PART I — CLIMATE SCIENCE IS NOT ROCKET SCIENCE. IT IS MUCH HARDER.

Science is a process. At its best, it observes, inquires, hypothesizes, predicts, tests, measures, evaluates, and explains the reality in which we appear to live. But science is uneven. It deals with some phenomena better than others.

For instance, with exceptional accuracy, physics can determine the daily rotation of our home planet, the Earth, and its yearly orbit around our host star, the Sun. It can tell us when constellations will appear in the sky each year and when and where less frequent eclipses, both solar and lunar, will become visible and then fade from view.

Through chemistry we understand the natural elements that make up our world and the reaction of one element with one or more other elements under defined pressures and temperatures. Through chemistry we can make the steel and concrete that help us build structures for housing, education, and entertainment, and for manufacturing, distribution, and acquisition, that is, the structures that enable and define modern life.  

The world of biology is more challenging in that life forms do not operate with the regularity of planetary rotations or orbits or the interaction of chemicals under specified conditions. We can trace the past evolution of species, but we cannot predict with any certainty how they will develop in the future. We can test newly developed drugs in controlled double blind experiments involving humans in order to determine the general safety and efficacy of those drugs, but we cannot predict with certitude what, if any, adverse reactions will affect a particular individual or when.  

Compared to physics, chemistry, and biology, climate science is a relatively new science. Even at its most basic level, it deals with complex phenomena such as temperatures on Earth, both on land and in the oceans, but also in the various gaseous layers above the planetary surface to outer space itself. In contrast to a focus on short terms weather activities, climate scientists define their subject matter –– the climate –– as the average of weather over time, typically a period of thirty years. (Steven Koonin, Unsettled, 27.)

As we shall see, the temperatures we experience are the result of the interaction of numerous forces beginning with solar radiation that reaches the Earth from the Sun and including chemical and biological activity both natural and anthropogenic, i.e., human caused, within the Earth’s biosphere. Importantly, these interactions do not occur in a static system. Rather, the Earth is moving in multiple ways, on its axis and around the Sun, and this motion contributes to more motion above and below the planet’s surface in the form of wind and ocean currents. Our planet also rumbles and shifts. Volcanic activity spews chemicals into the air and alters local landscapes, while plate tectonics modify the terrain over long periods of time. In short, the subject matter that climate science seeks to understand is, as Microsoft co–founder Bill Gates has characterized it, “mind–blowingly complex.” (Gates, How to Avoid A Climate Disaster, 24.) (And if the interaction of the forces affecting the climate can blow the mind of Bill Gates, consider the challenge the rest of us face.)

About this stew of physical, chemical, and biological activity, there are some things we think we know, but much that we do not know. Part of the reason for our lack of knowledge is that we have a limited record of climate events, and much of what we do have has been compiled relatively recently. Then, too, we can neither recreate our biosphere nor run controlled experiments to see what might happen if one factor or another were altered. We can attempt to model our environment with a computer program and try to simulate scenarios, of course, but our biosphere is so large, so filled with an ever changing combination of elements and compounds, and so affected by a variety of forces both external and internal, that analyses and predictions are exceptionally difficult, as we shall also see. If rocket science is the metaphor for difficult and challenging science, then it may well be true that climate science is not rocket science –– it is much harder. So, let’s take a bit of time to look at some of what we think we know and go from there.

PART II –– SOME OF WHAT WE THINK WE KNOW.

We exist within the habitable zone of the Sun.

Earth is the third planet from the Sun, located at just the right distance from the Sun such that under certain conditions liquid water may form on the surface of the planet and biological life as we know it can emerge and thrive. In short, our home planet is located fortuitously in the habitable zone of its host star.

To understand how lucky we are, we need to appreciate a bit more about the energy that the Sun emits, the amount of that energy, our distance from the Sun, our planetary orientation to the Sun, the nature of the radiation received, and, crucially, how the Earth both absorbs and reflects the Sun’s energy.

The Sun generates energy.

Like other planets, Earth receives energy from the Sun every day and throughout the day. Astrophysicists have measured the amount of energy that the Sun radiates. According to one scientist, Ethan Siegel, that amount is 3.846 x 10²⁶ watts. And, Siegel adds, that output has not changed by more than a tenth of one percent in the time that it has been measured.

