Jun 11, 2021

An (actual) explanation of climate change.

An (actual) explanation of climate change.

We're doing something a little different.

I’m Isaac Saul, and this is Tangle: an independent, ad-free, subscriber-supported politics newsletter that summarizes the best arguments from across the political spectrum — then “my take.” This is a special Friday edition. If someone forwarded you this email, or you found this online, it’s a sign you should subscribe.

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This read: 15 minutes.

One of the most common refrains on the topic of climate change is that it “shouldn’t be a political issue.”

The reason for that, in many people’s eyes, is that it’s purely a scientific issue. Ideally, this ought to be true. The snag is that addressing climate change is a deeply political issue — it’s something that will almost certainly require human action, government intervention, private sector buy-in, and efforts from the global citizenry as a whole. In many cases, it could involve actual lifestyle changes.

Whether you view climate change as a political issue or not is actually irrelevant, because it has become one. That means, as a political journalist, I’ve had to cover it.

Over the course of my career as a reporter, I’ve actually done quite a bit of work on climate change. I’ve reported on the band of teenagers who sued the U.S. government for its role in allowing climate change, which they argued was an infringement on their liberty. I’ve reported on dozens of pieces of climate change legislation. I’ve reported on candidates — from presidential to local levels — who decided to run on a climate change platform (and how it impacted their races). And I’ve also reported on the climate change skeptics: the politicians, pundits, political donors and energy executives who have argued that the threat of climate change is being vastly overstated by the left.

Photo by Dorothe form PxHere

I’m not a dogmatic person. I’ve changed my mind about all sorts of critical issues over the years, from gun control to the existence of God to UFOs to how to solve our broken immigration crisis. I’ve changed my mind about politicians like Barack Obama and moved my position on hot-button issues like critical race theory. I say this all to note that I’m open: I enjoy being wrong. I find it exhilarating and terrible and fun and ultimately it has always helped me grow.

And in all this time reporting on this issue, learning about it, engaging with a wide range of views, my perspective has really not moved much. I believe we are witnessing a period of time where humans are causing the Earth to warm; I believe that warming will have catastrophic impacts on the planet that will probably fall to our grandchildren but that we are beginning to witness now; I believe that the issue is complex, but that the science can be easy to follow. I also believe this will be a defining issue — politically, scientifically and globally, in everyday life — for the next 100 years.

Today’s edition is not about the politics of climate change. It’s not about what we should do to address it, or what pieces of legislation are best, or which party is in denial. Instead, as a staff, and with the consultation of climatologists, we’re just going to try to give you a thorough understanding of the scientific issues at hand. We’re going to do something far too few news outlets have done: explain what’s happening, what the science says, what the skeptics say, what we can reasonably infer from all of this, and what we don’t actually know yet.

And since this piece is covering a scientific issue, I collaborated more with the Tangle staff — and outside sources — than I usually do. A few months ago, we added an editor named Ari Weitzman to the team; you may remember that he pushed me to write about American Indian Reservations and supplied the introduction in a previous Friday edition. He also happens to have a degree in Environmental Studies from the University of Chicago and a deep interest in climate change. I’d like to thank him, because he did the bulk of the research and prep work for today’s edition: I’ve worked with him to try to make it easier to read, understand, and flesh out the most important points. I’ve also given him a byline on this piece for his work, which is the first time I’ve ever shared a byline in Tangle (we’re growing!).

Since this is a unique edition of Tangle, I’m especially interested in your feedback. And as a reminder, you can always reply to this email to reach me or, if you’re a subscriber, you can leave a comment on the article by clicking the headline of this piece in your email or going to our website, https://www.readtangle.com/

Finally, I encourage you to share today’s piece if you feel inclined. I have made it available to all Tangle readers.

Some basics.

Joseph Fourier was a French mathematician who lived from 1786 to 1830. He isn’t very renowned today, except by scientists and mathematicians. Like many great thinkers, he has a namesake work: Fourier Analysis, which falls under a branch of mathematics called harmonics. However, part of Fourier’s most significant work was his study of heat and conduction.

In 1824, Fourier wondered about the Earth’s temperature. After conducting a rudimentary analysis, he concluded that the Earth was warmer than it should be given that its only heat source is the sun. Fourier theorized that something must be insulating the planet to prevent heat from the sun from radiating back into space, and proposed that gases in our atmosphere trap and radiate heat back to the surface.

Over the coming century researchers would reaffirm this theory, and today we know this concept as something called the greenhouse effect.

