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Book review: Climate Uncertainty and Risk

Professor Michael Kelly

Climate change is claimed by many to represent the existential risk to the planet. This claim is accompanied by much lazy thinking, and is not backed up by sound science of the sort one would require in any other context before embarking on the implied changes to the energy and other civil infrastructure of society, or changes to the way of life of the human population. Trivially the planet itself is not at risk, only perhaps the conditions under which humans might inhabit it.

Climate Uncertainty and Risk

There are other major risks to humanity, such as global pandemics like the one we have just and are still experiencing in real time, or mega-volcanos, nuclear war or global financial collapse. Somehow, in the absence of any other real threats to the world since the end of the Cold War, climate change seems to have captured an unreasonably large share of the public concern for the future, and people are pressing for action that will certainly lower the standard of living in the developed countries and stunt the growth of developing ones.

In order to gain a more balanced perspective, the current narrative in the public space needs to evolve. Judith Curry, in her latest book, has tackled head-on two of the most important principles that are missing in the debate, namely uncertainty and risk. This is a most welcome addition to the canon on climate change, and I fully expect it to be widely read and perhaps even more widely cited.

The Intergovernmental Panel on Climate Change is responsible for initiating the poor debate, in that it was constituted, not to look at climate change in the round, but only to the portion of climate change attributable to the actions of mankind. Since the climate system is exceedingly complex, it is not possible to make any clean separation, and the IPCC tends to err on attributing more to humans that might otherwise be the case. While the Working Group reports are hedged with some of the uncertainties, the Summary for Policymakers sedulously excises any such uncertainty, and this is picked up by the mainstream media. This last observation has ill-served serious politicians, but has provided grist to the mill of climate demagogues.

The above paragraphs are included here to establish the background and allow me to indicate why this book is so necessary. The book is divided into three sections: (i) the climate change challenge, (ii) uncertainty: a new framework for the climate change problem, and (iii) climate risk and response.

The climate change challenge

The four chapters in this first section go over familiar territory, but again from a new perspective. Just answering the question ‘What is climate change’ opens not one, but many cans of worms. The idea of a scientific consensus is one to which serious and conscientious scientists have an aversion, as science is always provisional and evolving: settled and agreed frontier science is an anathema. These points are discussed critically, as are the lazy descriptions of people as ‘deniers’ if they have principled criticisms of the science. The response to the climate change challenge, in my opinion, is lacking in any understanding of the integrity of engineering projects that would be a part of tackling the challenge. There is no detailed roadmap (contrast the International Technology Roadmap for Semiconductors; that has kept the IT revolution on its relentless advance since the early 1980s). Dr Curry’s own take is in terms of what it means to maintain resilience and antifragility, and she makes the point that climate change is a ‘wicked problem’ that defies simple solutions. Finally, the chapter on mixing science and politics is important. The canon of good scientific disciplines – of hedging all claims with their intrinsic limitations – fails when confronting politicians who want only simple nostrums to take forward. All sorts of further complications enter the real debate. The very notion of ‘post-normal science’ confuses the issue. I assert that there is no post-normal engineering, as getting on a plane going from Europe to the USA normally has a fixed pre-determined destination, not one that is decided by lots, or debates among the passengers or the whim of the pilot.

This first section is the author’s distinctive take on the whole climate change issue, and sets the groundwork for the two sections that follow.

Climate uncertainty: a new framework

The five chapters here deal with aspects of the future of the earth’s climate, which has been changing for millennia without any inputs from humans. Only for 200 years has there been any – and even now, modest – contribution from humans. In the geological past, there have been times at which all four combinations of hotter and colder temperatures, with more or less CO2 in the atmosphere than now, have been recorded, and indeed the first real flourishing of flora and fauna took place in an epoch that was both warmer and with more CO2 than at present. That fact, in itself, should give pause to the those who are alarmed.

The ’uncertainty monster’ has been presented by the author as an antidote to the more dogmatic claims of some climate scientists. The overconfidence of many in the climate science community in the robustness of their models is exposed – the models run too hot, have done for 30 years or more, and no progress has been made to bring models and reality together. The future extrapolations of the climate are encapsulated in scenarios based on levels of future emissions. After decades, we can rule out the so-called RCP8.5 scenario as extremely unlikely, and yet in the recent IPCC report, nearly 60% of all future projections on climate impacts were taken from this scenario. It is as if all scholars of impacts are trying to outdo each other in scariness, and due moderation is out the window. There are other factors in the geological timeframe of climate, associated with megavolcanoes, solar variations and the natural internal variability of the climate, that have the potential to dwarf the changes being reported in the climate over the last century. It is entirely proper to ask the question ‘What is the most likely worst case?’, which is not the same as ‘What is the worst case you can possibly devise?.

This section really constrains the future possibilities for the climate in the rest of this century.

Climate risk and response

Risk is a part of the human condition – a truly risk averse person would not get out of bed in the morning for fear of what might happen. There are six chapters in this final section. The first two introduce risk assessment and risk management, and draw on literature from the insurance industry and others who deal with risks on a daily basis. It is not as though climate change is the first risk to appear. Decision-making under deep uncertainty is highly topical, as the COVID-19 pandemic has given us many examples of decisions that have been taken in real time when a week is a significant period of time. When the lessons are leaned about the response to this pandemic, there will be much for the climate change community to digest: fortunately, climate timescales are decadal.

There are chapters on each of the two main approaches to a changing climate, adapting to the challenge and mitigating the risk.  At the present level of uncertainty, the former is more rational, and has the advantage of requiring finance, people and materials when the adaptation is seen to be needed, and with immediate benefits.  The Thames Barrier in London is a prime example.  Major floods in the east of England in 1953 would, if only 100 miles further south, have flooded much of London.   A barrier across the Thames was mooted, and actuarial calculation showed that a barrier built in the 1980s would, over its initial design lifetime, save on insurance claims from an otherwise flooded city that would have exceeded the cost of building the barrier: it was built and has saved London from flooding.  Note that the east of England is sinking twice a fast as the sea level is rising. Sea walls around the major cities of the world have been built and can be added to, as and when projected to be needed, at a reasonable cost. The last chapter draws the book together, with the introduction of proper climate risk into the policy discourse. The key objective is to put the genie of apocalypse back in the bottle.


This is a great book of scholarship, properly referenced, and with new and original material from the author and other colleagues. It should be read by everyone with an interest in the future. Climate change is not an imminent existential threat to mankind – that is more likely to be the role of the next pandemic, when a gain of function mutagen exits the laboratory by accident or on purpose.