Not all planets receive the same amount of solar energy. 

The energy received by any planet depends on the distance of that planet from the Sun, and the farther out a planet is, the less radiation it will absorb. Earth is about 93,000,000 miles from the Sun. On average, about 1,361 watts–per–square–meter “hits the top of our atmosphere.” Venus, at about 67,000,000 miles from the Sun, receives considerably more power from the Sun than does Earth, and Mars, 142 million miles away from the Sun, receives much less. As we shall see, though, while distance from the host star is important, it, alone, is not determinative of the habitability of a planet.

A planet’s orbit influences the amount of energy received.

In its annual orbit around the Sun, the Earth traces a path that is more elliptical than circular. As a result, the Earth absorbs more solar energy when it is closer to the Sun and less when it is father away. Siegel tells us that the variation due to this factor is plus or minus “1.7%, with the largest amount of energy absorbed occurring in January, and the least amount occurring in early July.”

Earth’s shape, rotation, and degree of tilt matters, too.

Not only does the amount of energy change somewhat from day to day, at any one moment on any given day, Earth receives the Sun’s energy unevenly. Because the Earth is roughly round, sunlight hits it at different angles. When the Sun appears overhead, the energy Earth receives is more than when the Sun is just above the horizon. Moreover, the Earth is tilted 23.5^o on its axis, which means that a portion of the planet is more exposed to the Sun at any one moment than is another portion. The tilt also means that days are longer in some areas than others. But the Earth is also spinning on its axis, and, for the most part, but not equally, while some of the planet is receiving the Sun’s radiation another part of the planet is not.

The Earth is wrapped in a multi–layered atmospheric blanket.

The U.S. National Oceanic and Atmospheric Administration (NOAA) has identified five layers of gases which surround our planet and are collectively called our atmosphere. The layer closest to the surface of the planet, the one in which we breathe and live, the layer with most of the clouds we see and the weather we experience, is the troposphere. About seven miles up, the stratosphere begins. This is where most commercial aircraft fly. Between 31 and 50 miles above the Earth’s surface, is the mesosphere, the area where most meteors burn. The thermosphere comes next, stretching to 440 miles up. The International Space Station operates in this area. Heavily ionized, this is also where the auroras are formed. The final layer is the exosphere, which extends to 6,200 miles above the Earth’s surface. The air is so thin here that one atom or molecule could move hundreds of miles before encountering another. Many low Earth orbiting satellites can be found here.  

In addition to these five layers, the atmosphere contains two other phenomena which bear mentioning. Some would identify these as additional layers. The lower portion of the stratosphere is home to regions of ozone, a molecule consisting of three oxygen atoms.

Ozone functions to absorb or scatter a portion of the Sun’s radiation, specifically a type of ultraviolet light which can cause skin cancers and also damage crops and marine life. From the highest regions of the stratosphere, and extending to 600 miles above the Earth’s surface, the ionosphere overlaps the mesosphere, the thermosphere, and the highest layer, the exosphere. Radio communications are dependent on this region.

The chemistry of the atmosphere is unique in our solar system.

Earth’s atmosphere consists primarily of three natural elements in their gaseous state. According to the National Aeronautics and Space Administration (NASA), by volume, nitrogen (N₂), oxygen (O₂), and argon (Ar) account for about 78%, 21%, and 0.9% of the dry air in Earth’s atmosphere. The exceedingly small remnant of the atmosphere falls basically into two camps. One includes trace amounts of inert or light elements, such as neon, krypton, helium, and hydrogen. The other consists of small amounts of compounds, including principally carbon dioxide (CO₂) and methane (CH₄), but also nitrous oxide (N₂O) and synthetic fluorinated gases, including chlorofluorocarbons and hydrofluorocarbons (CFCs). By contrast, the atmosphere of Venus is almost entirely carbon dioxide and densely so, while the atmosphere of Mars is also mostly (about 95%) carbon dioxide, with some nitrogen and argon and traces of other gases, but, more importantly, quite thin.  Our planet’s atmosphere also, and uniquely,  contains important water vapor.

The Earth both absorbs and reflects solar energy.

