The SuperFreakonomics Global-Warming Fact Quiz

By the time you finish this blog post, you will understand why we differ from our critics in our conclusions.

As we write in SuperFreakonomics, there are many misconceptions about the facts surrounding global warming. Take the following true/false quiz to test your knowledge of the science, economics, and technology of global warming.

Global-warming science questions:

1. The Earth has gotten substantially warmer over the past 100 years.


2. Even if we were to immediately and permanently stabilize our carbon emissions at the current levels, or even cut these emissions substantially, climate models predict that Earth will continue to get warmer for decades.


3. When Mt. Pinatubo erupted in 1991, it spewed millions of tons of sulfur dioxide into the stratosphere. Scientists believe that the haze generated by the eruption reflected some of the Sun’s light, causing the Earth’s temperature to temporarily drop as a consequence.


4. Because the half-life of sulfur dioxide in the stratosphere is relatively short (on the order of one year), the cooling effects of the Mt. Pinatubo eruption faded within a few years.


5. Dark surfaces absorb more sunlight than light surfaces. Thus, all else equal, light surfaces cause less global warming because more of the sunlight that strikes these surfaces is reflected back into space.


6. Clouds, which are white or gray, are lighter in color than the oceans, which are blue.


The correct answer to all six of these questions, we believe, is “TRUE.” You can see our chapter on global warming (pp. 165-209) and particularly the endnotes (pp. 247-256) for citations and elaboration. It is our impression that none of the six scientific statements above is at all controversial among climate scientists. I do not believe that any of our global-warming critics would quibble with any of these facts.

And just to be perfectly clear, despite all the bluster that has surrounded our chapter on global warming, these are the six scientific facts that are critical to our analysis of geo-engineering in that chapter, a point I will expand upon below. We document many other interesting facts in the chapter, but these are the only ones that are central to our argument.

It is simply not the case that criticisms of the geo-engineering solutions that we highlight in the chapter arise because we get the scientific facts wrong, unless the critics think that any of the six statements above are false.

So let’s move on to the economic issues surrounding global warming, and let’s see if that is where we differ from the critics in our assumptions.

Global warming economics questions:

1. If the Earth’s warming leads to global catastrophe, that would be a really bad outcome.


2. Even when there is enormous uncertainty about the likelihood of future cataclysms, it makes sense to invest now in finding ways to avoid such cataclysms.


3. Economists estimate that the costs of reducing carbon emissions are likely to be upwards of $1 trillion per year.


The correct answer to all three of these economic questions is “TRUE.” These are the three key economic facts that are critical to the arguments in our chapter. The first question doesn’t require any further explanation. The answer to the second question has been hammered home by Martin Weitzman‘s work in the area, which we cite in SuperFreakonomics, as well as a newer paper that Weitzman has written. The third fact is based on the analysis of Nicholas Stern. These cost estimates are obviously highly speculative, but the true cost of reducing carbon emissions is likely to be within two orders of magnitude of this number.

As far as I know, none of our critics would disagree with any of these three economic facts about global warming. Indeed, Paul Krugman‘s attack of our chapter largely focuses on the misconception that we do not agree with fact No. 2, when clearly we do. Somehow Krugman has come to the conclusion that we are in favor of inaction, missing the main point of the chapter, which is that we think immediate and aggressive action is warranted, in the form of investment in (or implementation of) geoengineering solutions. Perhaps Krugman does not consider those steps taking action.

So if there is no disagreement on either the six key scientific facts or the three key economic facts, where is the disagreement coming from?

Perhaps it is coming from a lack of agreement over technological facts.

Global warming technological questions:

1. There exists an engineering design that provides a means of delivering enough sulfur dioxide to the stratosphere on a continuous basis to effectively cool the Earth. The estimated cost of building and implementing this technology is a few hundred million dollars.


2. There exists an engineering design that provides a means of increasing oceanic cloud cover by seeding such clouds with salt-water that is sprayed into the air by a fleet of solar powered dinghies. The estimated cost of building and implementing this technology is a few hundred million dollars.


