When I noticed that Lawrence Krauss had published a book about climate science, I immediately bought it. Krauss is a theoretical physicist, a public intellectual and an activist who I highly respect. Over the years I have read several articles he has written.
In the Forward to The Physics of Climate Change, Lawrence Krauss gives one concrete example of the importance of thinking correctly about this issue.
...the potential impact for the Mekong Delta. During my research, I had come to realize how a confluence of factors made this region, home to sixty million people—at least fourteen million of whom depend directly on the health of the Mekong Delta—the epicenter of a Perfect Storm, where even the more conservative predictions of global climate change in the next thirty years may devastate the entire area and the lives of the people who live in it.
Krauss gives his reason for writing this book.
I am not a climate scientist. You may wonder why a particle physicist and cosmologist would wade, literally, into this subject. Because others, whose future depends on the policies governments enact and who also have to assess the discrepant claims emanating from politicians and the media, are not climate scientists either. If it isn’t possible to explain the scientific principles and predictions associated with climate change in a straightforward and accessible fashion, then what hope is there for any rational public discourse and decision-making on the subject?
I have noticed that the critics of addressing the urgency of global warming often point to the uncertainties in the climate models. But Krauss is clear-thinking on this point. It is not necessary to understand complex matters beyond the reach of average and ordinary people.
...the details of large-scale supercomputer climate models that make detailed predictions about the future are complex and intimidating, but the underlying physics governing global warming is nevertheless straightforward and grounded in basic science.
Although not a climate scientist, Krauss does have a strong connection to the subject of his book.
For over a decade, I was chairman of the Board of Sponsors of the Bulletin of the Atomic Scientists. When I joined the board in 2006, we chose to include climate change as an additional existential threat when we decided upon the setting of the famous Doomsday Clock…Later, I was fortunate to host several scientific meetings and public events on climate change. Most recently, the Origins Project Foundation I lead organized the Mekong cruise I lectured on.
CHAPTER 1 - A RIVER LIKE NO OTHER
The Mekong basin covers an area the size of France and Germany combined… All told, the river disgorges over 475 billion cubic meters of water each year into the sea, and it provides food and water for sixty million people.
...the Mekong may be one of the first casualties in the battle to head off Earth 2.0… dynamics make the Mekong Delta particularly sensitive to even small near-term changes… The Mekong Delta is a canary in a coal mine for climate change...
CHAPTER 2 - HISTORY AND NUMBERS: HALF EMPTY OR HALF FULL?
This chapter establishes several facts.
The amount of CO2 in the atmosphere is rising.
In March 1958 Keeling installed his first infrared gas analyzer at Mauna Loa, and on its first day of use, it recorded a concentration of 313 ppm. This was the first reading in what has become one of the most significant continuous terrestrial scientific projects ever carried out. It has been ongoing for the last sixty-two years and has given the world its first quantitative assessment of the impact of global industrial activity on the composition of the atmosphere.
The current levels of CO2 in the atmosphere are well beyond the range of fluctuations of the past 800,000 years as established by examining ice core data.
Krauss concludes that,
The connection between CO2 concentration in the atmosphere and the growth of human industrial production and fossil fuel appears unambiguous, making the current era qualitatively and quantitatively new in recorded human history.
Kraus identifies the next question to be confronted.
But is this quantitative change likely to be significant from the point of view of climate? That will require a discussion of the basic dynamics of CO2 on Earth, which we shall turn to next.
CHAPTER 3 - CYCLES AND CYCLES
For me, this is a more difficult chapter to understand.
Krauss identifies and explains all of the CO2 on earth - in the deep earth, the deep oceans, the surface ocean, the soil, the biosphere and the atmosphere. He explains how all this CO2 cycles and impact the CO2 levels in the atmosphere. He explains that the equilibrium established by these cycles has been disturbed.
At the current time, humanity is emitting over thirty-six billion tons of CO2 per year into the atmosphere… human industrial activity over the past sixty years has resulted in the emission of about 400 Gt of carbon into the atmosphere. That is about two-thirds as much CO2 as previously existed in the atmosphere over the past million years or so… the human footprint is anything but negligible.
CHAPTER 4 - EARTH’S BLANKET
A basic point made in this chapter was easier to understand. We all know that blankets keep us warm at night. The earth’s atmosphere is like a blanket without which the earth would be very cold.
But this chapter delivered a big surprise, that the basic science of the earth’s blanket has been known for about one hundred years. Krauss describes the work of Joseph Fourier, a scientist working in the 19th century. Fourier explained how the atmosphere captures and traps energy from the sun, but he did not anticipate current problems.
In equilibrium, Earth will radiate away into space as much radiation energy as impinges on it from the sun. Otherwise it would continue to heat up.
However, much of this chapter was quite technical. Krauss explained the significance of the different wavelengths of incoming visible light and reflected infrared light. He added relevant equations which I understood in concept but not in detail. His assertion that the basic physics of the greenhouse seems sound, but not appreciated by everyone.
This so-called “back radiation” may seem surprising, as it has been a source of confusion, especially among those who are reluctant to accept the basic physics of the greenhouse effect.
