to alter world systems of government to get rich somehow, baloney. I have absolutely no time for people like that who make those kind of claims. It's been my privilege over my career to know men and women who are motivated by desire to understand. That's why they do it. That's why they get up in the morning to try and understand the complex climate system, the factors that influence it, to maybe for one or two moments in their scientific career have a tiny piece of the puzzle that nobody else in the planet has. That's why you do it, for that joy of understanding, for nothing else. So, in my opinion, it's pure projection behavior. The folks who make those kind of allegations are doing quite well for themselves, and they're doing well not because they've made fundamental scientific advances, they're doing well by portraying themselves as the lone wolf howling against the establishment, but they're not creating understanding. I was the convening lead author for the Detection and Attribution chapter of the IPCC's second assessment report back in 1995, and it was unpaid work. It was in addition to my normal responsibilities as a scientist funded by the U.S. Department of Energy, I thought that it was worthwhile to do. Clear assessment of the science, clear explanation to the public and policymakers and other scientists of what we do, that seemed to me to be an important and worthwhile thing, which is why I signed on. I had no idea what I was signing up for. In the end, I do think that the IPCC is still the best mechanism we have for explaining complex scientific issues to both our peers and to the general public and to policymakers, but it is tremendously difficult. You're in a quest for the holy grail of total objectivity. Think about that for a minute. How difficult it is to put aside all those subjective filters through which you see the world, your familiarity with these research methods, or what scientists say, or B, and you don't like scientists C and D. You're asked to put all that aside, and for a couple of years, work on the best possible portrayal of our current state of understanding. Really, really tough, no matter how objective you are. But you have dozens, hundreds of scientists around the world looking over your shoulder, providing input, criticizing you. It's this fierce marketplace of ideas. It's not as some have portrayed it, like Judy Curry, for example, some old boys club where people are just slapping each other on the back saying nice things. That's not the way science works. Not in the IPCC, not at AGU. Again, it's fighting for those, that supremacy of ideas, of theories, of understanding. So really hard, really draining. Very glad I did it in the end. In my opinion, what the IPCC comes out with at the end of this lengthy process is lowest common denominator stuff. And a good example of that is what they've concluded with regard to sea level rise in the fourth assessment report in 2007 and the fifth assessment report in 2013. They, IPCC scientists, found that one of the things we don't understand particularly well at the moment is the contribution to sea level rise from ice sheets on the move, from the dynamics of melting ice sheets. And what they felt they could assess and assess well was the thermal expansion component. So how much sea level rises because of the expansion of warming ocean water. So basically, they punted on the ice sheet contribution and said this could be pretty large, but we don't have the science to reliably assess that at the moment. So what we're going to do is stick to the things that we know well. That is the antithesis of the IPCC as alarmist, scare-mongering organization. That's not the way this organization works. Again, to pass muster to get science through this lengthy multi-year complex review process, you have to have stuff in there that is well-known, that is well understood, that is not speculative. So there are many, many examples like that where rather than going for the big headline, the IPCC instead decided for the things that are really well-known that are not controversial in our field. Well, after the 1995 report came out, I had no idea how my life was going to change. I remember sitting in a bar in Madrid with Steven Schneider, the late Steven Schneider, immediately after the final sentence had been agreed on in the 1995 report, a sentence that's forever engraved on my memory. The balance of evidence suggests a discernible human influence on global climate. And here we are at this bar, and Steve says to me, this changes everything. Your life is going to be changed forever. And I had no idea what he was talking about. I really didn't, quite honestly. I was just relieved that the whole thing was done and I could go back and be a normal scientist again and get back to the research that I loved doing. But he was right. That single sentence had huge ripple effects, not only in the United States, but also in the world. It was the first time the scientific community really got together and said, that's it, it's a complex problem, but we've seen the evidence and it all points in one direction. And we