Global Warming for Dummies

This work is based on my own research and represents my own beliefs after about 3,000 hours of research.

There actually is a Dummies book on global warming.

I don’t think people who believe in global warming are dummies. For example, I think these people are very smart:

Bill Gates, Warren Buffett, Tyler Cowen, Tom Steyer, Elon Musk, Mike Bloomberg, Jeff Skoll, Jeff Bezos, Leonardo diCaprio, Barack Obama, Hans Rosling (RIP), and all the Democratic candidates for president.

I don’t think they are dummies at all. But I do think they have been misled by a few people who are trying to create global warming hysteria. Since the 1980s, they have tried to influence the flow of research money, academic careers, government jobs, and the public narrative on environment and energy. There is a lot at stake. It’s difficult to find the truth amid the noise, misdirection, media manipulation, political grandstanding, fear, and panic. In this essay, I try to frame the problem and the proposed solution so everyone can see that this is a legitimate scientific debate.

I’m going to show graphs and make arguments. If you want the simple version, just watch the videos.


My name is David Siegel. My first book, which I wrote in 1991, was about global warming and how we had to be careful about carbon. In 2014, I revisited the science behind the projections. Initially, I trusted NASA, NOAA, and the UN — I thought they had good scientists doing important scientific research. Then a friend told me that “the science of global warming is settled.”

I know that if it’s settled, it isn’t science. So I spent 2015 looking into the science, the measurements, and the messaging, and I ended up changing my view. I wrote about that in a big essay called Climate Curious, which more than 300,000 people have read. My goal is to ask people to question their assumptions and question the authority and motivation of people promoting a climate crisis. Is it based on science or politics? In this essay, I’m going to break it down into the the two arguments I think are most important and then address what I think we should do.

Six Critical Questions

Framing is critical to understanding a difficult issue. The two big issues are data quality and model accuracy. In my view, these are the important questions:

  1. Is CO2 increasing?
  2. Is temperature increasing?
  3. Is there a causal relationship?
  4. What will happen in the future?
  5. What should we do about it?
  6. How would you feel if it turned out not to be a crisis?

I promise to do this as quickly as possible. Before I start, I will let Dick Lindzen sum up (highly recommended, but read my Prager U warning* at the bottom):

1. Is atmospheric CO2 increasing?

The answer is yes. It’s easy to measure the concentration of CO2 in the upper atmosphere, and for as long as we’ve been measuring, it’s been increasing on a seasonal basis (It goes up more as plants “exhale” during winter). Because natural processes (mostly organic decay) cause a lot of CO2 to go into the atmosphere each year, less than one percent is contributed by humans. But that’s more than there was before, so CO2 is accumulating in the upper atmosphere. There’s also more CO2 at ground level, which has increased the growth of plants worldwide. The effects on oceans is controversial; I have covered it elsewhere.

2. Is Temperature Increasing?

This is a much more difficult question than you might imagine. We have to learn something about the science and practice of measuring temperature. It breaks into three time periods: prehistoric, historic, and the satellite era.

My essay covers this in greater detail, so I will summarize:

We measure past temperature using proxies: ice cores that contain air trapped for millions of years, tree rings, peat bogs, sediment layers, and other methods. All of these are difficult and include many uncertainties. Burt Rutan has a slide deck showing:

As far as we can tell, the earth has been far hotter and far cooler in the past.

The earth has had far more CO2 in the atmosphere — possibly twenty times more than we have today. Historically, we are at a very low point in atmospheric CO2.

From ice cores, we know that the sun is highly influential. Here we see solar cycles called Milankovitch Cycles driving temperature, which later drives CO2 correspondingly. This is not disputed.

None of this shows that increasing CO2 drives an increase in temperature. In fact, as far as we can tell, the relationship is the other way around: increasing temperature results in more decay and more outgassing from the oceans, which results in more CO2 in the atmosphere hundreds of years later.

Here’s the famous “hockey stick” graph by Michael Mann that Al Gore featured so prominently in his movie:

Much has been written about this graph. It’s hard to take seriously. Mann generated this graph by cherry-picking tree-ring data.

Here is a more recent update on historical temperatures not using tree rings:

From Loehle, et al., 2008:

In this graph you can clearly see the Medieval warm period, which was worldwide, and the “little ice age,” which forced people to leave Greenland and Iceland. I’ll let Patrick Moore summarize*:

In the late 1800s, the US government set up weather stations around the country and started keeping records by hand. Almost all of them were located in a field outside of towns and cities, and many of them were rural. This station, in Nyssa, Oregon, is typical.

Fifty years ago, this station was probably out in a field by itself. Today, it could be influenced by cars, lawn mowers, city heat, and HVAC equipment.