It is worth stressing that we can actually measure all of these quantities, so you don’t have to take them on faith, even if the general features are already predicted by the simplest models.
This basic picture is not controversial. What comes next depends on the details….
CHAPTER 5 - THE BIRTH OF CLIMATE CHANGE
The quantitative science underlying the greenhouse effect began with Irish physicist John Tyndall… in 1859 Tyndall began a decade-long set of experiments on the absorption of thermal radiation by different gases… His chief result was that the main gases, oxygen and nitrogen, did not have any significant absorptions, but that water vapor is the strongest absorber of infrared radiation in the atmosphere.
... Arrhenius… focused on CO2 as well as water vapor in part because Tyndall had shown that while water vapor was the dominant greenhouse gas, CO2 and some other trace gases could also have some impact.
...rising CO2 concentrations produce rising temperatures, there can be more evaporation of water, increasing the vapor content of the air, and thus further increasing infrared absorption by the atmosphere… for an increase of 50 percent in the CO2 concentration in the atmosphere, he estimated a relatively uniform increase of about 3–3.5°C, whereas for a doubling of CO2 he predicted an increase of 5–6°C… the basic framework of his results still stands today. Not bad for work done in 1896.
Enter Svante August Arrhenius, a Swedish physical chemist and Sweden’s first Nobel laureate in 1903… the first to construct an empirically derived model that allowed for the possibility of understanding how sensitive our climate may be to changes in the abundance of a molecule whose concentration in the atmosphere was less than one part in a thousand, something that without sufficient intellectual preparation, preparation, may seem absurd. For that, and the fact that the basic features of his model and the overall magnitude of his predictions remain relevant today, he certainly deserves to be remembered.
CHAPTER 6 - FORCING THE ISSUE
This chapter begins with a very useful summary of the facts established by science.
These facts led to the conclusion that the increasing CO2 concentration in our atmosphere should lead to further warming of the Earth’s surface. The key question is how much? Was Svante Arrhenius correct in estimating 3°C of warming if the CO2 concentration hits 450 ppm, which, at current rates, will occur by 2050? And even if this were true, what impact would a 3°C rise have on the globe?
Even in 1900, after Arrhenius first presented his predictions, there was almost an immediately significant academic backlash.
Krauss examines some of the early criticism of what at the time was new science. The book content again became quite technical. I was introduced to a new concept, radiative forcing.
A positive value of radiative forcing means less energy escapes from the atmosphere to space, and as a result there is a positive imbalance in incoming solar radiation versus outgoing IR radiation, which will cause the Earth’s surface temperature to rise. Radiative forcing is the most important single quantity parameterizing the response of Earth’s climate to the presence of humanity.
We have seen that doubling CO2 abundance is expected to produce slightly more than a 1 percent change in the infrared heat power absorbed by CO2 in the atmosphere.
CHAPTER 7 - BELIEVE IT OR NOT
In this chapter, Krauss turns his attention to models.
THE SIGN OF A GOOD THEORY IS WHEN MODELS BASED ON IT GET more detailed and more precise theoretical predictions based on the improved models then agree better with the data. This is the case with the original greenhouse effect, whose existence and theoretical interpretation are by now essentially unimpeachable. The physical principles behind the calculation of radiative forcing—the chief driver of climate change—are the same as those that underlie the two-hundred-year-old explanation of why the Earth’s surface is 33°C warmer than it would be without its current atmosphere.
But what should be the most striking takeaway, beyond the fact that ever-more-detailed models generally fit the data better, is the fact that the basic physics captured in even the simplest models gives answers that are consistent with the data. This suggests that they capture the fundamental physics, which is sound.
Krauss makes a distinction between the fundamental aspects of climate models and lesser, uncertain details.
The largest relative uncertainties involved the effect of clouds and aerosols in the atmosphere, while the predicted uncertainty associated with CO2 abundance was relatively small.
Once again, Krauss gets into technical details necessary for understanding his argument.
I therefore felt I owed it to you to give you the most complete and coherent general perspective I could. The physics is clear. If it isn’t to you, or still seems sketchy, blame my presentation, not the science.
Well, the physics is not as clear to me as I would like, but I do not blame Krauss. His simplification of the physics still leaves the matter beyond my full, complete comprehension. This brings me to the necessity of accepting what experts say, an important matter beyond the scope of this book report.
CHAPTER 8 - SOME LIKE IT HOT
Predicting... what might happen in the coming century is fraught with inevitable uncertainties...
...we cannot change our past, neither can we change some of the present and future consequences of humanity’s past actions.
Krauss identifies a key challenge inherent in the problem of global warming.
We often hear or read claims about our future with global warming, but these predictions range from the guaranteed to the likely, the plausible, and the possible, often with few distinctions made.
Krauss next addresses what is certain based on what has happened to date. The future does not look good as the earth will not cool down for a very long time. The graph below shows one possible scenario.
...there are two other long-term impacts that have already been written in stone: one direct and one indirect. The first impact is due to the simple thermal expansion of water as its temperature increases, a fundamental basic physics result.
