Separating is hard. I’ve spent most of my scientific career trying to separate observed climate records into human-caused signals and the background noise of natural variability. It’s been challenging and fascinating work. Challenging because so many different human and natural factors affect Earth’s climate. Each factor varies in space and time. We’ll never have perfect understanding of these variations.

It’s been fascinating work because science is ultimately about learning. Since the late 1970s, scientists have learned to recognize the characteristic fingerprints of human and natural influences on climate. Through this work, we know that humans are active agents of change in the climate system – not innocent bystanders. By burning fossil fuels, we’ve warmed our planet. That warming signal is now pervasive and irrefutable.

It’s been a rare privilege to have witnessed this evolution in scientific understanding and to have played a small part in it. 

Separating is also hard in real life. It’s tough to deal with the abrupt ending of a relationship, a marriage, or a friendship. It’s challenging to cope with the ending of long-term employment. There are many aspects of disentangling: financial; emotional; loss of identity, of meaning, of a shared vision of the future, of a daily routine. How will the separation affect those around you? What does it mean not only for you, but for family, friends, and colleagues?

The path from ‘heroic figure’ to ‘villain’ to … ‘Keep building’

I retired from Lawrence Livermore National Laboratory (LLNL) on October 1, 2021. I was at LLNL for nearly 30 years. Almost all my work was funded by the U.S. Department of Energy (DOE).

One part of my job at LLNL was to evaluate computer models of the climate system – to compare models and real-world climate data in a variety of different ways. To see how well climate models captured climate reality. Another part of my job was to fingerprint the climate system. I used pattern-based “fingerprint” methods developed by Professor Klaus Hasselmann to separate climate signals from intrinsic climate noise.

Let’s talk briefly about this separation problem. Climate change is both internally generated and externally forced. The internally generated part arises from a veritable “zoo” of intrinsic modes of natural variability. Some of these zoo inhabitants are well-known outside of scientific circles, such as El Niños and La Niñas. Other zoo denizens – like the Madden-Julian Oscillation – are less familiar to the public. Together, these internal oscillations generate climate variability on a wide range of different space and timescales. This is the background noise against which a human-caused global warming signal must be identified. 

External influences on climate are fundamentally different beasts. They involve changes in factors external to the physical climate system, such as human-caused increases in atmospheric greenhouse gas levels or purely natural fluctuations in the Sun’s energy output. Each external influence causes a unique pattern of climate change – a fingerprint. The uniqueness can show up in geographical patterns of climate change, or in patterns that are slices through the vertical extent of the atmosphere or oceans

The main reward? ‘The work itself’

It’s interesting to muse about internal and external influences on our own lives. After my nearly three decades of fingerprint research with LLNL and the DOE, I now understand that a sense of self-worth must be internally generated. It can’t depend on external influences. If you rely on external feedback from large, bureaucratic institutions for your sense of who you are and what you’ve accomplished scientifically, you can be lost.

A related “lesson learned” is that the work itself is the main reward. Prizes, accolades, and external praise are not the reason you do the work. Praise for your research often depends on the vagaries of the political climate. Under one administration you are presented as a heroic figure. Under a different administration you are portrayed as a villain.

How can this be? You are the same person, doing the same research. You are neither a hero nor a villain – just someone who loves his job. The internal knowledge that the research you’ve published is sound and novel and that it helps to advance understanding should be enough for you. That’s what matters. The respect of knowledgeable peers matters. Everything else is background noise. 

Lesson learned – Speak science to power

I have one final “lesson learned” from the past 29 years. My time at LLNL taught me that scientific understanding is always under attack by powerful forces of unreason. Such attacks cause great harm. They must be opposed. Demonizing science and scientists is dangerous for our health and for the health of our planet.

When ignorance and alternative facts are elevated in public discourse, it’s critically important for scientists to speak science to power. To declare in public what they’ve learned, how they’ve learned it, and why that understanding matters. Remaining silent is not an option when well tested science is presented as unsettled or incorrectly dismissed as a hoax.

I’m proud of the fact that in my 29 years at LLNL, I defended LLNL’s technical work on climate fingerprinting, even when such defense was politically inconvenient. I did not hide. I did not remain silent. I stood behind IPCC findings of a “discernible human influence on global climate”. I stood behind LLNL’s findings of ubiquitous human fingerprints in the climate system.

Get the science right: ‘Unequivocal’ human influence on climate

Getting the science right was always my prime directive, and it was the prime directive of all my colleagues. At the end of days, that’s how we’ll be evaluated – on whether we got the science right. As the IPCC’s Sixth Assessment Report clearly shows, we did get the detection and attribution science right. Human influence on climate is now unequivocal.

I will miss my colleagues at LLNL. I’ll miss the impromptu scientific conversations in our little break room. The excitement of scientific minds at play, exchanging ideas, interpreting complex data, mapping out new studies, seeing interaction terms between different research projects. I’ll miss watching younger colleagues grow as scientists and become leaders in the field. I’ll miss learning how to harmonize in our LLNL band – The Climate Changers – even as we were learning how to harmonize our research and collaborate effectively.

Even though I’ve left LLNL, those friendships and collaborations will endure. And there will be new friendships and collaborations with new colleagues. That is the real award and reward in science – working towards a common goal with brilliant women and men around the world. The common goal? To build a better understanding of Earth’s complex climate system, and of the strange and beautiful world in which we live. Although I’m officially an “old dude” now, I fully intend to keep building.