It’s actually a rather simple idea: The Earth’s atmosphere allows most direct sunlight through, where it is absorbed by the planet and re-emitted back as heat energy. Imagine a strip of asphalt in direct sunlight. When you stand over it, you can feel the heat emanating from the surface. On a planetary scale the Earth is doing the same thing, and some surfaces like exposed rock and asphalt radiate more heat than others like plant cover or ice sheets. A portion of that heat is then insulated by the atmosphere, and reradiated back to the surface. This is a natural process that allows Earth to retain energy from the sun, and regulate its temperature.

We call the gases in our atmosphere that insulate this heat “greenhouse gases.” Here is the technical definition from the National Oceanic and Atmospheric Administration (NOAA):

“Many chemical compounds present in Earth's atmosphere behave as 'greenhouse gases'. These are gases which allow direct sunlight (relative shortwave energy) to reach the Earth's surface unimpeded. As the shortwave energy (that in the visible and ultraviolet portion of the spectra) heats the surface, longer-wave (infrared) energy (heat) is reradiated to the atmosphere. Greenhouse gases absorb this energy, thereby allowing less heat to escape back to space, and 'trapping' it in the lower atmosphere.”

In other words: greenhouse gases are those that let sunlight (and its energy) through, but then stop that energy and heat from going back into space.

These gases include water vapor, carbon dioxide, methane, nitrous oxide, and fluorinated gases. The EPA’s website is an informative source of information on the wide variations in the energy absorption strength, lifespans in the atmosphere, and sources of all of these gases. Fluorinated gases are very powerful greenhouse gases and can live in the atmosphere for up to 270 years, but they aren’t naturally produced and are emitted from human activities (primarily as aerosols and refrigerants) at a much lower rate than other greenhouse gases. Conversely, carbon dioxide is a much less powerful greenhouse gas, but is produced both through natural process and human activity, and at a much higher rate.

In the United States, carbon dioxide emissions are roughly five times larger by volume than emissions of all other greenhouse gases combined. Carbon dioxide is also a part of what’s called the global carbon cycle, which we’ll explain in more detail in a second. Generally, the carbon cycle is a process where geochemical and biological events play a role in how carbon dioxide is processed (like, say, by being absorbed into the ocean). This means some excess carbon dioxide will be naturally processed by the planet, while some will remain in the atmosphere for thousands of years.

The carbon cycle.

Even though it’s a “less powerful” greenhouse gas, carbon dioxide gets a lot of attention because of the length of time it remains in the atmosphere and the huge volume at which humans emit it. Primarily, climatologists are concerned with carbon dioxide in relation to the atmosphere’s greenhouse effect. As its name suggests, CO2 is a molecule composed of one carbon atom and two oxygen atoms. As with methane (CH4: one carbon atom and four hydrogen atoms), a more powerful greenhouse gas that is emitted at a much lower rate and lives on in the atmosphere for about a decade, carbon dioxide contains carbon.

One thing you’ll often hear from people skeptical of the threat of climate change is that carbon dioxide is a naturally occurring component of life on Earth. This is the kind of challenge that is both true and misleading: it’s true that carbon dioxide is natural and critical to life. It’s misleading to suggest that means everything is fine if we’re emitting additional millions of tons of it into the atmosphere every year.

As NASA writes, “Carbon is the backbone of life on Earth. We are made of carbon, we eat carbon, and our civilizations—our economies, our homes, our means of transport—are built on carbon.” Carbon exists naturally in the landmasses of the Earth, the ocean, and the atmosphere. It is also naturally exchanged through these three reservoirs in a process known as the carbon cycle. Over hundreds of millions of years, the balance of carbon in these reservoirs may vary, but the geologic (i.e. occurring over a time scale of millions of years) exchange between them has remained relatively consistent over time. In fact, for the 50 million years prior to 1890, carbon dioxide levels in the atmosphere were dropping, and the planet — with some periodic fluctuations — was cooling.

Again: this is an accurate point often made by people skeptical of the dangers of climate change, interpreting real science to come to a misleadingly comfortable position of unconcern (of course, it’s also worth pointing out the obvious: The scientists who are telling us the world has been cooling on a geological scale are also the ones sounding the alarms about climate change).