no longer can claim that we're purely innocent bystanders in the climate system. As of 1995, November 1995, Madrid, we had some recognition that we were actively participating in the climate system. So my life changed. Lots of people didn't like that balance of evidence statement and no personal animus, but I was the carrier of that message. So you take down the message by taking down the messenger. I understand that now in retrospect and it was a difficult time because I thought it was at the finish line. I thought it was over and in a sense, it was only beginning. But some things are worth fighting for and that perhaps was the most profound lesson for me back then, that a clear public understanding of the science, doing the kind of thing that you're doing here, that was truly worth fighting for. And I recognized that my responsibilities were not just to do the science, but also to try and tell people, hopefully in plain English, what we did, what we learned, and why it mattered to them. So that was transformational for me to recognize too, what an extraordinary privilege it is to be able to go to work every day and learn something about this amazing world in which we live. And to me, that's the fundamental difference between the folks here at AGU who are trying to advance understanding and the destroyers. People who are not capable of building new understanding, not capable of creating, all they want to do is obstruct, delay, and destroy. They have no real interest in better understanding what's going on in our world. And that's the fundamental distinction to me. You know, on the one hand, people who really do love understanding, and on the other hand, people who really couldn't care less about understanding, they only want to win. Well, one of the tactics was to piggyback off geopolitical events. So that was the time of ethnic cleansing in Bosnia, for example. And the Global Climate Coalition, this consortium of energy interests, produced a document entitled the IPCC Institutionalized Scientific Cleansing. So they argued that we, the scientists involved in Chapter 8 of the Second Assessment Report, the Detection and Attribution Chapter, were guilty of scientific cleansing, of purging our chapter of all uncertainty. It was a lie. That was the astonishing thing to me, that these things were demonstrably untrue. 20% of our chapter was specifically devoted to discussion of uncertainties in observations and climate models, in the statistical techniques used to compare models and observations. So that was really difficult, I think, to get to grips with, to wrap my arms around lying. Lying is a calculated strategy. And getting away with it, too. Being able to make the most outrageous claims. Another claim back then was, and this was from Fred Singer, that changes to the IPCC report had been made by shadowy political operatives for political purposes. They were not under the control of scientists. They had not been approved by the IPCC. All of that stuff was made up. And yet, there were a lot of people who wanted to believe those kind of messages, who wanted to believe, even back then, in shadowy conspiracies on the part of evil scientists to somehow manipulate the world governments and world opinion. That was hard, this sense that no matter how hard you tried, some people were not going to be accessible to rational debate. They were lost. You could never reach them, no matter how compelling your scientific arguments were. Then there were the politicians who got involved, who decided to investigate my funding, why the Department of Energy had allowed me to work on IPCC-related matters. And I guess that was a harbinger, the shape of things to come for the next few decades. Go after the scientists, go after their integrity, go after their funding. Make life miserable for them. Let other people see what's happening. They're probably being employed more extensively and more successfully, too. I think an additional weapon in the arsenal is Freedom of Information Act requests, which are being used not really to advance understanding or, again, shed light on complex scientific issues, but as a tactic to threaten, to intimidate, to throw a spanner in the works to take up your time. Then there's the power of the Internet, which really was not available back in 1995, to harness your supporters to go after individual scientists, send them threatening emails, or worse, and let them know we're watching you and we don't like you, we don't like what you do. That's new. That's a new trick in the arsenal. Hacking emails, releasing them, all of these things. The technology has moved on since 1995, and it's the same playbook. Don't really focus on the science and advancing understanding, contributing, but tear down, destroy. Well, the letter was a letter of support. It was an open letter to Ben Santor, I think was the title of the thing. It was published in the bulletin of the American Meteorological Society. I had no knowledge that this letter was being written, and it was by Rick Antheys, the president of UCAR, the University Corporation for Atmospheric Research, Susan