Climate? It’s Complicated

20 October 2023
Climate? It’s Complicated - Featured image

The courage to admit prevailing predictions of the Earth’s future climate are far from certainties makes Judith Curry a rare model scientist, writes IPA Visiting Fellow Stephen Wilson.

Judith Curry has been on a remarkable journey. In 2005 Curry was a professor at the Georgia Institute of Technology, a climate scientist then 23 years on from earning her PhD in geophysical sciences at the University of Chicago. Few would have heard of her.

Climate Uncertainty and Risk: Rethinking Our Response
Judith A. Curry
Anthem Press, 2023, 316pp

In the foreword to her book, Curry describes how the unplanned and uncanny timing of a paper she co-authored on hurricanes—published just after Hurricane Katrina devastated New Orleans—catapulted her into “being treated like a rock star by the environmental movement”. On the other side of the debate she was “targeted as a global warming alarmist, capitalising on this tragedy to increase research funding and for personal publicity, and a threat to capitalism and the American way of life”. This is a reminder, including to this reviewer, of the importance of getting our context and facts right, and avoiding pigeonholing or caricaturing people.

Curry’s response to all this set her on a journey. It also set her apart as a member of a still relatively small cohort of scientists in the world of climate research who have questioned the mainstream and come to adjust their views. To do so has come at a cost for many of them. It is perhaps not a coincidence that climate scepticism would appear to be a luxury beyond the reach of those known in university land as ECRs: early career researchers. Scepticism seems to be positively correlated with seniority of years.

Curry addresses this topic in about a page-and-a-half under the heading ‘Climate Heretics’. The collection of quotes at the start of each chapter, section, and subsection brings light and colour to the author’s words, and shares her influences. We get pithy, insightful, and funny quotes from scientists, philosophers, writers, poets, playwrights, actors, a comedian, journalists, lawyers, institutions, billionaires, environmentalists, climate modellers being honest, Nobel Laureates, and (of course!) Yogi Berra reminding us yet again that “The future ain’t what it used to be”.

The climate system is nonlinear, complex, and not well understood.

Curry is clearly a widely-read and cultured scientist with a wry sense of humour, ensuring her message is very easy to digest. The heretics subsection is no exception, opening with a quote from philosopher Edward Skidelsky:

One of the great achievements of the Enlightenment—the liberation of historical and scientific inquiry from dogma—is being quietly reversed.

The process of ostracism is described, and the labels ‘deniers, heretics, misinformers, and anti-science’ are discussed, with each word footnoted and referenced. Interestingly, nuclear power makes an initial cameo appearance at this point in a revealing quote from an article by historian Naomi Oreskes in The Guardian from December 2015 titled ‘There is a new form of climate denialism to look out for—so do not celebrate yet’:

There is also a new, strange form of denial that has appeared on the landscape of late, one that says that renewable sources can’t meet our energy needs. Oddly, some of these voices include climate scientists, who insist that we must now turn to wholesale expansion of nuclear power.

And so it is that the climate scientist James Hansen—who some may have thought of as a climate alarmist, or even an activist—has found himself bracketed by the likes of Oreskes with the dreaded ‘deniers’ Roger Pielke Jr and Sr, William Happer, Richard Lindzen, John Christy, and Curry. Perhaps people who understand numbers, can do arithmetic, or follow mathematics and logic, and remember something of high school physics and chemistry, are now ‘strange’.

This is all within a section titled ‘Heresy, Doubt, and Denial’, in Chapter Two ‘Consensus, or Not?’ which aptly opens with a quote from English philosopher John Stuart Mill’s On Liberty (1859) that perhaps captures Curry’s disposition on the value of free inquiry in the quest for knowledge and understanding in a real world of uncertainty and risk:

We can never be sure that the opinion we are endeavouring to stifle is a false opinion; and if we were sure, stifling it would be an evil still. … All silencing of discussion is an assumption of infallibility.

The book is organised in three parts: chapters one to four on ‘The Climate Change Challenge’; chapters five to nine on ‘Uncertainty of Twenty-First Century Climate Change’; and chapters 10 to 15 on ‘Climate Risk and Response’. Each chapter is about a dozen or so pages, broken into sections and short sub-sections of a page or so each. The index is good. The footnotes and references throughout the book are extensive and thorough. Each of the book’s 15 chapters is rich with references: I found many to be worth following up. Masterful books such as this, like milestone papers, provide a master key to an entire library.

This book’s structure makes it highly accessible for reading in easy sittings, or the reader can dive into the parts in any sequence of interest. Like me, you may soon find you have read the whole book.

Ongoing research reveals unforeseen complexities in the climate system.

The writing is clear, concise, and very readable. The prose is spare in the manner of the very best scientific papers. Curry never labours the point. Many sentences are gems that reward reading, pausing, thinking, and re-reading. This is a contested field of science described in plain English for the intelligent, curious, genuinely interested, and serious non-specialist.

Have you ever wondered what is inside a Global Climate Model (GCM)? Here are some samples from chapter six on Climate Models:

A wide range of models are used in climate science to study the climate system and its behaviour across multiple temporal and spatial scales. Climate models range from simple energy balance models to exceedingly complex Earth system models. Global Climate Models (GCMs) create a coarse-grained simulation of the Earth’s climate system using computers. …

While GCMs continue to be used by scientists to increase understanding about how the climate system works, their outputs play a central role in developing international, national, and local policies. In the context of the IPCC and the UNFCCC, climate models are used to assess the causes of recent climate change, predict future climate states, provide guidance for emissions reduction policies, support local adaptation policies, and to provide inputs for Integrated Assessment Models to assess the social cost of carbon.