Still, as more and more carbon has been released into the atmosphere since the start of the industrial revolution, the carbon cycle has seen one noteworthy change: the exchange of carbon between the ocean and atmosphere has tipped towards the ocean absorbing much more carbon than it is releasing. On one hand, the ocean absorbing as much as a third of global carbon has provided a regulating effect on heating and has prevented extreme warming from occurring over the last 100 years. On the other hand, for the health of ocean life, it’s extremely bad. One of the ways we know that the ocean is absorbing carbon is that it’s acidifying, significantly. From NOAA again:

Carbon dioxide, which is naturally in the atmosphere, dissolves into seawater. Water and carbon dioxide combine to form carbonic acid (H2CO3), a weak acid that breaks (or “dissociates”) into hydrogen ions (H+) and bicarbonate ions (HCO3-).

Because of human-driven increased levels of carbon dioxide in the atmosphere, there is more CO2 dissolving into the ocean. The ocean’s average pH is now around 8.1, which is basic (or alkaline), but as the ocean continues to absorb more CO2, the pH decreases and the ocean becomes more acidic.

Global warming.

The interplay between the greenhouse effect, the lifespan of carbon dioxide in the atmosphere, and the carbon cycle presents a basis for the theory of human-caused (or anthropogenic) global warming. As early as 1896, the Swedish scientist Svante Arrhenius suggested that the global trend of fossil fuel combustion would result in a warming Earth.

Once again, the theory is fairly direct: more fossil fuels burned means more carbon dioxide released into the atmosphere. The more carbon dioxide in the atmosphere, the longer it takes the natural carbon cycle to transfer the carbon to the land and ocean, and so it accumulates. The accumulating carbon dioxide enhances the greenhouse effect and results in more heat being contained by the atmosphere. This drives global mean temperatures higher.

It would take some time for Arrhenius to be proven right. Due to Earth (at a geological scale) being in a cooling phase, the planet’s natural capability for self-regulation, and the sheer magnitude of the process of global climate change, our planet’s global mean temperature would not be observed to dramatically curve upwards until the 1980s. In 1988, The New York Times reported that “temperatures have been rising more or less steadily for much of the last century. But, in the view of some scientists, a sharper rise detected in the 1980s is the most persuasive evidence yet that carbon dioxide and other industrial gases are trapping heat in the atmosphere and warming the earth as if it were a greenhouse.”

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The support for anthropogenic factors causing global warming requires data on a large scale — which we have. One of the most iconic visualizations of such data has come from Charles David Keeling’s observations at the Mauna Loa Observatory in Hawaii, which he began making in 1958 and whose observatory is still gathering data to this day. The Keeling Curve, as it’s widely known, is a chart that demonstrates the increase of atmospheric concentration of carbon over time. It looks like this:

Since 1958, carbon dioxide concentration in the atmosphere has increased from 320 parts per million (ppm is on the Y-axis in the above chart) to 420 ppm. The Keeling Curve also demonstrates annual seasonal variability of atmospheric carbon, which had previously only been theorized. Since the large majority of plant life on Earth is in the northern hemisphere, plants will be “breathing” more in the summer — emitting more oxygen and absorbing more CO2. See how the curve on the graph has a jagged, saw-tooth pattern? That pattern confirmed the seasonal variability theory to scientists, and that expected pattern reinforces the reliability of the data from Mauna Loa.

Further, with recent advances in technology, we have been able to accurately read carbon concentrations in the atmosphere through studying samples called ice cores retrieved from ice sheets and glaciers. When we take the Mauna Loa observations and append them to the hundreds of thousands of years of ice core data, the atmospheric concentration of carbon over time looks like this:

The data speaks for itself. And given what it shows us, it appears impossible to refute Arrhenius’s theory that human beings have measurably increased the concentration of carbon dioxide in the atmosphere.

As we’d expect, given this concentration of carbon dioxide, Earth’s global mean temperature has been increasing for over a century, with a particularly sharp increase in the 1980’s. Geologically, however, Earth is far from the hottest it has ever been, which is demonstrated in this chart:

Without ice core data to extend back hundreds of millions of years ago, when the Earth was so hot that there were no glaciers or ice caps, it is hard to get an accurate understanding of the level of carbon in the atmosphere at that time. Through a new methodology that uses seismic tomography, however, scientists in the Netherlands believe that the carbon dioxide concentration was about twice as much as it is today — which supports the understanding that atmospheric carbon drives global temperatures.

Additionally, it is important to think about the scale represented in the temperature graph above. The entirety of the ice core data we have corresponds to the extreme right-hand portion of the chart — the part above the letter “y” in the word “Today” on the x-axis. The wide fluctuations in global temperature shown above to have occured over thousands to millions of years are due to a combination of complex factors. Over a period of a hundred years, however, an increase of a few degrees Fahrenheit sticks out. It is notable, and likely due to a singular cause. During one such major increase marked above, the Paleocene Eocene Thermal Maximum (PETM), a massive atmospheric carbon spike accompanied an observed acidification of the ocean, again reinforcing our understanding of the carbon cycle and temperatures.

