Wednesday, November 18, 2009

Answering a Middle School Student's Questions about Global Warming


When a middle schooler asks common questions about global warming, what do you say?

by E. Calvin Beisner, Ph.D.

National Spokesman, The Cornwall Alliance

Occasionally I receive emails from school children with questions about global warming. A particularly thoughtful one came recently from a student in Georgia, acting apparently on a teacher's assignment. Because the questions are so typical, I thought I'd share them my answers here.

1. Is global warming real and as large of a problem as some web sites tell the people?

This is an example of what logicians call the "fallacy of complex question." A "complex question" comes in the form of one that requires a "Yes" or "No" answer but that actually includes some parts that might be answered "Yes" and others that might be answered "No," or that asks only one thing, but answering either "Yes" or "No" implies something false. An example of the latter sort is the question, "Have you stopped beating your wife?" If you answer "No," you imply that you're still beating her; if you answer "Yes," you imply that you used to beat her. There is no way to give the grammatically required answer without condemning yourself. Similarly, the question above suggests that you want a "Yes" or "No" answer, but its first part ("Is global warming real" might receive a "Yes" answer without implying a "Yes" to the second part ("and as large of a problem as some web sites tell the people"). Further, the second part of the question almost necessitates a "No" answer, because some web sites make truly outrageous claims--e.g., that greenhouse warming might turn the Earth into a fiery ball. Absolutely no scientist I know of has suggested such a thing, but some laymen have. (Physicist Stephen Hawking came close when he suggested that runaway global warming could make Earth as hot as Venus, but Hawking was speaking off the cuff and hadn't really studied the particular physics of Earth's climate system. Probably it's not fair to take him seriously on the point.) To be sensibly answerable, your question needed to quantify what you meant by "as large of a problem as some web sites tell the people"--i.e., so large as to make life extinct on Earth, so large as to cause 20 degrees Centigrade increase in global average temperature, so large as to melt the Greenland or Antarctic ice cap, so large as to raise sea level by 1 foot, or 2 feet, or 3 feet, or 20 feet, or 60 feet, or so large as to cause massive deaths from heat stroke, etc. (The answer to all of those, by the way, is "No"--except to 1-foot to 2-foot sea level rise, and then the answer is "Maybe we'll see that much SLR (1 foot much more likely than 2), and maybe global warming will contribute partly to that (though it might be mostly just continued response of Earth's ice and oceans to warming that has already occurred).) Now, to the two parts of your question.

First: "Is global warming real?" Earth is always warming or cooling, in several cycles determined by cycles in solar energy and solar magnetic wind output; by cycles in ocean currents (the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation (AMO), the El Nino/La Nina Southern Oscillation (ENSO), and others); by volcanic activity; by cycles in Earth's orbit and tilt; by cycles in Earth's magnetic field; by cycles in the intensity of cosmic ray influx (which in turn are determined partly by cycles in solar magnetic wind intensity and partly by Earth's position relative to the various arms of the galaxy). The primary driver of changes in Earth's average surface temperature appears to be cloudiness, which in turn is determined mostly by ocean cycles, especially the PDO. From about A.D. 900 to about A.D. 1300 (the Medieval Warm Period), Earth's average temperature appears to have been considerably warmer than it is now. From about 1350 to about 1850 (the Little Ice Age), it was significantly cooler. From about 1850 to now it appears to have warmed by about 1 degree C (1.8 degree F), although there are some very serious problems with the accuracy and comparability of temperature data, and that figure really could range anywhere from 0 to 2 degrees C (0 to 3.6 F). But during that 160-year period, there have been ups and downs. Earth seems to have warmed generally from about 1850 to about 1900 or 1910, cooled from about 1910 to about 1920 or the mid-1920s, warmed from then to about the early 1940s (the 1930s probably being the warmest decade on record for both the Earth and the 48 contiguous United States), cooled somewhat from then to the mid-1970s, warmed from then to 1998 or perhaps 2001 (1998 being the warmest year since 1850 for Earth, but 1936 the warmest for the U.S.), and cooled since then. So: Is global warming real? Yes, of course it is--sometimes. And in between times, global cooling is real. That's no surprise to Earth scientists, or even to historians (who are aware, for instance, that during the Medieval Warm Period the Vikings colonized Greenland and Vinland (now called Newfoundland), naming the first as they did because its coastal regions were green and farmable, and the latter as they did because they found grape vines growing there, but that during the Little Ice Age Greenland's glaciers expanded so much as to destroy the colonies and the Vikings had to withdraw, and Vinland has not continued warm enough for grapes to grow, and that during the Little Ice Age the Thames River in London, which never freezes now, used to freeze over so solidly that Christmas parties were held on the ice, and similarly the Hudson River near what is now New York City).