This is followed immediately in the same just-the-facts tone with this:

There is considerable uncertainty and disagreement about the extent to which climate model simulations provide accurate information about the world. Scientists lack the data they need to comprehensively test a model’s performance, and scientists disagree as to which metrics should be used for climate model evaluation.

That last sentence is an example of one that I read, paused, reflected on, and re-read. The same for the very next sentence:

Conclusions about model reliability are made more difficult insofar as the climate system is nonlinear, complex, and not well understood theoretically.

Let that sink in. The read-stop-think-reread process continues:

Initially, climate research programs aimed at the reduction of the uncertainties in climate models. However, since the mid-1990s, it has been increasingly recognized that more research does not necessarily reduce the overall uncertainties regarding future climate change. Ongoing research continues to reveal unforeseen complexities in the climate system that add to the perceived uncertainty of climate models…

A little further on:

Some of the equations in climate models are based on the laws of physics such as Newton’s laws of motion and the laws of thermodynamics. However, there are key processes in GCMs that are approximated and not based on physical laws.

From the sub-section ‘Complexity and Chaos’ is a quote from some modellers being honest:

Since the climate system is complex, occasionally chaotic, dominated by abrupt changes and driven by competing feedbacks with largely unknown thresholds, climate prediction is difficult, if not impracticable.

Curry’s explanation includes this section, which contains more places well worth pausing and thinking:

Many processes in the atmosphere and oceans are nonlinear, which means that there is no simple proportional relation between cause and effect. The nonlinear dynamics of the atmosphere and oceans are described by the Navier-Stokes equations (based on Newton’s laws of motion), which form the basis of prediction of winds and circulation in the atmosphere and oceans. The solution of Navier-Stokes equations is one of the most vexing problems in all of mathematics: the Clay Mathematics Institute has declared this to be one of the top seven problems in all of mathematics and is offering a one million [dollar] prize for its solution.

I distinctly recall the day in 1989 when Professor Tony Perry scrawled the Navier-Stokes equations up on the blackboard in his third-year fluid mechanics class in the Mechanical Engineering School at Melbourne University, and said something very similar to the last sentence above. I am glad Judith Curry has written this. I worry that eyes glaze over when I say it. What does all this mean?

If you have ever been rudely told climate and climate change has nothing to do with weather, and weather uncertainty, read on:

Climate model complexity arises from nonlinearity of the equations, high dimensionality (millions of degrees of freedom), and the linking of multiple subsystems. Weather has been characterised as being in a state of deterministic chaos, owing to the sensitivity of weather forecast models to small perturbations in initial conditions of the atmosphere. The source of the chaos is nonlinearities in the Navier-Stokes equations. A consequence of sensitivity to initial conditions is that beyond a certain time, the system will no longer be predictable in a deterministic sense; for weather, this predictability timescale is a matter of weeks.

Coupling a nonlinear, chaotic atmospheric model to a nonlinear chaotic ocean model gives rise to additional modes of instability and chaos. How to characterize this is virtually impossible under current theories of nonlinear dynamical systems, particularly under conditions of externally forced changes (e.g. increasing concentrations of carbon dioxide). This situation has been referred to as “pandemonium.”

I had thought that climate models could and should be calibrated to historical climate data. Curry explains that all of the GCMs used in the IPCC Fourth Assessment Report (AR4 Climate Change 2007) were tuned (kludged) to “reproduce the time series for the 20th century of globally averaged surface temperature anomalies; … yet they produce markedly different simulations of the 21st century climate”. More recently, the models used for the Fifth and Sixth Assessment Reports (AR5 and AR6) have less tuning and larger discrepancies between simulations and historical 20th century data, presumably as the price for greater alignment between the models’ 21st century projections.

Why the book’s title is about rethinking our response to climate uncertainty and risk is crystal clear. Having spent much of her career in the 1990s “attempting to exorcise the climate model uncertainty monster”, Curry’s thinking began to evolve. Discussion and debate—including with scientists and engineers from other fields who find climate models unconvincing—played a key role in that process. Beyond science for science’s sake, Curry was also influenced by exposure to businesses and corporations asking real questions to try to understand their risks.

The book is also a thoughtful and significant contribution on uncertainty and risk in general.

In recent years, Curry has been employed in the private sector as the president of Climate Forecast Applications Network (CFAN). As she has written extensively on her blog Climate Etc. and discussed in interviews with the likes of Jordan Peterson, how having ‘skin in the game’ (by engaging with real businesses seeking to understand complex sets of real-world risks) has revolutionised her perspective on and understanding of climate uncertainty and risk.

This book clearly represents the distilled essence of a lifetime of experience, work, and reflection. While focused on climate, the book is also a thoughtful and significant contribution on uncertainty and risk in general. It makes valuable contributions on topics such as the interface between science and politics, how we handle disagreements within science, and how scientists communicate with governments and the public.

The book addresses how to think about different types of uncertainty, the role of computer simulation models, and the use (and abuse) of scenarios, and how to respond to risk. The analytical framing is scientific. The synthesis of many parts into a coherent whole is impressive. All is in the context of climate, but the thinking, the writing, and the masterful sweep of the work is such that any business person, professional, academic, politician, or official should have no trouble drawing insights and lessons for a range of other fields.

Do not be surprised if this book comes to be recognised as one of the most important contributions to this field. Buy it. Read it. Share it. Lend it to a university student.

Screenshot of YouTube video of Jordan Peterson interviewing Judith Curry:
Jordan B Peterson: The Models Are OK, the Predictions Are Wrong | Dr Judith Curry | EP 329

Stephen Wilson is an Adjunct Professor at the University of Queensland and a Visiting Fellow at the IPA conducting research into implications for energy security of current policy settings. His undergraduate degree was in engineering, and his PhD in economics.

This article from the Spring 2023 edition of the IPA Review is written by IPA Visiting Fellow Stephen Wilson.

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