The causal relationship between atmospheric carbon and temperature increase that was theorized in 1896 and demonstrated during the PETM is being demonstrated again now. Since atmospheric carbon began increasing in 1880, global mean temperatures have risen over a degree Celsius (about 1.4 degrees Fahrenheit).


The data indicate a clear trend in increasing temperatures starting in the 1980s and continuing to this day. Since climate change theorists have long understood the connection between carbon dioxide and global temperature, there has been no shortage of models that have attempted to forecast future temperatures. One good way to challenge the anthropogenic warming theory, and evaluate if it is correct, is to look at the performance of the models that assume human-caused warming. In a metastudy performed by NASA that evaluated 17 warming models from 1970 to 2007, the research team found that 14 fit observed data, with 10 “closely matching observations.”

And what are models forecasting now? Current warming will create future warming.

This forecasted increase is due to a process called a positive feedback loop, which is a process whose outputs increase its inputs, thereby causing the process to accelerate. Positive feedback loops can happen in different ways, but here are a few concerning ones that we’ve already observed:

  • More heat means a higher concentration of water vapor can be trapped in the atmosphere. Water vapor is a greenhouse gas, which means more warming, which means more water vapor in the atmosphere.
  • The ice caps and glaciers reflect sunlight back into space, so it can’t be absorbed and reradiated back as infrared light to be trapped by the gases in our atmosphere. This helps keep the planet cool. But as global temperatures get warmer, the ice caps melt, meaning less sunlight is reflected back... which means more sunlight is absorbed and radiated as heat, which means more melting.
  • Methane and carbon dioxide are trapped in permafrost — soil that remains frozen all year round. There is a lot of carbon stored in permafrost in the Siberian and Canadian tundras, for example. Higher temperatures mean melting permafrost, which means more carbon released into the atmosphere, which means more permafrost melting even faster.

It isn’t all bad news, though. There are actually a few negative feedback loops, too, all of which are projected to help regulate the warming process.

  • Warming means more evaporation, which means more cloud cover. Clouds reflect sunlight back into space, which decreases warming.
  • The hotter the earth gets, the faster it radiates heat out to space. The faster heat is lost by the planet, the more slowly its warming occurs.
  • Human behavior causes emissions that cause warming, which humans notice and use to evaluate their own behavior. This evaluation causes less emissions… we hope.

In general, scientific models are projecting a two-to-five degree celsius increase in global mean temperatures between now and 2100. The largest unknown factors are the natural variations in Earth’s carbon cycle and how much intervention humans will be able and willing to take. However, due to the positive feedback loops that have already started, even extreme intervention is not likely to be enough to prevent some warming.

To put it another way, warming itself is a cause of warming. If our actions are left unchecked and we go about “business-as-usual,” the effects of warming will themselves be the leading cause of warming; at which point it will be too late for action. If those feedback loops become self-sustaining, there will be little we can do to prevent a “Hothouse Earth” and the resulting catastrophic effects.

Climate change.

“Global warming” is the general understanding that the Earth is getting hotter, and the implication and informed consensus is that human activity is driving that increase. “Climate change” refers to all the other effects, like the ocean acidification described above, that the global mean temperature increase will cause. These effects include changes in precipitation patterns, more droughts and heatwaves, a longer growing season, stronger hurricanes, and drastic sea level rise.

“Climate change” is mostly used as an umbrella term to refer to any changes to Earth’s climate that are caused primarily by the increase of atmospheric carbon from human beings, but the science behind it is based primarily on the understanding of anthropogenic warming.

Part of understanding climate change is grasping the magnitude and consequences of the climate’s changes to all life on Earth. The Earth itself has gone through hot phases before, and life on Earth will find a way to continue. However, biodiversity and stable environments, factors that human life on Earth depend on, will be greatly stressed. In fact, based on the warming we’ve already experienced, biodiversity is already being stressed. And since the planet has never experienced warming this quickly before, we don’t really know how such a sudden change to global climate will continue to affect life on Earth.

We know it won’t be a good thing, though. According to the journal Health Affairs, should temperatures increase by 1.5°C, a United Nations Intergovernmental Panel on Climate Change (IPCC) report found that “of 105,000 species studied, four percent of vertebrates, six percent of insects and eight percent of plants would lose half of their climatically-determined geographic range. At 2°C the percents double to triple. At 1.5°C we will lose 70 to 90 percent of coral reefs, at 2°C there will be a 99 percent loss.” This will mean loss of habitable and arable land, which in turn mean mass migrations and decreased food production, which in turn mean human death and catastrophe at a scale that is hard to predict or imagine.