Some of the Sun’s energy comes in the form of visible light and some in the form of invisible light, either ultraviolet or infrared. According to Ethan Siegel, on average, about 30% of the Sun’s radiation is reflected and about 70% is absorbed, a ratio that seems to be stable over time. The Earth’s reflectivity is not uniform, however, because various components of the Earth’s surface respond quite differently to the Sun’s energy. For instance, snow and ice caps reflect 80–95% of sunlight back into space, while clouds reflect about a third of the sunlight that hits them. On the other hand, forests, grassland, and corps only reflect 10–25% of the sunlight they receive. Bodies of water vary widely, depending considerably on the Sun’s altitude, i.e., its angle relative to the horizon and could reflect as little as 10% or as much as 60% of the sunlight that reaches them. Concrete reflects only 17–27% and asphalt only 5–10% of the light they receive.

Some reflected solar radiation is intercepted creating a greenhouse effect.

Not all radiation that is reflected off the Earth’s surface escapes the Earth’s atmosphere. This result occurs because different components of our atmosphere react differently to different forms of radiation. For the most part, they will allow reflected infrared radiation to pass from Earth through its atmosphere. But water vapor and nitrous oxide, as well as carbon based trace gases like carbon dioxide, methane, and CFCs will not. Instead, they create an invisible blanket that sends infrared radiation back to Earth which contributes to a warmer planet. Because of how they act and the consequences of their chemistry, these gases are known as greenhouse gases (GHGs) and the warmth they produce is called the greenhouse effect.

The insulating blanket that has surrounded our planet has been, until now, one of the great blessings for which we should be grateful. Further comparisons with Venus and Mars are instructive. Our closest neighbor towards the Sun, Venus, not only receives more sunlight than Earth does, but its dense carbon dioxide atmosphere prevents heat, in the form of infrared radiation, from escaping. Rather than simply insulating Venus, this atmosphere cooks Venus to the extent that the Venusian surface is more than hot enough to melt lead. 

Conversely, our closest planetary neighbor away from the Sun, Mars, not only receives less energy from the Sun than does Earth, but its thin carbon dioxide atmosphere, lacking reinforcing gases like water vapor or methane, is unable to capture essentially any of the radiation that is reflected off the Martian surface. It is, therefore, unable to provide much, if any, insulation for the planet and, so, the surface of Mars is largely frozen.  We’ll learn more about Mars as the latest Martian rover  digs into the red planet.

The American Chemical Society (ACS) teaches that but for the atmospheric greenhouse effect, the average temperature on Earth would be about –18 degrees Centigrade or 0^o Fahrenheit. Only because the average temperature has been much higher for billions of years, has life on Earth been able to evolve the way it has. For the last few thousand years, that average temperature has been about 15 °C or 59 °F. (Accord, Koonin, at 48–49.)

Greenhouse gases differ in their impact and longevity.

The primary atmospheric gas which re–reflects infrared radiation back to Earth is water vapor, a non–carbon based GHG. Steven Koonin, a physicist and, among other things, a former Under Secretary for Science in the Department of Energy during the Obama administration, asserts that water vapor, although “only about 0.4 percent of the molecules in the atmosphere” nevertheless “accounts for more than 90 percent of the atmosphere’s ability to intercept heat.” (Koonin, at 51.) NASA attributes 50% of the greenhouse effect to water vapor and about 25% to clouds. Regardless of the degree of its dominance, among GHGs, water vapor is also unique in at least three consequential respects: the “amount in the atmosphere at any given place and time varies greatly” (Koonin, at 50), the overall amount of water vapor in the atmosphere does not change much, and, as Siegel advises, there is nothing that humans can do that can have “any impact on the amount of H₂O in the atmosphere.”   

The second most important GHG, according to Koonin, is carbon dioxide which accounts for “about 7 per cent of the atmosphere’s ability to intercept heat.” (Koonin, at 51.) Carbon dioxide occurs naturally due to human and other animal respiration (we exhale it) and volcanic eruptions. The amount of CO₂ humans produce by breathing, however, does not result in a net addition of CO₂ to the atmosphere, but volcanic activity does. At the same time, humans also contribute to additional CO₂ release through numerous activities in the manufacture, distribution, and use of goods and services, about which more below. And the amount of CO₂ added to the atmosphere annually by such activities is, perhaps, sixty times the amount contributed by volcanoes.

