Text of John Holdren’s talk at the Stephen Schneider Memorial Celebration, December 12, 2010


Stephen Schneider

John P. Holdren, President Obama’s Advisor for Science and Technology, spoke on “Climate Change Science and Sanity: Steve Schneider’s Extraordinary Contributions to Both” at a memorial celebration attended by hundreds of people on the campus of Stanford University. We were among the attendees at this extraordinary event and appreciate the opportunity to post Dr. Holdren’s excellent talk here.

Stephen Schneider Memorial Celebration, Stanford University, December 12, 2010

Remarks by John P. Holdren, Advisor to President Barack Obama for Science and Technology; Director, White House Office of Science and Technology Policy; Co-Chair, President’s Council of Advisors on Science and Technology

Climate-Change Science and Sanity: Steve Schneider’s Extraordinary Contributions to Both

The three overarching questions in climate science – indeed in any science — are these:  What do we know?  How (and with what confidence) do we know it?  And how can we learn more?  

The one overarching question in climate policy is: What should we do?

And the overarching question at the intersection linking the domains of climate science and climate policy is this:  How can the answers to these questions about climate science better inform the answers at which publics and policy-makers arrive about what we should do?

Steve Schneider was a remarkably prolific, productive, and profound contributor to what we know about climate change.  But he was also among the clearest expositors of how and with what confidence we know it, among the clearest thinkers about how to learn more, and a pioneering contributor to the study of options for what to do and ways to assess their efficacy. 

And no one matched him in his understanding of and ability to improve and work the available mechanisms and communications channels for making the best current knowledge about the science and the options around climate change clear and compelling for students, for the wider scientific community, for policy makers, and for the public.

He used, with consummate skill, virtually every mechanism and communication channel there is.  He was a brilliant classroom teacher and superb one-on-one mentor;  a sought-after lecturer by the most distinguished universities and most prestigious professional societies in the world;  and an unbelievably prolific author and editor of books about climate, ecosystems, and society, of popular as well as professional, peer-reviewed articles, and of op-ed pieces and letters to the editor. 

He was also the creator and editor for 35 years of the pioneering and still unique interdisciplinary journal Climatic Change; a key contributor and wise counselor, from its inception in the late 1980s, in the immensely (and rightly) influential Intergovernmental Panel on Climate Change; a frequent focus of interviews in the electronic and print media; and the architect of the most comprehensive and accessible tutorial website in existence on the history, content, and implications of climate-change science (still to be found, explored, and enjoyed  at http://stephenschneider.stanford.edu/Climate/) .     

To return for a moment to his teaching and mentoring:  Steve was a teacher of exceptional gifts, not only in the clarity, rigor, and infectious enthusiasm he brought to the classroom but also in his uncommon capacity to nurture and grow his students’ and understudies’ curiosity, creativity, and ambition in the best sense – ambition to discover, to know, to share knowledge, and to use it for improving the human condition.   He excelled at this dimension of teaching and mentorship not merely because of his ability to describe the excitement of scientific discovery and how much more of importance is waiting to be discovered, but even more because of the inspiring example he provided of how much one individual, in one lifetime, could discover, know, communicate, and put to use for the betterment of society.

In his teaching, his writing, his interactions with colleagues, and a high proportion of his many interviews there appeared a particular theme about the responsibility of the climate-science community, which was that the community cannot be focused only on advancing the science in all of its facets, as important as that is, but that it must also attend to the processes and packaging by which insights from and about the science enter public understanding and influence public policy.

If that proposition about the scope of the responsibilities of the climate-science community is accepted, one still might suppose that discharging these responsibilities would require that different members of the community specialize in  the different dimensions of the task – some who focus on expanding our understanding of how the climate works and is changing, others on the effects of such changes on ecosystems and society, still others on the options for ameliorating action, and others still on how best to communicate insights about all of this to publics and policy-makers. 

One might suppose this because it seems unlikely that any one individual could have the breadth of skills, depth of intellect, integrative bent, personality, energy, and commitment to be able to make contributions at the highest level of accomplishment to all of these focuses and activities – from fundamental contributions to our understanding of climate change and the epistemology of climate science;  to the elucidation of the intersections of climate science with ecology, economics, sociology, and politics;  to a body of popular books, lectures, and media appearances on climate and society that easily stands comparison with what Carl Sagan did in the popularization of astronomy.