The answer to these questions is once again “TRUE.” As we describe in SuperFreakonomics, the Seattle-based company Intellectual Ventures has designs for both a “stratoshield” (No. 1) and the cloud-seeding project (No. 2).

I don’t see how the critics could argue with the answers to those two questions. They might argue that the technology won’t work as Intellectual Ventures hopes it will, but there is no arguing with the fact that Intellectual Ventures has the blueprints to try to build these contraptions, and could have them up and working within a year or two.

With all of this as preamble, let’s get to the fundamental question we try to answer in the chapter:

If we need to cool the Earth in a hurry, what is the best way to do it?

Our answer to that question follows directly from the three sets of facts I presented above. Reducing carbon emissions is not a great way of cooling the Earth in a hurry for two key reasons: (1) even if we cut carbon emissions today, the Earth will continue warming for decades; and (2) reducing carbon emissions is expensive, with a price tag of at least $1 trillion per year. (There is a third problem with reducing carbon emissions, which is that it requires worldwide behavioral change, which will be hard to achieve. But even beyond that, carbon mitigation is not a great solution to the question posed above. There might be other significant benefits tor reducing carbon emissions — addressing ocean acidification, for instance.)

A much better approach, we conclude, is geoengineering. The scientific evidence suggests that either the stratoshield or increased oceanic clouds would have a large and immediate impact on cooling the Earth, unlike carbon-emission reductions. The cost of these solutions is trivial compared to the cost of lowering carbon emissions — literally thousands of times cheaper! Perhaps best of all, if something goes wrong and we decide we don’t like the results of the stratoshield or the oceanic clouds, we can stop the programs immediately and any effects will quickly disappear. These two geo-engineering solutions are completely reversible. Given the huge costs of global cataclysm and how cheap the solutions are, it would be crazy not to move forward with geoengineering research in order to have these solutions ready to go in case we decide we need to cool the Earth.

Why then, are our our conclusions so radically different from those of our critics? The answer:

We are answering a different question than our critics.

Our question, at noted above, is what is the cheapest, fastest way to quickly cool the Earth. Like every question we tackle in Freakonomics and SuperFreakonomics, we approach the question like economists, using data and logic to conclude that the answer to that question is geo-engineering. Not coincidentally, almost every economist who has asked the same question has come to the same conclusion, including Martin Weitzman and the economists at the Copenhagen Consensus.

But that is not the question that Al Gore and the climate scientists are trying to answer. The sorts of questions they tend to ask are “What is the ‘right’ amount of carbon to emit?” or “Is it moral for this generation to put carbon into the air when future generations will pay the price?” or “What are the responsibilities of humankind to the planet?”

Unlike the question that we are asking — How can we most efficiently cool the Earth fast? — the types of questions that environmentalists are trying to answer mix together both scientific issues and moral/ethical issues. If you have any doubts about this, watch Al Gore’s movie, in which he says explicitly that reducing carbon emissions is not a political issue, but a moral issue.

That is why someone like Ken Caldeira can agree with the facts presented in our chapter, say that the chapter is written in good faith, but still disagree with the conclusion that geoengineering is the answer. It is because the question Ken Caldeira is trying to answer is not the question we are trying to answer. The same is true of our critics. But instead of just making this simple point — that we are asking different questions — the critics have either intentionally or unintentionally confused the issues by making all sorts of extraneous arguments.

I do not mean to imply that the question we answer in the book is the most important question. It may be that the questions that environmentalists are trying to ask are more important and more interesting, but that certainly does not mean that we don’t want to know the answer to our question, a question that the environmentalists don’t bother to ask very often because they are focused on their more philosophical questions.

So for all the blogosphere shouting against our chapter, I have to be honest and say that I just don’t get it. I can’t understand why any environmentalist who really cares about the Earth’s future could say with a straight face that geoengineering doesn’t deserve a seat at the table as the global-warming debate heats up.

Leave A Comment

Comments are moderated and generally will be posted if they are on-topic and not abusive.



