The Physics of Climate Change
Post Hill Press (March 2021)
In the past years, media coverage of climate change has noticeably shifted. Many outlets have begun referring to it as “climate crisis” or “climate emergency”, a mostly symbolic move, in my eyes, because those who trust that their readers will tolerate this nomenclature are those whose readers don’t need to be reminded of the graveness of the situation. Even more marked has been the move to no longer mention climate change skeptics and, moreover, to proudly declare the intention to no longer acknowledge even the existence of the skeptics’ claims.
As a scientist who has worked in science communication for more than a decade, I am of two minds about this. On the one hand, I perfectly understand the futility of repeating the same facts to people who are unwilling or unable to comprehend them – it’s the reason I don’t respond when someone emails me their home-brewed theory of everything. On the other hand, it’s what most science communication comes down to: patiently rephrasing the same thing over and over again. That science writers – who dedicate their life to communicating research – refuse to explain that very research, strikes me as an odd development.
This makes me suspect something else is going on. Declaring the science settled relieves news contributors of the burden of actually having to understand said science. It’s temptingly convenient and cheap, both literally and figuratively. Think about the last dozen or so news reports on climate change you’ve read. Earliest cherry blossom bloom in Japan, ice still melting in Antarctica, Greta Thunberg doesn’t want to travel to Glasgow in November. Did one of those actually explain how scientists know that climate change is man-made? I suspect not. Are you sure you understand it? Would you be comfortable explaining it to a climate change skeptic?
If not, then Lawrence Krauss’ new book “The Physics of Climate Change” is for you. It’s a well-curated collection of facts and data with explanations that are just about technical enough to understand the science without getting bogged down in details. The book covers historical and contemporary records of carbon dioxide levels and temperature, greenhouse gases and how their atmospheric concentrations change the energy balance, how we can tell one cause of climate change from another, and impacts we have seen and can expect to see, from sea level rise to tipping points.
To me, learning some climate science has been a series of realizations that it’s more difficult than it looks at first sight. Remember, for example, the explanation for the greenhouse effect we all learned in school? Carbon dioxide in the atmosphere lets incoming sunlight through, but prevents infrared light from escaping into space, hence raising the temperature. Alas, a climate change skeptic might point out, the absorption of infrared light is saturated at carbon dioxide levels well below the current ones. So, burning fossil fuels can’t possible make any difference, right?
No, wrong. But explaining just why is not so simple...
In a nutshell, the problem with the greenhouse analogy is that Earth isn’t a greenhouse. It isn’t surrounded by a surface that traps light, but rather by an atmosphere whose temperature and density falls gradually with altitude. The reason that increasing carbon dioxide concentrations continue to affect the heat balance of our planet is that they move the average altitude from which infrared light can escape upwards. But in the relevant region of the atmosphere (the troposphere) higher altitude means lower temperature. Hence, the increasing carbon dioxide level makes it more difficult for Earth to lose heat. The atmosphere must therefore warm to get back into an energy balance with the sun. If that explanation was too short, Krauss goes through the details in one of the chapters of his book.
There are a number of other stumbling points that took me some time to wrap my head around. Isn’t water vapor a much more potent greenhouse gas? How can we possibly tell whether global temperatures rise because of us or because of other, natural, causes, for example changes in the sun? Have climate models ever correctly predicted anything, and if so what? And in any case, what’s the problem with a temperature increase that’s hard to even read off the old-fashioned liquid thermometer pinned to our patio wall? I believe these are all obvious questions that everybody has at some point, and Krauss does a great job answering them.
I welcome this book because I have found it hard to come by a didactic introduction to climate science that doesn’t raise more question than it answers. Yes, there are websites which answer skeptics’ claims, but more often than not they offer little more than reference lists. Well intended, I concur, but not terribly illuminating. I took Michael Mann’s online course Climate Change: The Science and Global Impact, which provides a good overview. But I know enough physics to know that Mann’s course doesn’t say much about the physics. And, yes, I suppose I could take a more sophisticated course, but there are only so many hours in a day. I am sure the problem is familiar to you.
So, at least for me, Krauss book fills a gap in the literature. To begin with, at under 200 pages in generous font size, it’s a short book. I have also found it a pleasure to read for Krauss neither trivializes the situation nor pushes conclusions in the reader’s face. It becomes clear from his writing that he is concerned, but his main mission is to inform, not to preach.
I welcome Krauss’ book for another reason. As a physicist myself, I have been somewhat embarrassed by the numerous physicists who have put forward very – I am looking for a polite word here – shall we say, iconoclastic, ideas about climate change. I have also noticed this personally in several occasions, that physicists have rather strong yet uninformed opinion about what climate models are good for. I am therefore happy that a physicist as well-known as Krauss counteracts the impression that physicists believe they know everything better. He 100% sticks with the established science and doesn’t put forward own speculations.
There are some topics though I wish Krauss would have said more about. One particularly glaring omission is the uncertainty in climate trend projections due to the lacking understanding of cloud formation. Indeed, Krauss says little about the shortcomings of current climate models aside from acknowledging that tipping points are difficult to predict, and nothing about the difficulties of quantifying the uncertainty. This is unfortunate, for it’s another issue that irks me when I read about climate change in newspapers or magazines. Every model has shortcomings, and when those shortcomings aren’t openly put on the table I begin to wonder if something’s being swept under the rug. You see, I’m chronically skeptical myself. Maybe it’s something to do with being a physicist after all.
I for one certainly wish there was more science in the news coverage of climate change. Yes, there are social science studies showing that facts do little to change opinions. But many people, I believe, genuinely don’t know what to think because without at least a little background knowledge it isn’t all that easy to identify mistakes in the arguments of climate change deniers. Krauss’ book is a good starting point to get that background knowledge.