But Steve Schneider did.  He had it all.  He used it all.  And in so doing he showed us the particular power and extraordinary productivity and influence that can come when a single individual embodies all of these talents, pursues all of these agendas, and links them so seamlessly and successfully.

To elaborate a bit on the substance rather than just the character of Steve’s achievements, I want to return to the three overarching questions with which I began these remarks.   What do we know?  How and with what confidence do we know it?  How can we know more?

What we know is that the climate of the Earth has recently been changing in ways highly unusual against the backdrop of natural variations that have operated over millennia.  

We know with very high confidence that the principal driver of these recent changes has been human activities – above all the emission of heat-trapping substances from society’s energy system and from land-use change. 

We know with high confidence that these changes in climate are already causing harm to human well-being in many forms and many places: 

  • in the form, for example, of increases in the frequency and/or intensity of floods, droughts, wildfires, heat waves, and the most powerful hurricanes and typhoons; 
  • in the form of accelerated shoreline erosion and increased saltwater intrusion inland;
  • in the form of alterations in the geographic range and ecology of pests, pathogens, and vectors of human and animal disease; 
  • and in the form of the combined effects of ocean heating and ocean acidification on coral reefs, which together with tropical forests constitute one of the two largest reservoirs of biodiversity on Earth.

And we have much reason to believe that these harms will continue to grow in scale and pervasiveness unless and until society reduces the offending emissions sufficiently to stabilize the concentrations of heat-trapping substances in the atmosphere (although here we have far less confidence about the details because – as Steve Schneider constantly reminded us — predicting the future is harder than understanding the present and the past).

To these crucial things that we know or have good reason to believe about climate change, and to our understanding of the degrees of confidence we can associate with what we know and believe, Steve Schneider made enormous contributions.       

He was a master at using simple but ingenious back-of-the-envelope calculations to begin to clarify issues whose more complete explication would ultimately require combining the most powerful computer models and the most sophisticated observations – which efforts were often both motivated and shaped by the elegant results he first obtained with pencil, paper, and pocket calculator. 

This was true of his pioneering work on the competing roles that atmospheric particles play in climate, in some circumstances warming and in some circumstances cooling, depending not only on the characteristics of the particles but also on the characteristics of the ground or water below and the clouds that might also be present.

The same elegant simplicity of initial analysis, bolstered by subsequent sophisticated computer calculations, was behind his seminal insights about how clouds themselves work in climate – a problem still not wholly solved – notably in his demonstration that not only the area and whiteness of clouds matter, but also, crucially, the height of the tops of the clouds.

He was one of the first to recognize the importance of understanding the “transient” behavior of global climate between the equilibrium associated with the pre-industrial atmospheric composition and the new equilibrium associated with increased atmospheric concentrations of greenhouse gases.

In thinking about that, he was quick to come upon the insight that the slowness with which excess heat is carried downward from the surface layer of the oceans into the depths means that it takes many decades for the climate to reach a new equilibrium following imposition of an increase in greenhouse gases.

This means, in turn, that, at any given moment in a period of rising greenhouse-gas concentrations, we are only experiencing a fraction of the global-average temperature increase and associated impacts that will eventually ensue as a consequence of the concentrations already attained.

And it also means, Steve was quick to recognize, that transient warming will happen at different rates in different places on Earth’s surface – differing even among parts of the ocean with different depths.  This in turn means that the geographic patterns of climate change during the transient will likely differ from the patterns in a new equilibrium after the atmosphere’s composition has stabilized. 

And that means, Steve concluded in 1994, that looking for the “fingerprints” of human as opposed to natural influences on climate in the results of equilibrium climate models is fraught with pitfalls.  This is part of the larger problem of  “signal detection” in climate change – how and when the “signal” of human intervention becomes detectable against the “noise” of natural climate variability – to the study of which Steve contributed a great deal.

The elegant simplicity of the reasoning by which Steve arrived at and explained these and many his other insights about climate change caused many of us to think, afterwards, “Of course!  That’s obviously right.  Why didn’t I think of it?”  But we didn’t, and he did.

