The Climate Demon: Past, Present, and Future of Climate Prediction

Cambridge University Press (published October/December 2021)

An introduction to the complex world of climate models that explains why we should trust their predictions despite the uncertainties.

The Climate Demon (book cover with butterfly image)

Climate predictions – and the computer models behind them – play a key role in shaping public opinion and our response to the climate crisis. The 2021 Nobel Prize in Physics recognized this by honoring climate scientist Suki Manabe for his pioneering contributions to the physical modelling of Earth's climate. The Climate Demon provides an "under the hood" look at the models built by Manabe and other scientists that are used to predict the future of our climate.

Written by an experienced climate scientist, but aimed at the general reader, the book uses simple language to describe the scientific and philosophical foundations of climate models. It explains how to interpret and use the predictions they provide, and argues that we need to trust the models despite their uncertainties. The book cautions that deterministic thinking can mislead us when assessing the risks of climate change, and that we should take climate predictions seriously, but not literally.

Where to buy:

You can preview the book on Google Books and purchase the e-book version on Google Play or the Kindle version on Amazon.

If you are in the UK/Europe, you can order a printed copy from Blackwells (UK), Amazon (UK), and other book stores; In the US, you can order it from Amazon (US) and other bookstores. You can also order it from the Cambridge University Press Bookshop.

  • Covers the fascinating and intertwined history of digital computers and climate models from the mid 20th century to the present – from the weather forecast made by ENIAC, the first digital computer, to climate projections that will soon run on massive Exascale supercomputers.

  • Provides a frank assessment of the strengths and limitations of climate models, and advice on how best to interpret and use climate predictions for impact and risk assessment.

  • Title refers to a recurring philosophical theme in the book, the notion of a Climate Demon – a metaphor for a model that accurately calculates the trajectory of future climate. It is the climate analog of the philosophical concept known as Laplace’s Demon.

  • Cover photo shows a monarch butterfly — a metaphor for uncertainty in prediction that faces an uncertain climate future.


“A wide-ranging guided tour of the modern science of climate prediction, told by a leading expert without jargon or mathematics, and illuminated by history, philosophy, technology, and even literature.”

RICHARD C.J. SOMERVILLE, Scripps Institution of Oceanography, University of California, San Diego

“I thoroughly recommend this book if you want to understand the science behind these all-important [climate] models.”

TIM PALMER, University of Oxford

“If you wish to correctly interpret climate modeling results, read The Climate Demon. Saravanan’s brilliant and humorous book helps both scientists and the general public objectively understand strengths and limitations of climate predictions.”

SAMUEL SHEN, San Diego State University

“… a first rate, well-researched summary and analysis of how predictions in climate science work ... a must read for natural and social scientists from all walks of life, as well as policymakers and managers.”

GERALD R. NORTH, Texas A&M University

Other aspects of the book liked by readers:

    • discussion of the different kinds of models, which is not widely appreciated

    • explains in detail how models are wrong but still useful

    • description of the immense complexity and computational requirements of climate models (it takes a lot more than a laptop!)

    • the notion that we are all steeped in determinism, but shouldn't be

Book Structure

The first part of the book (The Past) features the stories of computing pioneer John von Neumann at the Institute for Advanced Study in Princeton, who helped make the first digital weather forecast, meteorologist Ed Lorenz, who discovered the Butterfly Effect, scientist and women’s rights pioneer Eunice Foote, who connected carbon dioxide with heating, climate scientist (and 2021 Nobel Laureate) Suki Manabe, who used computers to model the Greenhouse Effect, planetary scientist Jim Hansen, who raised public awareness of the problem of global warming, and atmospheric chemist Susan Solomon, who deciphered the mysteries of the Ozone Hole. (Punxsutawney Phil, the prognosticating groundhog, makes a cameo appearance.)

The second part (The Present) discusses the current challenges faced by climate prediction, such as the inexorable increase in model complexity, “tuning” of models to compensate for errors, and the need for model diversity. The distinction between well-known unknowns and poorly known unknowns, and the pitfalls of translating climate predictions for the general public, are also discussed.

The third part (The Future) describes trends in climate prediction driven by recent scientific developments such as geoengineering, the demise of Moore’s Law of ever faster chips, and the advent of machine learning. The book concludes with a discussion of philosophical and practical issues in assessing the impacts and risks of climate change.

A central theme of the book is that climate models are metaphors of reality – their predictions should be taken seriously, but not literally. There is deep uncertainty regarding predictions of extreme climate change scenarios, but this uncertainty is by no means a reason for inaction. If anything, the uncertainty adds urgency to the need to rapidly eliminate carbon emissions. The predictions we have now are confident enough for us to justify strong action, but uncertain enough for us not to panic over doomsday scenarios.

Book Resources

Samples from the book

Additional resources

  • FANAQ (Frequently And Never Asked Questions)

  • Visuals (cartoons, memes, ...)

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