Cities can have a huge effect on temperature measurement: there is more black surface, less wind, more exhaust, and more heat coming from air-conditioning and other equipment. The closer a weather station is to these kinds of developments, the hotter the thermometers will read. This is called the heat-island effect — you can see how much hotter cities are using satellite data from space:

Nor can you move the stations. If ten percent of weather stations moved each year, we would have no way to track temperature over time. You can remove weather stations from the system, but you can’t add new ones, because that changes the historical data. Yet, many weather stations have been compromised, which compromises our picture of past temperatures. Here’s one in Tucson, Arizona that used to be out in the middle of a field:

Do you think that station reads hotter now than it did fifty years ago? A survey of urban vs isolated stations shows clear warming in the urban stations but no warming in the isolated ones.

To have a coherent temperature record over decades, you must take station and data quality into account. How you do that determines the temperature record you show to the public. There are three strategies for “adjusting” your raw data:

Strategy 1: Eliminate compromised data. This is the rigorous approach taken by, a volunteer group headed by Anthony Watts who want to preserve the integrity of the temperature record in the United States. They devised a system for ranking weather stations from 1) unchanged to 5) completely compromised. They have rated over 1,000 stations using the same calibrated criteria. In general, categories 1 and 2 are still reliable, and from 3 up there is significant interference over time. Here is what they found:

Note that only 13 percent of those stations are at level 1 or 2, the rest have been materially compromised. Here is a map of the stations they surveyed (yellow, orange, and red indicate compromised locations):

It’s instructive to read the Surface Stations report, because it is very detailed and shows how many weather stations are reporting artificially high temperatures as their environment heats up. In fact, in 2013, the government closed some 600 stations because their data was compromised.

What it boils down to, Watts says, is that some of the world’s top climate scientists have been crunching numbers that were altered by their immediate surroundings, rounded by volunteers, guessed at by the NCDC if there was insufficient data, then further adjusted to correct for “biases,” including the uneven times of day when measurements were taken — all ending up with a number that is 0.6 degrees warmer than the raw data, which Watts believes is itself suspect. — Fox News report

Strategy 2: Blend compromised data in with other data. Here is the NASA GISS graph from1999, which includes most of the compromised weather stations:

Keep in mind that US data is far higher quality than the rest of the world. The data on the left is far better than that on the right, and it probably still has a rising heat bias due to the many compromised stations. The UN chose the image on the right to represent world temperature in their 2001 report. Homogenization is the practice of using bad data to distort good data.

Strategy 3: Adjust the data to suit your agenda. By 2019, government agencies needed more ammunition, so they simply made up the numbers, cooling the past and heating the recent decades:

There is much more on this at Tony Heller’s web site. If you have gotten this far, you should watch at least the first half of this talk:

Let’s look at the Reykjavik station, which has kept good records for more than a century:

Image courtesy Tony Heller,

Here is NASA’s version of that same station’s data:

Image courtesy Tony Heller,

I checked with Fausti, the guy in charge of the Reykjavik data, and he said NASA’s graph was not his data, it was made up.

Tony Heller explains that Greenland is not losing ice each year (this is an important video, please watch it):

Here’s a quick look at extreme temperatures in the United States, measured in heat waves (consecutive days well above normal):

Look how many super hot days we had in the US before 1950! When you hear “hottest year on record,” you might want to ask: “Since when?” The period from 1870 to 1940 was devastatingly hot, both in Europe and in the US. In 1911, a two-month heat wave in Paris killed more than 40,000 people. All of this long before CO2 started to increase.

What about extreme weather? I’ll let Bjorn Lomborg take you through the data (important and short*):

In fact, I highly recommend reading Lomborg’s piece, How Climate Policies Hurt the Poor.

Satellite data is far more accurate than thermometers on the ground. We’ve had good satellite measurements since the early 1970s, and here’s what two of the world’s foremost satellite measurement experts published this year:

Note that 1998 was an extreme el-Nino year. But look at the scale: Since 1980, we’ve seen roughly .5 degree C warming, mostly driven by el-Nino years, even as CO2 has been increasing and increasing. That’s .5 degrees in 40 years. If it happens twice again in a row, we’ll see about 1 degree C by the end of the century, which would be pretty much in line with the previous two centuries. Is man really driving temperature?

Understanding climate change has everything to do with understanding past temperatures. My hunch is that 90 percent of the “warming” we have seen in the past 70 years comes from compromised weather stations and el Ninos, and the other 10 percent is the continued natural rise we’ve been seeing for 200 years now.

There could be a small amount attributable to increased CO2, but it sure is hard to see in the data. There have been much hotter times in the past, without the CO2 added. There has been much more CO2, without the heat.