Steve was also a master, though, of the more complex disciplines that are part of climate science – for example the numerical techniques underlying the most powerful computer models of global climate, and what errors and uncertainties could be introduced by those techniques in combination with our inadequate knowledge of some of the underlying physical processes.  He knew that insufficient care in the construction and use of these computer models could lead, as he and I used to joke, to “making enormous errors at incredible speed”.

Also in the domain of the more esoteric dimensions of climate science, Steve was deeply knowledgeable about the most powerful statistical techniques for teasing insights out of complicated data sets, and in consequence he was able to identify far more quickly and tellingly than most what the sources and magnitudes of uncertainty and possible error in such analyses were.

Indeed, his clear-eyed focus on the uncertainties in the science of climate change – and his insistence that these be candidly acknowledged and accurately portrayed in every forum, professional or popular, where such science is presented – was a Schneider hallmark.  That particular aspect of his scientific personality and output, all by itself, had a profound and positive impact on the whole field and, notably, on the approach and the publications of the Intergovernmental Panel on Climate Change.

That brings me to Steve’s contributions to the second overarching science question with which I opened these remarks, namely, beyond “What do we know?”…  “How and with what confidence do we know it?”

Because Steve was personally involved in so many different dimensions of climate-change science – in close collaboration and often co-authorship, I should add, with many of the rest of  the best and the brightest from every corner of the climate-science community, so many of whom are here today — he was in an exceptionally good position to pull together all the pieces of “how we know” into the big picture which, because of the complementarity and consistency of the different lines of evidence is truly greater than the sum of its parts.

He was tireless in explaining to the less informed and the skeptical that our understanding of how global climate works and how the build-up of heat-trapping gases is affecting it rests not on speculation or a few untested computer models but on a veritable mountain of evidence including:

  • basic and uncontroversial understandings of how energy interacts with the gases that make up the atmosphere and how the Earth’s water and carbon cycles work;
  • incontrovertible data showing the rapid rise of atmospheric carbon dioxide, methane, nitrous oxide, and halocarbons in the industrial era and equally unambiguous evidence tying a large part of these increases to human activity; 
  • one hundred thirty years of temperature readings by globe-spanning networks of thermometers, as well as similarly long-running and wide-ranging measurements of other climate variables; 
  • the records of earlier climates preserved in tree rings, corals, ocean sediments, fossil pollens, ice cores, and measured temperature gradients in the Earth’s crust; and
  • thoroughly tested computer models of the motions of atmosphere and oceans showing that the sum of human and natural influences as we understand them explains with remarkable fidelity the pattern of changes in global climate that has been observed.

These lines of evidence are documented in tens of thousands of scientific papers by thousands of authors, published over a span of more than fifty years.  They have been scrubbed, reviewed, and re-reviewed by academies of science across the world, by other leading professional societies, and by the Intergovernmental Panel on Climate Change – which I am fond of reminding people, as Steve was – is not the source of our understanding of climate change but only the pre-eminent institutional synthesizer and communicator of that understanding. 

When mistakes are found in the work of the IPCC, as inevitably some will be – or indeed when they are found in the underlying body of peer-reviewed science, as is likewise inevitable – they are corrected.  That process doesn’t cause the edifice to come crashing down;  it strengthens it. 

As Steve was fond of pointing out, the odds are long indeed against our discovering such pervasive and fundamental mistakes and misinterpretations in this immense body of evidence as to call into question the core conclusions about climate change I have summarized here.  And although (as Steve would also point out) there is a value judgment in this next point, it seems the height of irresponsibility for policy-makers asserting the science is wrong to bet the public’s welfare against such long odds.

Before I let that point take us deeper into the intersections of climate science with climate policy, let me say one last thing about Steve’s contributions to climate science itself.  This relates to my third over-arching science question:  “How can we know more?” 

I have mentioned already that Steve was uncommonly gifted at combining fundamental physical understanding and intuition with relatively simple calculations and thought experiments to derive big insights about the science.  The frequent result of his exercise of this gift was identifying key questions and the beginnings of their answers in ways that opened up whole new lines of investigation that others would end up pursuing with extensive programs of measurement, modeling, and further analysis.   He was always asking “How can we know more?”, and not just more in general, but more about the science questions most germane to figuring out what society should do about climate change and when we should do it.  And having figured out such directions, he would politely point the way to the rest of us.