As a GHG, carbon dioxide differs from water vapor in two important ways. First, its concentration around the globe is similar. (Koonin, at 33.) Second, while some carbon dioxide may be absorbed quickly, the U.S. Environmental Protection Agency (EPA) tells us that some molecules of the compound may also last for thousands of years. NASA’s estimate is that the potential life of CO₂ is between 300 to 1,000 years. Not to diminish the different evaluations, but both agree that CO₂ lingers.

Other gaseous compounds that make up just a tiny percentage of our atmosphere also play major roles in trapping Earth’s radiant heat and keeping it from escaping into space, thereby warming our planet. Methane is also produced naturally, for instance, when cows expel gas, and through human activity involving, among other things, waste management and agriculture. According to the EPA, CH₄ can last over 12 years in our atmosphere. Chlorofluorocarbons are used in a number of applications including in aerosol sprays and as solvents and refrigerants. CFCs may dissipate in a few weeks, but may also survive for thousands of years.  Nitrous oxide is a non–carbon based GHG, the byproduct of soil cultivation processes and wastewater treatment operations. Nitrous oxide can remain in the atmosphere for over a century.   

Long lived GHGs are increasing in our atmosphere.

Scientists have studied the presence of long lived greenhouse gases using two principal methods. One involves analyzing ice cores to determine conditions as far back as 800,000 years and, more recently, taking direct atmospheric temperatures. These studies confirm changes in the concentration of these gases over time and support three critical conclusions: 

1. Since 1750, just prior to the start of the industrial revolution, “atmospheric concentrations of CO₂, CH₄, and N₂O . . . have increased substantially.”
2. Focusing on carbon dioxide, we find that while levels of atmospheric C0₂ has risen and fallen over extended periods of time, at no time prior to 1950 did the level exceed 300 parts per million. It passed that level around 1950 and then passed 400 parts per million in 2013. The most recent monthly measurement, taken in May, 2021 at the Mauna Loa Observatory in Hawaii, recorded a CO₂ concentration of over 419 ppm, some perhaps attributable to seasonality, but, still, even greater than the new record set in 2020 for the past 3.6 million years.
3. The rate of increase is also increasing. “CO₂, for instance, never increased more than 30 ppm during any previous 1,000-year period in this record but hasalready risen by 30 ppm in the past two decades.”

Various  human activities are emitting different GHGs into the atmosphere in different ways.

For many of us, perhaps for all of us other than chemists, measurements in parts per million are not readily comprehensible. And, in any case, the difference between 280 ppm and 419 ppm is only 139 parts per million, which may seem trivial. There is another approach to what is going on with our atmosphere that may be more helpful and that is to consider the amount of greenhouse gases added annually by human activity worldwide to the atmosphere. According to Breakthrough Energy, a business group chaired by Bill Gates, that amount in recent years approximates 51 billion tons. While it is also difficult for most of us to imagine one ton of gas, 51,000,000,000 tons does seems like a lot.  

What is also vitally important to understand is the nature of the activities that generate these greenhouse gases. In his recent book, How To Avoid a Climate Disaster, Gates identifies five main activities and the percentage of their annual worldwide contribution of greenhouse gases: making things (31%), growing things (19%), transporting things (16%), and heating and cooling (7%), plus generating, distributing, and using the electricity which makes possible much of the first four activities (27%). (Gates, at 55.) Using somewhat different definitions for the various economic sectors, and focusing solely on the United States, the EPA has found that (as of 2019) the following activities produce the percentages of GHGs indicated: transportation (29%), electricity (25%), industry (23%), commercial and residential buildings (13%), and agriculture (10%). The differences between the worldwide numbers and those based solely on United States activity underscore that the economic activity, and status, of different nations is not uniform.

Among the many examples that Gates provides, there are a few which illustrate both the diversity of contributors of greenhouse gases and the complexity of the challenge to contain or even reduce such emissions. The first two examples are selected not only because the products and their applications are ubiquitous, but also because the United States is currently considering increased investments in infrastructure in which will involve significant amounts both of these products. The products are steel and concrete.

Essentially, steel is made by melting iron ore, which contains some oxygen, with free oxygen and coke, a high carbon byproduct of coal. Some of the carbon in the coke binds with iron from the ore and produces steel. Some of the carbon binds with the oxygen from the ore and creates carbon dioxide. Gates says that “(m)aking 1 ton of steel produces about 1.8 tons of carbon dioxide.” (Gates, at 103.)