Navery, and two other signatories. I don't remember their names at the moment, but it was very, very gratifying. I think in the middle of all of that stuff that was going on in the summer of 1996, the scientific cleansing charges, the charges that Chapter 8 had been tampered with for political purposes, the charges of irregularities in my own personal research, those were very, very serious allegations. And here, people who I hadn't met, who didn't know me, were coming to my defense and writing this letter and saying, hey, this is not the way to have a debate about climate science, the implications of climate science by going after individuals. And that was the silver lining for me, that many people who had no knowledge of me or what had happened in Madrid were willing to say, hey, this is not the way to have a responsible discussion. Don't try and demonize individual scientists here. That felt really good, as did the New York Times piece by Bill Stevens, also in the summer of 1996, when that came out and gave some real in-depth discussion of what had actually happened. Up to that point, you know, all the attacks were out pretty quickly, but really no space, not much space, was given to the responses to the kind of criticisms that I just mentioned, the scientific cleansing, political tampering, irregularities in research. And I guess that's a strategy too. You overwhelm the press with lots of allegations and they receive front-page coverage, but the detailed, thoughtful responses to those allegations, those are not news, really. The IPCC did respond, I believe. You know, in the end, Bert Boleyn, the chairman of the IPCC and the co-chairs of the IPCC, Sir John Houghton and Louis Guilvan-Mirafilio did respond to the Wall Street Journal, addressed these charges and said, hey, these are wrong. These are just incorrect, you know. We were there. Chapter eight was discussed at this Madrid plenary meeting of the IPCC. There was a clear understanding that the language of the chapter needed to reflect the discussions of the governments present at Madrid, of the scientists present at Madrid. So Ben Center did not behave improperly. That was obviously gratifying. And slowly, but surely, I think the story did come out just like with Climategate. It took a while for the true story of those emails to be told. And that's frustrating when you're right in the middle of all of these things, when you see stuff that is written about you that maybe millions of people are going to read that you know is untrue. And you've got to kind of grin and bear it. But again, worth doing in the end, I'm very glad that I had the enormous privilege of serving as convening lead author back in 1995. If asked, you know, if I could do that simulation and go back, I would do it again. We know beyond a shadow of a doubt that we've changed the levels of heat-trapping greenhouse gases in the atmosphere. It's not a belief system. It's not my opinion. That's fact. We've monitored levels of carbon dioxide and other heat-trapping greenhouse gases for over half a century now at dozens of locations around the world. Those measurements tell a really clear story. Levels of atmospheric CO2 have increased about 40%. CO2 is a greenhouse gas. It traps heat that would otherwise escape out into space. And by looking at lighter and heavier isotopes of carbon, we know that most of that increase in carbon dioxide is us, is burning of fossil fuels. No doubt, no ambiguity. The real pedal to the metal question has always been how much climate change comes from that human-caused change in levels of heat-trapping greenhouse gases. And that's where all the fingerprinting comes in, that not just our group, but dozens of groups around the world have done. Again, as I mentioned earlier, we've looked everywhere, not just at surface temperature, but in the oceans, in the upper atmosphere, in water, in continental runoff from major rivers, in ice. And no matter where you look, nature alone can't explain the changes that we've seen. The best explanation of all of these independently measured things in the real world is a strong human influence. I wish it were otherwise. I truly do. I have a son. He's going to be living to see 2100. He'll know. And my real concern is that he doesn't look back one day and say, hey, my dad knew this stuff. He knew what was going on. Why didn't he try a little bit harder? He had knowledge. He had understanding of what was actually going to happen. And I don't want to have him retrospectively looking back and thinking my dad could have done more, but didn't. It's been a real privilege to watch him grow up. In addition to the scientific imperative to understand this problem, I really do believe there's a moral and ethical imperative too. Like me, my son's a climber. I've taken him climbing since he was a little kid. And the idea that some of the places, some of the glaciers I stood on, some of the ice fields that I've now visited in Alaska, he will experience them fundamentally different from the way that I experienced them. That's not just a scientific issue. That's a moral and ethical issue as well.