3. Is there a Causal Relationship?

The IPCC has turned alarmism into a mini-industry spending trillions of dollars each year to prevent “carbon dioxide pollution,” yet scientists do not agree that burning fossil fuels will cause disruptive changes to the climate. Close to 100 percent of climate scientists agree that added CO2 could contribute to global temperatures in the future, but many of them do not agree that this contribution is significant.

It’s a difficult thing to prove. In the past, scientists have been wrong about so many predictions that it’s hard to believe we know with much certainty what the temperature will be 80 years from now. Tony Heller shows that we have had bad or extreme weather forever, and CO2 really can’t be responsible:

4. What will happen in the future?

Predicting the future is difficult. People use models to try to show what will happen. This is important — if there really is a danger of extreme temperatures in the far future, we should probably try to do something about it today. But, if the models are manipulated to create dramatic headlines that drive fear, uncertainty, and doubt in the public, then we have to wonder how accurate or useful the models are.

“Scientists” have been modeling climate and making predictions since the 1980s. How well have they done so far? I encourage you to read John Christy’s U.S. House Committee on Science, Space & Technology on 2 February 2016. It starts like this:

He then shows the discrepancy between almost all models and the actual measured temperature:

I believe the blue line, generated by the UAH satellite team of John Christy and Roy Spencer, is probably the most accurate temperature data we have (it’s a simplified version of the blue line from the previous section). It shows the continued slow rise of temperature we’ve seen for the past 200 years. That picture speaks volumes about how we model future temperature. They don’t have it working yet. Here is John Christy to explain (important):

The biggest problem with most climate models is that they are politically motivated to show dramatic warming in the future. Technically, they are full of uncertainties.

An example is clouds. As the incoming radiation from the sun increases, increased temperatures drive more water vapor into the air. Water vapor is even better at trapping heat than CO2 is. So if the water vapor stays transparent, you get warming. However, if the water vapor turns into clouds, they reflect incoming energy from the sun and cool the surface of the earth. It’s easy to design a model with any degree of cloud formation, and that’s what they do. They assume there won’t be much new cloud formation.

The other problem is ocean heat. Oceans are like huge batteries — they can store and release heat in complex cycles, which we know causes the el Nino and la Nina weather patterns. These cycles produce the “high points” on the temperature graphs you see. We have almost no idea how CO2 affects these cycles, but we do know they have been creating hot years for millennia.

If you’re interested in the details of climate models, here are three key resources:

  1. Judith Curry’s report on climate models for non-scientists.
  2. Bob Tisdale’s blog and books.
  3. An important paper from 2017 methodically showing that between 2000 and 2015 models kept improving and dramatically lowering their estimates of climate sensitivity to increased CO2. Figure 7 is the smoking gun.

Here is Will Happer to explain in simple terms why computer models of future temperature are not credible:*

To summarize, here is Alex Epstein on future predictions (highly recommended):

Finally, it helps to understand that the major scientific publications are very biased toward publishing papers that predict catastrophic warming. Science itself has been hijacked for a political cause that has no basis in fact or reason.

5. What Should We Do About it?

Worldwide, humans are now spending around $1 trillion on climate research, alarmism, and decarbonization. In my view, we should focus on the environment, not on decarbonization.

Matt Ridley, a member of the British House of Lords, says that even if you agree with the IPCC, economic growth saves us from catastrophic warming (important):

We should also take the press to task for strongly misleading the public. There is no question that leading newspapers and science magazines are deliberately fanning the flames of climate alarmism:

Is there an “overwhelming consensus?” The press would like us to think so, yet over 9,000 Americans with PhDs (including many with degrees in earth or environmental science, math, statistics, physics, and aerospace) signed a petition stating:

There is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gases is causing or will, in the foreseeable future, cause catastrophic heating of the earth’s atmosphere and disruption of the earth’s climate. Moreover, there is substantial scientific evidence that increases in atmospheric carbon dioxide produce many beneficial effects upon the natural plant and animal environments of the earth.

In addition, 49 former NASA employees signed a letter asking NASA to stay out of the climate debate.

If you wanted to hijack the national conversation on science funding and research, all you need is a scary story of impending doom and images of death and destruction and the press will do most of your work for you. As we have seen, they are happy to do it whether it’s cooling or warming — they don’t seem to care, as long as it’s apocalyptic.

How well have Al Gore’s predictions panned out? Not one of his predictions has come true, not even close. (You may remember he received a Nobel Prize for sounding the alarm.) I go into more detail in

There’s only one problem with using polar bears as your media mascot for a worldwide climate crisis: they refuse to die of starvation. Mitch Taylor, who has studied polar bears for over 30 years, says populations are increasing and very resilient. Susan Crockford presents the data in her book, showing that polar bear populations are doing well despite the fact that Arctic sea ice grows and shrinks by an area almost the size of the continental United States every six months, and the bears are used to it.