Making concrete is also a relatively simple process, being the combination of gravel, sand, and water, plus cement. To get cement, though, you have to burn limestone, itself made of calcium, carbon, and oxygen. At the end of the process, you will get the desired calcium, but also undesired carbon dioxide. Gates reminds us that the chemistry is inexorable and direct: “Make a ton of cement, and you’ll get a ton of carbon dioxide.” (Gates, at 104.)

The third example comes from what Gates characterizes (at 118) as “pooping, burping, and farting,” understandable, if neither technical nor elegant terms for the common consequences of animal digestive practices. In cattle and other ruminants, the digestive process is enteric fermentation in which bacteria reduce plant cellulose, ferment it, and yield methane. The bottom line, so to speak, is that about a billion cattle around the world annually expel methane from one end or the other that collectively “has the same warming effect as 2 billion ton of carbon dioxide, accounting for about 4 percent of all global emissions.” (Gates, at 117.) And fermented gas is not the only issue. When agricultural animals, primarily pigs and cattle, poop, the decomposing poop “releases a mix of powerful greenhouse gases––mostly nitrous oxide, plus some methane, sulfur, and ammonia.” (Gates, at 117.)

There is evidence of global warming, but it requires context.

If greenhouse gases can contribute to global warming by trapping solar radiation and if there has been a dramatic, even unprecedented, increase in such gases measured in relatively recent years, then, all else been equal and  depending on how quickly the additional GHGs affect temperatures, one might expect to see evidence of such warming. Is there such evidence?

NASA asserts that the best evidence accumulated to date indicates that we are in a period of global warming.  The evidence comes from a variety of sources and is derived from measurements of land surface, ocean, and atmospheric temperatures. According to NASA, the average land surface temperature has increased about 2.12 degrees Fahrenheit since the late nineteenth century. It also asserts that warming has increased in the last forty years, with the years 2016 and 2020 being the warmest recorded.  Koonin confirms that “(w)e can all agree the globe has gotten warmer over the past several decades” (Koonin, at 100), but notes that a close look at the data discloses more frequent record high temperatures in the 1930s (in the U.S.) and suggests that the rise in temperatures overall is attributable to a decline in the coldest temperatures. (See Koonin, at 100–110.)

More specifically, as an example of the consequences of global warming, NASA reports that hundreds of billions of tons of ice from ice sheets in Greenland and Antarctica have melted away in the last decade, and that the rate of ice mass loss has increased during that time.  It also says that seas levels have risen about eight inches over the course of the last century and the rate of rise over the last two decades has almost doubled. Koonin does not address the tonnage issue directly, but notes that as the globe warms, sea levels rise, land ice melts, and “as oceans warm, the water in them expands.” (Koonin, at 159.) He does, however, take issue with the implication of the reporting of the increase in sea levels in recent decades. He does so because the data show that global mean sea levels have fluctuated considerably during the previous century and that the recent increase is not much greater than the increase between 1925 and 1960, well before the recent acceleration in global warming. (See Koonin, at 154–59.)

PART III – SOME OF WHAT WE DO NOT KNOW WELL OR AT ALL.

As you have read, we think we know quite a bit about global warming, the forces which bring it about, and the human activity that unnaturally emits chemicals into a vulnerable atmosphere. Does this mean that the science is clear and settled, that we have a consensus about global warming and climate change? Not exactly. For starters, “the science” is too broad and too vague a term and, in any case, science is an ongoing process or methodology which, by nature, is not settled.

More importantly, the hard truth is there are many uncertainties attendant to that which we think we know, there is a great deal that know we do not know, and, undoubtedly, there is also a lot that we do not realize we do not know. The subject matter of our lack of knowledge is vast, encompassing not just the causation and impact of our present circumstances, but the potential difficulties we face as we anticipate the future, not just theoretically, but from a technological, social, political and economic vantages points. Again, if we want to discuss this serious topic seriously, we need to understand the limits of our knowledge. Let’s consider just three kinds of these challenges: one substantive, one technological, and one methodological.

Substantive knowledge challenges.