A few of his colleagues, early in his career, thought him guilty of “cherry picking” – plucking the easy results on a given problem and then moving on, while leaving to others the messy task of working out the details.  When I heard such criticism I always responded that I thought it was in fact the highest use of Steve’s extraordinary intellect for him to open up the important new scientific vistas and associated lines of investigation that his students, protégés, and colleagues then pursued to the great benefit of their careers and the field.  Over time, I think just about everybody came to agree with me, but not just because of the force of this argument but also because of Steve’s continuous demonstration that, in illness as well as health, he was just plain working harder than anybody else on whatever most needed doing in the science, its communication, and its application to the development of sound policy options.  

As for Steve’s skills as a communicator about climate science and climate policy, I need not take much of the time of this audience to underscore what you already know.  He was a master at this, and not just in consistently clear and engaging exposition – also nonstop exposition, some would observe – but also in his ability come up with the most telling thought experiments, analogies, and metaphors. 

One of the most famous and effective of these was his “loading the dice” analogy as the answer to the politically debilitating and rather boring proposition that no single instance of extreme weather – no flood, no drought, no super-powerful hurricane – can be attributed to climate change, since any such event could have happened anyway in the absence of such change.  What Steve so tellingly brought to the public debate on this point was that global climate change is loading the dice in favor of such events – increasing the odds of their happening, like dice loaded to produce snake-eyes, and thus increasing the expected frequency of their occurrence.

Steve’s ability to explain why stochasticity and uncertainty should not be used as excuses for inaction on climate change was in fact one of the keys to his effectiveness at the intersection of climate science and climate policy.  As perhaps the pre-eminent scientific analyst of the sources and magnitudes of the uncertainties in climate science, he was in a superb position to explain that those uncertainties provide no basis for complacency but rather in many ways reinforce the case for remedial action – not least because the uncertainties cut both ways:  the actual outcomes from continued high greenhouse-gas emissions could as easily be worse than the current mid-range assessments as better.  Indeed, as Steve and a number of others present here have pointed out, there is much reason to think that they are actually more likely to be worse than to be better.

I titled these remarks “Climate Change Science and Sanity: Steve Schneider’s Extraordinary Contributions to Both”.  Of course his contributions to the science itself, and his exceptional ability to explain the science and its implications in ways that most members of the public and most policy makers could understand, were in themselves also large contributions to societal sanity about climate science and policy.  (Of course, in the current circumstances, one is obliged to say “not quite large enough”, but finishing the job is the task that Steve’s untimely passing has left for the rest of us.)

Steve’s further contribution to sanity on this issue, which should not be forgotten, is the unfailing courtesy, respect, and patience with which he treated everyone who was willing to discuss either climate-change science or policy with him – even including climate-change contrarians some of whose shenanigans have caused others of us to lose patience.  He was such a deep believer in the power of logical argument that he would pursue that route even in the face of considerable reason to doubt its effectiveness with at least some of his interlocutors.

This is to say that, although he was the best there is at demolishing the positions of the deniers and the delayers, he always did it politely.  

Some have said that we will not see the like of Steve Schneider again.  And I have spoken here about the remarkable combination of his intellect, ambition, commitment, communication skills, and unbelievable energy that would seem to make that so.  But I would suggest we must hope that it’s wrong.  The world needs more Steve Schneiders.   The most valuable thing we could do to honor his life and secure his legacy would be to redouble our efforts to inspire, to train, to help, and to honor those young people who have the aptitude and the energy to be, as he was, deep and broad interdisciplinary climate scientists, first class communicators, and committed contributors to the improvement of public policy.  That is surely what he would want us to do.

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1 Response to Text of John Holdren’s talk at the Stephen Schneider Memorial Celebration, December 12, 2010

  1. Ed Walton says:

    A consensus will always demonstrate; a lack of leadership.
    When Galileo was challenge; he went to the top of the tower. Tossed off his weights, and proved he was right.
    When Einstein was challenged; He told them how light would be have during an eclipse. Proving he was right.
    Because todays scholars, have no understanding of science. When challenged; on whether man could cause global warming, they will always call you ignorant.

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