There has been doubt and skepticism leveled against climate change and global warming for as long as the terms have existed. Criticism over forecasting models and their performances have generally been in good faith, but theoretical criticisms of climate change are in many ways not much more reasonable than challenging Earth’s roundness. We actually have a very good understanding of what’s going on. And, as it happens, many of the loudest, most well-funded skeptics of climate change have either reversed course or been outed for pushing propaganda in order to boost their own profits (see: executives in the energy industries and the politicians they bankroll).

Some of the most popular skeptic responses are as follows:

  1. All energy on Earth comes from the sun, so all changes in heat are due to the sun.
  2. The climate has changed before; it’s a natural process.
  3. Earth has been hotter before, so it’s not going to be destroyed.
  4. The Earth is getting warmer, but humans aren’t causing it.
  5. The Earth is getting warmer, but it won’t cause dire effects.
  6. There actually isn’t a scientific consensus about climate change.
  7. The temperature data isn’t reliable.
  8. Actually, the Earth is getting cooler.

Some of these points are not very strong. Most, like carbon dioxide being essential to life or the fact that the Earth is currently in a cooling cycle, are based on sound facts at their roots but fall apart under scrutiny. The popular science site skepticalscience.com provides more discussion and detail in response to these claims, and I encourage those interested to visit that website, but these are the basic rebuttals:

  1. A change in energy coming into Earth is due to the sun, a change in energy retained is not.
  2. Climate change may be a natural process, but it is not an exclusively natural process.
  3. The Earth won’t be destroyed, but that isn’t the concern. The concern is that the livable area for eight billion people will be greatly reduced and countless species on the Earth will be destroyed, which will be catastrophic.
  4. Humans are increasing greenhouse gases, which increases global temperature, which causes climate change.
  5. The effects are not disastrous at the moment, but we are only just beginning to see the dire effects of climate change.
  6. There is a consensus.
  7. The data is reliable.
  8. It is true that on a geological scale, the Earth had been cooling. For the past 100 years, however, the Earth has been warming. If anything, the fact that the Earth is warming as quickly as it is in the midst of this geologic cooling trend bolsters the argument that we’re living through anthropogenic warming.

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Now what?

As I said in the beginning, this issue is not about telling you what can be done or what should be done or whose politics are right. Some people who believe climate change is a global threat have suggested very half-baked, self-defeating and ineffective solutions. Some people who have staked out political positions that are skeptical of the threat of climate change have simultaneously embraced solutions that may help control it for reasons other than fear of the climate crisis. The politics of all this, unlike the science, are not at all simple.

Others have seemingly lost their patience. David Archer, a professor of Geophysical Sciences at the University of Chicago who Ari studied under, is an expert in the carbon cycle and climate. He is also a contributor to RealClimate.org, “a commentary site on climate science by climate scientists.”

We asked him which projections appeared most accurate in his view. “So far we’re following the worst-case ‘business-as-usual’ scenario,” he said in an email. “So doomsday people have been right.”

We asked him what individuals can do, given that some of the major greenhouse gas emitters are corporations. “Not much,” he told us.

We asked him about efforts to reduce carbon footprints and the electric car revolution, which he described — in broad terms — as little more than “symbolic.”

We asked him, globally, what actions could be taken — actions that are achievable — to obtain the lower end of climate change projections. “I’m not optimistic,” he said simply.

I don’t share all this to be a doomsayer or depressing, only to tell the truth as I see it. Archer’s skepticism is that of one man — an expert and a professor, who has seemingly experienced the frustration of screaming into the void for many years. Lots of experts share Archer’s skepticism. Lots of other experts believe we still have time, that technological advances and political will can answer the call. I share that belief myself.

Two months into the coronavirus pandemic, I expressed optimism that we would witness the fastest production of safe and effective vaccines ever, largely because there was so much will and money behind it. I was right, happily. Not because I’m smart, but because I recognize that humans are an incredible, unstoppable, unbelievably clever and resourceful species when our backs are against the wall.

The problem with this issue is that far too many people don’t believe our backs are against the wall. My hope is that this newsletter can play some small part in convincing a few more people that they are.

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Isaac Saul
I'm a politics reporter who grew up in Bucks County, PA — one of the most politically divided counties in America. I'm trying to fix the way we consume political news.