Some substantive knowledge gaps are narrow, while others are broad. Some relate to the present, while others concern the future. Here is a small sample:

1. Though the summer of 2021 has just begun, the western portion of the United States has been submerged under an oppressive heat wave, one resulting in record hot temperatures, especially in the Pacific Northwest. While we know the Earth’s surface temperature is rising generally, and that atmospheric high pressure systems can cause heat waves, our knowledge of what produces the high pressure systems in the first place is “rudimentary.”
2. Feedback processes are those that can increase or decrease the effect of growing concentrations of GHGs. These processes are “dominated by cloud formation, but also include water vapour and ice feedbacks, ocean circulation changes, and natural cycles of greenhouse gases” and they are “uncertain.” More specifically, say researchers from Princeton, “it is not yet clear whether changes in cloud properties will further amplify or dampen the GHGs induced warming, or by how much. Uncertainties in predicting this radiative feedback from clouds are the largest cause of spread in model predictions of future global warming  .  .  .  .”
3. Then there are the troubling known unknowns of the future, which include, according to Dr. William B. Gail, a past president of the American Meteorological Society, “how much Earth will eventually warm, how rapidly oceans will rise, where and when weather extremes and water shortages might occur, and whether potential tipping points (like the collapse of Antarctic ice sheets) will, in fact, occur.”
4. Worse, for our attempt to understand this subject, are the unknown unknowns. Says Dr. Gail, “What will actually emerge is largely unknowable because of the highly unpredictable nonlinear response to the warming of Earth’s complex and adaptive physical and ecological systems.”
5. Given the significant uncertainties of our present knowledge, though politicians and the press, among others, will often be quick to do so, as Bill Gates has recognized, we cannot, “with certainty blame climate change for any particular event.” For instance, “it’s unclear whether warmer oceans are causing a rise in the number of” hurricanes. (Gates, at 25.) 
6. Although humans have been among the most adaptable of life forms on our planet, we do not know how we will adapt to a warming globe and resulting changes in our local environments.
7. Global cooperation will be vital to any effort to reduce GFGs. As Bill Gates reminds us, though, achieving “(g)lobal cooperation is notoriously difficult.” (Gates, at 50.) How can we predict the nature or extent of such cooperation? Past models did not include events such as Brexit, an American administration that would withdraw from environmental accords, or trade wars with and among various countries. How can future models deal better with such unknowns?

Technological challenges.

In his book, Bill Gates spends relatively little time on the science underlying global warming and projections for the future. (See Gates, at 21–25.) Nevertheless, he argues that “(u)nless we stop adding greenhouse gases to the atmosphere, the temperature will keep going up,” that “at some point the impact will be catastrophic,” and “(t)o avoid a climate disaster, we have to get to zero” emissions of GHGs. (Gates, at 8, 25.) Even assuming that Gates’s fears are justified, even assuming that we wanted to get from here to there, to be carbon neutral by 2050, we don’t know how to do it and we cannot predict whether the new technologies we will need will be developed and, if so, by when.

Gates concedes that to achieve carbon neutrality within thirty years, in addition to deploying today’s technologies more widely and wisely, we will need to “create and roll out breakthrough technologies . . . .” (Gates, at 8.) What are these? Among the many he discusses are a national electric grid that is cheap and reliable, underground electricity transmission, zero–carbon cement, zero–carbon steel, zero carbon fertilizer, drought and flood tolerant food crops, coolants without CFC gases, next generation nuclear fission, and hydrogen produced without emitting carbon.

Now just consider one of these problems for a moment. Recalling the troubles in California, Texas, and the Pacific Northwest in recent years with respect to electricity transmission, can you imagine the technological and political challenge in developing a national grid system? Can you imagine the challenge in developing any electrical system that is not only reliable and affordable under extended as well as normal operating conditions, but can also withstand repeated attacks from terrorists and computer hackers?

Methodological challenges.

If there are serious gaps in our knowledge of present global warming, of as yet undeveloped technologies, and of unforeseeable political activities, what can we say about the future? Unlike many areas of scientific inquiry in which the standard methodology includes testing of hypothesis in a laboratory or under controlled field conditions, climate science depends on modeling. That is, climate scientists create “computer programs that perform mathematical simulations of the climate system.” (Koonin, at 77.) But “usefully describing the earth’s climate remains one of the most challenging scientific simulations problems there is.” (Koonin, at 78.)