Ben Santer is a John D. and Catherine T. MacArthur Fellow.


7 top scientists offer tributes to Santer’s career

Yale Climate Connections invited seven world-class climate scientists to share their views on scientist Ben Santer’s three decades of climate science research and communication. Following are their unedited first-person statements, listed alphabetically by last name. YCC invites others, scientists and non-scientists alike, wanting to acknowledge Santer’s accomplishments to send an email to editor@yaleclimateconnections.org.

Richard B. Alley
The Pennsylvania State University

Ben and I testified as part of a larger panel to the Subcommittee on Energy and Environment of the Science and Technology Committee, US Congress, November 17, 2010, on “A Rational Discussion of Climate Change: The Science, The Evidence, The Response.” Most of the discussion was rational, but not quite all of it.  Ben was brilliant, incisive, and accurate, providing the world-class science that he makes look routine. And, when misstatements were made, he positively vibrated with suppressed tension while waiting for the opportunity to refute them – permitting inaccuracy to stand for even a few moments was a real challenge for him. This unsparing intellectual honesty shines through in everything he does, to the good of all of us. 

Kerry Emanuel
Massachusetts Institute of Technology

Others will have spoken about Ben Santer’s highly important and significant contributions to climate science, but here I want to pay tribute to just a single example of Ben’s outstanding leadership in fighting disinformation about climate. I had the privilege of working with Ben and several other prominent climate scientists, under Ben’s leadership, to respond openly and publicly to the promise by one of the two presidential candidates in 2016 to withdraw the U.S. from the Paris Accord. The result was a concise, hard-hitting and effective rebuttal of disinformation and affirmation of the validity of climate science, signed by hundreds of prominent scientists, including 30 Nobel laureates. More than its effect on the public debate, the whole process served to inspire the community of climate scientists who had labored under continual assaults by public figures and others. For this, in addition to his many other accomplishments, we are all indebted to Ben Santer.

Michael Mann
The Pennsylvania State University

Ben is one of my heroes. He has fundamentally advanced our science and has played a key role in communicating its implications to the public and policymakers. And he’s paid a huge price for doing so. He was in the crosshairs of the climate denial machine years before I found myself there, and his friendship and mentorship was critical to helping me deal with their attacks over the years.

Linda Mearns
University Corporation for Atmospheric Research/National Center for Atmospheric Research

My favorite experience of working with Ben was during the 2011 Schneider Symposium, celebrating the contributions of Stephen H. Schneider to climate science and global change. Ben and I co-chaired the session toward the end of the symposium when various folks got up to share their memories and appreciation of Steve. We were a little concerned about this, since we expected more than a few people would break down in tears during their comments. And that was indeed the case, particularly among his former Stanford graduate students. Ben and I very carefully discussed the situation; we realized it would be difficult to interrupt a weeping student and tell him/her that their time was up. These comments were supposed to be very short (like 3 minutes at most). Ben and I somehow managed to gently interrupt people who were running on too long, and sorrowfully but firmly indicate that their time was up. This was one of the best collaborations I have ever been involved in. Moreover, Ben has been the kindest, and one of the most sincere colleagues, I have had the privilege of knowing.

Jerry Meehl
University Corporation for Atmospheric Research/National Center for Atmospheric Research

Ben Santer is perhaps the most careful and conscientious scientist I have ever known, and these character attributes have propelled him to the top levels of climate science.  He’s serious about maintaining these attributes in the face of withering attacks from numerous sources over the years. These attacks are nearly all on his character, not his science. This is a political tactic that we, as scientists, are not used to facing. But, with Ben, we all had to learn this the hard way after he was the first to receive very high-profile character attacks after the IPCC plenary in Madrid. The objective is that if you bring someone’s character down, their science will collapse in a heap of shattered credibility. This tactic failed totally when turned on Ben because, through it all, he persevered with his notable careful and conscientious approach that fortifies his character and his science, and makes him unassailable. Ben is firm in the belief that, in the end, the science will prevail. He is correct in this belief, and his character and his science are beacons to guide present and future scientists through the turbulent confluence of policy and science.

Susan Solomon
Massachusetts Institute of Technology

Icons are few and very far between, and Ben Santer is one of the great icons in climate science. He is admired by every thoughtful reader of his astonishing string of seminal papers, and he is appreciated by the public who are lucky enough to learn about climate change from a master communicator. While he is departing from Livermore after many years of amazing achievements, I have no doubt that this is only the beginning of Ben 2.0 (or is it 3.0?) whose landmark work will continue for many years. I’m honored to be a colleague and friend of this great human being and even greater scientist.

Lonnie Thompson
The Ohio State University

Ben Santer conducted groundbreaking research on “fingerprints” of human impact on climate change, which in part led to the controversial but prescient 1995 IPCC statement concerning “a discernible human influence on global climate.” As is often the case with such research that attains prominence, his findings often attracted vociferous commentary. Ben has been a staunch defender of the rights and duty of climatologists to publish and defend impactful research showing that human activities have significantly changed global climate. Like me, Ben has always had a great appreciation of mountains and alpine glaciers. There is something about the effort required to get to these areas and the clarity of the air and the water, that allows for clear and uninterrupted thought and hopefully now Ben will have more time to enjoy them.