Unsettled: to what extent do humans contribute to climate change?

The 26th UN Climate Change Conference of the Parties (COP26) began this week, with an introduction by, among others, the People's Advocate Sir David Attenborough, who made an impassioned plea to world leaders to act now to avoid the approaching apocalypse. 

Climate change is a reality, no sane person can deny the evidence of that, but in terms of the cause of climate change, and how we should deal with it, is the science settled? There have been "heated" debates on the blog over the years, with eminent geologists, such as Australia's Prof. Ian Plimer arguing that the climate is changing solely due to natural phenomena (posting of 20th October 2009), while climate scientists such as the UK's Prof. Stephan Harrison argued to the contrary (posting of October 31st 2009), that the changes are solely due to human actions.

Who is right, who should we believe? There have been many books, mainly by psuedo-scientists, debunking global warming as a hoax, but not so many by respected scientists who can examine the science and its foibles and present coherent assessments.

I have had long discussions with Prof. John Ralston, the founding Director of the University of South Australia's Wark Institute, and a former South Australian Scientist of the Year (posting of 27th May 2014), and he shares my views about the need for an objective assessment of the various contributions to global warming, so I was pleased when he recommended a controversial new book which the author claims puts forward a balanced view of climate change and man's influence.

Unsettled: what climate science tells us, what it doesn't and why it matters, is a book published this year, and by an author, Steven Koonin, who has the right credentials, expertise and experience to ask the right questions and to give realistic answers.

Prof. Koonin is a leader in US science policy and former science advisor for the Obama administration. With more than 200 peer-reviewed papers in the fields of physics and astrophysics, scientific computation, energy technology and policy, and climate science, he was a professor of theoretical physics at Caltech, also serving as Caltech’s Vice President and Provost for almost a decade. He is currently a University Professor at New York University.

The earth's temperature arises from a delicate balance between warming sunlight and cooling heat radiation, which is disturbed by both human and natural influences, with greenhouse gases playing an important role. As everyone knows, CO2 is a potent greenhouse gas, and its concentration in the atmosphere has increased since 1750 from 280 parts per million (0.028%) to 0.0413% in 2021, and continues to rise by about 2.4 ppm every year. Although most of today's CO2 is natural, there is no doubt that this rise is, and has been, due to human activities, primarily the burning of fossil fuels. This CO2 added by humans over the past 250 years has increased the atmosphere's ability to impede heat and is exerting a growing warming influence on the climate, which Koonin fully acknowledges. He does not know of any expert who disputes that the rise of CO2 concentration over the past 250 years is almost entirely due to human activities. However, he feels that the human influence on temperature is physically small, and there are more powerful natural forces, such as volcanoes, the sun, deep ocean currents, driving the climate as well, and they illuminate the scientific challenge of understanding these natural influences well enough to confidently identify the climate response to human action. The real question is not whether the globe has warmed recently but rather to what extent this warming is being caused by humans.

The CO2 emitted by burning fossil fuels disrupts the balance of the great carbon cycle, since that carbon has been pulled out of the deep underground, where it was isolated from the natural processes.  Koonin says, however, that human-emitted CO2 is a relatively small add-on to the vast natural cycle of carbon moving among the earth's crust, oceans, plants and atmosphere.

According to Koonin, the study of climate and energy is the ultimate multidisciplinary activity, no single researcher is able to be an expert in more than two or three of its aspects. Usefully describing the earth's climate remains one of the most challenging scientific simulation processes there is. The multitude of climate models disagree with, or even contradict, each other, and he says that a vague "expert judgement" has sometimes been applied to adjust model results and obfuscate shortcomings. As such the science is insufficient to make useful projections about how the climate will change over the coming decades, much less what effect our actions will have on it. 

Koonin says that is has become de riguer for the media, politicians, and even some scientists, to implicate human influences as the cause of heat waves, droughts, floods, storms and whatever else the public fears. The on-the-scene reporting is powerful, and often moving, and our poor memories of past events can make "unprecedented" quite convincing. But he argues that the science tells a different story,  the World Meteorological Organisation saying in November 2020 that any single event, such as a severe tropical cyclone, cannot be attributed to human-induced climate change, given the current status of scientific understanding. He says that observations extending back over a century indicate that most types of extreme weather events don't show any significant change, some having actually become less common or severe.  There will be many unconvinced by this, as 2021 has been the hottest year ever recorded, with millions of people living with extreme temperatures and facing a growing threat of flooding or wildfires. 

Koonin stresses that open debate is the heart of the scientific process, and it is absurd that scientists should fear being labelled anti-science for engaging in it. William Hogan, Professor of global energy policy at Harvard Kennedy School has said that rather than an existential crisis we face a wicked problem that requires a pragmatic balancing of costs and benefits and feels that Koonin's book is essential reading and a timely breath of fresh air for climate policy. 

However, others have negative responses to the book. Bob Ward, the policy and communications director at the Grantham Research Institute on Climate Change and the Environment at the London School of Economics and Political Science finds that the book is based on a number of inaccurate and misleading claims, flawed studies, and cherry-picked information.

Gary Yohe, Professor of Economics and Environmental Studies, Emeritus, at Wesleyan University in Connecticut, writing in Scientific American, feels that Koonin is wrong and that the science is stronger than ever around findings that speak to the likelihood and consequences of climate impacts, and has been growing stronger for decades.

Dr. Mark Boslough, who has served on the Executive Committee of the American Physical Society Topical Group on the Physics of Climate, has strong criticism, saying that Koonin creates an illusion of arrogant scientists, biased media, and lying politicians – making them easier to attack. 

He asks why does Koonin think that unsettled questions in climate science are any kind of comfort when the consequences of doing nothing can be catastrophic, as predicted by Sir David at COP26? Exactly my feelings. As the degree of human influence on climate change is unsettled, we should assume the worst and make every attempt to phase out fossil fuels as soon as we can, bearing in mind that there must be a transition period when these fuels will be needed to build the new generation of electric vehicles and renewables. Even if Koonin is right, we must still do this, as fossil fuels are the world's major source of air pollution, one of the globe's biggest killers.

It won't be easy however. As Koonin states, the world will need much more energy in the coming decades. Today's global population of just under eight billion will grow to over nine billion by mid-century, with virtually all that growth occurring outside the developed world. Currently fossil fuels provide about 80% of the world's energy and this dominance is projected to persist through mid-century, although a strong growth in renewable sources will decrease the share of the world energy provided by fossil fuels to about 70%.

It will be interesting to see if anything significant comes out of COP26. Stronger international collaboration is required to achieve net zero emissions, and this might not be forthcoming. High emitting developing economies are expected to increase emissions significantly by 2030. China (the world's #1 emitter) and India (#3) are building coal-fired power stations that will double and triple their emissions respectively, and Russia (#4) also proposes investments that will increase its emissions substantially.

Koonin believes that due to the uncertainty the societal response will be to adapt to a challenging climate, and that adaption will very likely be effective. Only time will tell; the climate is changing, humans are playing a role, but our global energy needs are growing too.

It will be interesting to hear what blog readers think!

@barrywills