Typically, the atmosphere is divided into three dimensional grids resulting in millions of grid boxes, the current state of the ocean and atmosphere at a particular time and natural is then specified, and many and various assumptions are made about natural and human influences on the climate in each grid box. (Koonin, at 79–83.) Then the model will be adjusted or “tuned” in an attempt to compensate for perceived errors in the model and better reflect the realities of the current climate. (Koonin, at 84–86.)

All along the way, choices and compromises are made without complete or even adequate knowledge. In addition to the subjects mentioned above, another important area of concern is large scale patterns of precipitation where models “’continue to perform less well . . . than for surface temperature.’” (See Koonin, at 145.) Yet another concerns aerosols. We know that aerosols exert a cooling influence and, to some degree, mitigate GHG warming. How modelers should treat aerosol interactions with clouds, which themselves come and go, is not clear. (Koonin, at 93–94.) And, of course, there is the “computational challenge of simulations that can take months to run on even the world’s fastest computers . . . .” (Koonin, at 95.) And how do you even attempt to model the as yet undeveloped technology of the future that may make current assumptions and extrapolations meaningless? Or the political will necessary to effect changes?

Gates, who knows something about computer programs, concludes that “computer models are far from perfect.” (Gates, at 24.) This conclusion is buttressed by the fact that models yield a wide range of results. (See Koonin, at 86–91.)  Still, that climate models are flawed does not mean that they are not useful. Clearly they are. Even more, the reality is that we have no choice but to look to models in order to understand the complex phenomenon of global warming and possible scenarios we may face in the future. Still, the inherent complexity and the imperfections and limitations of modeling should stand as cautionary reminders that there are limits to our understanding, and, further, suggest that those who look to models for guidance when assessing the relative benefits and detriments of possible courses of action do so with care. 

***

Given what we know, what we do not know well, if at all, and allowing for unknown unknowns, what can we say about the human contribution to global warming? The reasonable scientific inference would seem to be that human activity is responsible to some degree for global warming. Ethan Siegel says simply: “The Earth is warming, and humans are the cause.” 

Can we assign better the degree to which humans are responsible? NASA, without disclosing its methodology or mathematics, places the likelihood of human causation at “extremely likely,” meaning greater than a 95% probability. 

But are these the right questions? Steven Koonin, while not disputing the fact of global warming or human contribution to it, asks about the impact of human conduct, the “extent this warming is being caused by humans.” (Koonin, at 44.) For instance, he says that “(t)here is little doubt that by contributing to warming we have contributed to see level rise,” but, having reviewed the long-term natural cycles and various local factors, adds, “there’s also scant evidence that this contribution has been or will be significant, much less disastrous.” (Koonin, at 165.)

Here Koonin is clearly in the minority, but good science does not depend on votes (ask Galileo) and, in any case, Koonin is not alone. Emeritus Professors Richard Lindzen of MIT and William Harper of Princeton recently took a similar stand. They, too, agree that the infusion of more carbon dioxide in the air “is likely to cause some surface warming.” They argue, however, that “the warming would be small and benign.”

We will not resolve here the difficult questions attendant to the complex study known as climate science. Our immediate concern is different. Given what we think we know, what we do not know well, if at all, and allowing for the unknown unknowns, can Judaism say anything credibly and productively about climate science generally or global warming more specifically? We will address that question in the next post.

1. Bob Magrisso says:

   July 13, 2021 at 4:50 pm

   Great review of the background and fundamentals of climate science and he knowns and unknows that it faces:  so many variables interacting in nonlinear ways and not too much in the way of controlled experiments.  I have faith that models have and will get better over time but time seems be going against us if we are to have any significant effect on the climate.  It seems that we are in a situation where actions are necessary but coordinated actions by large groups of humans cooperating seems beyond our reach.  I look forward to the next chapter!  I expect nothing less than Talmudic wisdom.  

    

   Reply
2. Jonathan H Spinner says:

   July 21, 2021 at 7:56 am

   I appreciate your hard work in explaining some of the science behind climate change, but scientists as far back as von Humboldt have warned that human activities could result in climate change (he used just this term in his book "Kosmos," published in 1800), so it is not a new concern. I will be interested in your injection of Jewish thought into climate change — like CO2, Jewish thought raises the temperature!

    

   Reply