Did you know that each year at least 600 polar bears are shot, killed, and eaten by hunters? That’s about 6,000 bears every ten years. Hold on. That’s 18,000 bears every thirty years! Out of a total population of about 25,000. Are people destroying the polar bear population by flying around the world and melting the ice, or are they getting out of their HumVees and shooting too many bears? Check my math, please:

How is this a CO2-driven tragedy of epic proportions?

Finally, I will mention the film industry. In the old days, Hitler or the Russians were the arch nemesis. Now it’s mankind fouling his own nest. I can’t count the number of big-budget films where the premise is that Earth is toast and we have to find a way to survive by going to other planets, underground, out into the desert with lots of marauding scavengers, no water, too much water, no air, no shelter, climate-driven disease, climate-driven war, anarchy, etc. Even George Clooney’s Tomorrowland was based on the story of escaping a scorching earth. Interstellar was about “time running out” on earth and the search for a new home. Godzilla was about monsters curing the earth of the human environmental-destruction virus. And on and on. Climate apocalypse has replaced the Emperor in many of today’s films.

If you’re a Hollywood film producer, don’t read Jesse Ausubel’s extensive inventory of how well the environment is actually doing — you’ll be out of a bad guy.

6. How Would you Feel if it Turned out not to be a Crisis?

It’s not easy to change your mind, but here is a test, to see if you are even willing: If somehow a large number of credible scientists were to actually admit that close to 100 percent of observed and future climate change is not related to CO2 and that whatever happens we will have plenty of time to adapt to naturally very slowly rising sea levels and temperature, how would you react? How would you feel?

Would you be happy or sad? Would you be relieved, or would you be frustrated and angry?

I think a lot of climate activists would be angry, they would prefer mass starvation and death to a false alarm. Why? Because they are so engaged, so passionate, so committed, and their funding and identity come from raising the alarm. If you would be disappointed, that’s a sign that you are not neutral, that you have a strong belief regardless of what the science shows, and that you strongly identify with others who are also fighting to save the planet from future climate destruction.

If you have read this far and you still feel I’m dead wrong, you are probably so set in your thinking on the issue that no amount of data will change your mind. I think this is true of every one of the Democratic candidates for president now — they have to run on a platform with climate at the center, because that’s where the votes are. It’s an inadequate equilibrium. It’s about political control, not about science.

Some day, we will have much more clean energy in the form of nuclear energy. Renewables will play almost no role in future energy, because they require dispatchable power as back-up. People who care about the environment should care about outdoor and indoor smoke (which kills more than 4 million people per year), smoking cigarettes (7 million), polluted cities (9 million), deforestation as a result of clearing for pastures, chemicals in our water, reduced aquifers, slow economic growth, and other important issues. I don’t think anything we do about carbon dioxide will have any meaningful impact on temperatures. We can stop worrying about “climate refugees” and start trying to help those burning wood for heat in their homes.

It comes down to understanding the quality of the data and the models.

If it turns out that the skeptics are wrong and a few people at NOAA who are responsible for publishing temperature data are right, if the hockey-stick graphs represent reality, then I think the world should know about it, conservatives should understand it, and we should unite immediately to decarbonize and save the earth.

If, on the other hand, most of the data that “scientists” use to write papers and predict future catastrophe have simply been crafted to suit political ends, then I think the world should know that, liberals should come to grips with reality, and we should unite immediately to focus on critical economic and environmental issues of the 21st century.

I would love to see a serious conference that goes into the details on the assumptions and the data and the uncertainties of the models. I suggest that to attend this conference, you should have to write down what you would have to believe differently to change your mind. Afterward, each participant should explain whether those criteria were met. I think if Bill Gates, Jeff Bezos, Elon Musk, and others really understood the accuracy of our data and the political nature of the assumptions that go into the models, we would have a more productive conversation about the environment and human welfare.

Because the major publications refuse to accept any papers that question the evidence, I have published a page on recent scientific work on climate change.

*Prager U is a religious conservative think tank with an agenda to promote religious conservative values. I don’t agree with most of what they stand for, and I think many of their videos are religious propaganda. However, they have made a series of high-quality, short videos on climate change that I feel are worth watching. Without them, you would have to listen to those same people testifying before various government panels. I recommend these few Prager videos but not the rest.

David Siegel is a serial entrepreneur, researcher, and writer based in Washington, DC. His previous essays on climate include Climate Curious and In Memory of Hans Rosling. He is also the author of His new project is about rationality and digital money. Please sign up for his newsletter at

Provocateur, professional heretic, slayer of myths, speaker of truthiness to powerfulness, and defender of the Oxford comma.

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store