View All Comments »
  1. Miguel says:

    I like the geo-engineering solution. But I was reading that one of the biggest problems with global warming is not actually the warming itself, but global climate change. So some places will get cooler, some hotter, and so on. The problem with this is that economies aren’t prepared for an abrupt change in climate. Some places just aren’t prepared for rain, some aren’t prepared for a lack of water, and so on.

    Couldn’t this cost even more?

    And would we be able to control geo-engineering so that climate keeps more or less consistent?

    What can you tell us about that?


    Thumb up 2 Thumb down 3
  2. Jason says:

    The question isn’t whether geoengineering deserves a seat at the table – everyone agrees it is worth researching. The question is whether it is worthwhile to expend resources to reduce carbon emissions immediately while this research is being conducted. Your critics seem to say, “Yes, it certainly is.” As far as I gather from this blog post, you are saying, “No, it isn’t.” To accuse your critics of failing to “approach the questions like economists” is extremely disingenuous. There is a substantive economic question here about whether geoengineering type solutions and reducing carbon emissions are substitutes or complements. You have failed to engage with your critics who argue that they are complements.

    Thumb up 6 Thumb down 4
  3. Mike says:

    Dr. Levitt,

    Unfortunately for you guys, the environmentalists could care less about logic and reason. Their only interest appears to be in sensationalizing their issue. It reminds me a bit of organized religion.

    “You will be damned if you don’t do what we want you to do”.

    I have made my peace with attempting to get through to people on this subject.

    I am a finance guy, so I’m pretty much evil anyway.

    Good luck.

    Thumb up 5 Thumb down 5
  4. Aaron says:

    As an engineer, I have some doubts as to truthfulness of the Geoengineering Technological questions you pose above. I have no doubt they have some fancy renderings, ( which they do, nicely contained in their white paper on the subject) But, renderings and white papers do not constitute a final design, and that “few hundred million dollars” is at best a +-50% estimate.

    So, does a concept exist? yes. Does a Design exist? No. It would probably take a few tens of millions of dollars to get to the final design, never mind the first prototype.

    Thumb up 4 Thumb down 1
  5. JW says:

    It would also be good if you added a Scientific Question 1.5: The vast majority of the Earth’s warming over the past 100 years is due to human release of greenhouse gases to the atmosphere. (Answer: true)

    Thumb up 4 Thumb down 4
  6. Cackalacka says:

    Hey, I got one for the authors:

    The argument apparently advanced by this chapter will be used by the fossil fuel lobby to hem and haw over potentially dire known consequences of their product:


    Thumb up 2 Thumb down 5
  7. Corey says:

    Without having read the chapter I hesitate to ask this, but are you asking the right question? You say that it might not be the most important question, and I think you may be right.

    As to why environmentalists wouldn’t want geoengineering to have a seat at the table, I can think of two reasons:

    1.) They’ve been advocating for decades that there are no shortcuts, that we have to behave more responsibly in order to save our planet. Geoengineering could suddenly prove this untrue — we could continue indulging ourselves at the planet’s expense, but we wouldn’t have to worry about at least global warming.

    2.) More importantly, there’s a really good chance it’s not the best solution — either morally or economically — to our environmental problems in the long-run. Geoengineering seems like it might be a good band-aid — we can halt global warming for a couple decades while we wait for the carbon in the atmosphere to dissipate — but seems unlikely to solve all of our problems in the long run. If we don’t slow down the rate of pollution b/c we can just make the earth cooler with more oceanic cloud cover, it most likely means that we won’t dramatically cut pollution and will face more problems with ocean acidification and such in the future. Not to mention that geoengineering will probably continue to get more expensive as we add carbon to the atmosphere while the cost of reducing carbon emissions will likely continue to get cheaper after we’ve done so and developed alternative technologies.

    In short: yes, you’re thinking like an economist when answer the the question. But maybe that’s the problem. Maybe that’s what people are objecting to.

    Thumb up 5 Thumb down 5
  8. Felix says:

    the ideas in the book are fascinaing from an innovation point of view, but the goal is to bring earth back to normal not to keep altering it.

    Thumb up 3 Thumb down 7