The other more indirect impact that is likely to continue well after our current CO2 emission rate declines or ceases involves a predicted change in the precipitation patterns around the world with significant potential regional impacts. These are due to predicted changes in global ocean currents affected in part by differential global temperature shifts, deep mixing of heat and increased fresh-water content due to glacial melting.
CHAPTER 9 - WHAT WILL BE, WILL BE?
It is far harder to model the full complexity of daily life on Earth, much less to predict what will happen tomorrow.
As the National Academy of Sciences put it in a study published in 2011: The dynamic response of ice sheets to global warming is the largest unknown in the projections of sea level rise over the next century… there were realistically some serious risks worth worrying about.
This data make it unambiguously clear that the Greenland ice sheet is now melting at an accelerating rate, so Greenland is now contributing an ever-increasing amount to measured sea level rise… What can we expect in the long term? ...The results are sobering… The loss of the complete Greenland ice sheet would raise sea levels by about 7 meters…
Moving across the globe to Antarctica, the situation is quite different… the ice currently stored in these basin glaciers would produce 1.5 meters of sea level rise.
I have saved what may be the worst for last… we can, on the basis of the historical record, assess that a likely sea-level change on the order of meters in a few centuries is not implausible...
CHAPTER 10 - CLIMATE CHANGE TODAY
...can one find some other local evidence that a global warming signal can be clearly separated from natural variability from one year to the next? The answer is yes, at least for some locations… the issue comes down to separating signal from noise.
The first regions that therefore are already experiencing clear effects of global warming on a year-to-year basis are the equatorial and tropical regions of the world.
By the end of the century, while it will be hotter everywhere on average, in the tropics and subtropics the seasonal average summer temperature will be warmer than the warmest summer thus far almost 100 percent of the time.
CHAPTER 11 - WORST CASE: FROM FEEDBACK TO TIPPING POINTS
I was pleased to see this chapter in this book. What I have learned in recent years about chaos theory, commonly known as the butterfly effect, is troubling. It may be that that which we are least able to predict may be most important.
The problem with nonlinear feedback mechanisms is that an initial small change can produce an effect that feeds back on the changing variable, producing yet a larger effect. Pretty soon untreatably large effects can grow exponentially fast. When this happens, predictive capabilities are rapidly lost. So goes the famous example of chaos, where a butterfly flaps its wings in Kansas, ultimately causing a tornado to rip through Nebraska.
There are some important potential effects that are, however, difficult to connect directly to underlying physics or to include directly in models. This does not mean we should ignore them. One of the most powerful and important aspects of science is its acknowledgment of uncertainty.
The effects of greatest concern for climate modelers, and the rest of us, are what have become known as “tipping points”—those drastic changes, over various time frames, that once set in motion are likely to be irrevocable.
As an example, here is one scenario that the authors of the 2019 Nature opinion piece argued is already currently underway:
It will be up to decision-makers to determine if we are willing to empirically test these ideas in the coming decades. Or whether the risks, which could be small, when multiplied by the possible devastation, which in some cases could be immense, combine together to convince politicians and the public that we need to act globally now. That is, I hasten to add, if it is not already too late.
CHAPTER 12 - BACK TO THE MEKONG
Sadly, this is a battle the Mekong is destined to lose. Its demise will be swift, brought on by forces that originate from far away.
Climate change, combined with other impacts of human activity in the region, does represent a Perfect Storm closing in on the Mekong Delta. While the daily battle between the flow of one of the mightiest rivers in the world and the incoming daily tide of the China Sea goes on each day, the war has already been lost.
...the Mekong represents, in microcosm, the threat facing much of the world’s population from sea level rise.
I hope to look again at what is happening in the Mekong Delta in about ten years from now. Krauss has given us a canary in the coal mine to watch. So, let’s watch.
I hope for the sake of Cambodians and the Vietnamese, and also for hundreds of millions of Bangladeshis, Indians, Japanese, Chinese, Africans, Polynesians, Indonesians, Middle Easterners, North and South Americans, Europeans, and all the rest, that technological ingenuity combined with rational action, tempered by simple grace and empathy, might supersede our longstanding human traditions of xenophobia, greed, and violence in the face of the national and international challenges we now face. But hope and expectation are two different things.
EPILOGUE - FORTUNE FAVORS THE PREPARED MIND
I am writing this during the first global pandemic in which the interconnectedness of humanity has been manifest, and the impact of acting quickly in the face of evidence has never been clearer. I can’t say that the global report card in this regard has yet been very impressive. But I also know that most of us feel certain that this, too, shall pass.
The current nonsensical anti-vaxxers who are rabidly fighting against reality and the social contract, testify to the limitations of rationality among the human species.
Yet Louis Pasteur anticipated that when he said fortune favors the prepared mind. It makes no guarantees. It just offers better odds. I’ll take that any day.
I live in Mexico and I now have a much smaller carbon footprint than when I lived in Calgary. What more can I do? I can bring The Physics of Climate Change by Lawrence Krauss to the attention of others.