Just so you can see for yourself how variable Earth's temperature can be even within a time as short as 1979 to the present, here's a graph representing satellite remote temperature sensing data for that period, from

Dr. Spencer (who's a friend of mine and runs NASA's Aqua Satellite remote sensing program) cautions that the running-average line, which many people ask for, isn't very significant. Have some fun looking carefully at that for a while and thinking about how large are the up-and-down cycles compared with whatever longer trend you might think you see. Now, think about 30 years compared with the last 300, 3,000, or 3 million, and ask yourself whether you think data for a 30-year period are enough on which to base a conclusion about a century-long or two- or three- or four-century long trend. Think how far wrong I could be if, out of a class of 30 students, I picked 3 and inferred from them average height, hair color, eye color, weight, or even gender of the class.

Now, be careful here: My saying "Yes" to "Is global warming real?" means only that: that sometimes Earth is warming, and sometimes it's cooling. It says nothing about the causes. But in most discussions today, the very phrase "global warming" is used as shorthand for "manmade global warming." To that, a different answer would be appropriate: "Maybe, but if so, only to a very slight degree; natural causes far outweigh human ones."

It occurs to me that I ought to give you a quick reason for why I assert that human influence on global climate is very small. It is this:

We know by basic physics that with no greenhouse effect, Earth's average surface temperature would be about 0 degree Fahrenheit. With the natural greenhouse effect, but without climate feedbacks (clouds, winds, evaporation, precipitation, wind, etc.), it would be about 140 degrees Fahrenheit. With the natural greenhouse effect plus climate feedbacks, it is about 59 degrees Fahrenheit. The climate feedbacks, in other words, eliminate about 58% of the greenhouse effect (59 is about 42% of 140). That means the climate feedbacks are net negative (reducing greenhouse warming), not net positive (which would increase greenhouse warming). We also know by basic physics that doubling the amount of CO2 in the atmosphere from pre-alleged industrial levels (going from 270 parts per million by volume [ppmv] to 540; so far CO2 concentration has only gone up to about 390 ppmv; by the way, I said "alleged" because there is good reason to think pre-industrial CO2 levels were significantly higher than 270 ppmv) would increase the greenhouse effect, before climate feedbacks, by about 2.16 degrees Fahrenheit. Since climate feedbacks would have the same effect on the added warming from the added CO2 that they have on the warming from the prior CO2 (and all the other greenhouse gases), we must subtract 58% from this to get the actual warming, after feedbacks, that would result from doubled CO2: 0.91 degree Fahrenheit. Nobody claims that this amount of warming would be dangerous. However, all the computer models on which some people (including those who lead the UN Intergovernmental Panel on Climate Change [IPCC]) depend for forecasts of possibly dangerous manmade warming assume that climate feedbacks are net positive (increasing greenhouse warming). For example, the IPCC claims a midrange estimate of warming from doubled CO2 of about 5.4 degrees Fahrenheit. To get that would require that feedbacks be very strongly net positive: adding 150%. That is the only way to generate the notion of a "positive feedback loop" that could cause "runaway global warming" and hence catastrophe. But that assumption is simply contrary to what we know the natural feedbacks do. A number of recent studies have called attention to this, and I believe this will eventually lead to the collapse of the fears of dangerous manmade global warming. See, for example:

Lindzen, Richard S., and Yong-Sang Choi, 2009. “On the determination of climate feedbacks from ERBE [Earth Radiation Budget Experiment] data,” Geophysical Research Letters, forthcoming (revised July 14, 2009), accessed online August 27, 2009, at

Lindzen, Richard S., Ming-Dah Chou, and Arthur H. Hou, 2001. “Does the Earth Have an Adaptive Infrared Iris?” Bulletin of the American Meteorological Society 82:3 (March), 417–32.

Spencer, Roy W., 2009. “Global Warming as a Natural Response to Cloud Changes Associated with the Pacific Decadal Oscillation,” accessed online August 27, 2009, at

Spencer, Roy W., and William D. Braswell, 2008. “Potential Biases in Feedback Diagnosis from Observational Data: A Simple Model Demonstration,” Journal of Climate 21 (November 1), accessed online August 27, 2009, at

Spencer, Roy W., W. D. Braswell, J. R. Christy, and J. Hnilo, 2007. “Cloud and radiation budget changes associated with tropical intraseasonal oscillations,” Geophysical Research Letters, 34, L15707, doi:10.1029/2007GL029698; accessed online August 27, 2009 at

Second: Is global warming "as large of a problem as some web sites tell the people?" Well, some web sites are telling people it's little or no problem--for those, the answer is "Yes." Some are telling people it's a moderate problem--for those, the answer is "Maybe" (although, as you'll see in answer to Question #2 below, what's a problem to some ecosystems, and people, may be a benefit to others). Some are telling people it's going to be a catastrophe--for those, the answer is "Almost certainly not."

2. Is global warming affecting the climate and the environment of arctic negatively?

This, too, is a complex question, because the climate and environment of the Arctic are not simple but complex. What is negative for some ecosystems is positive for others, and nobody knows what is best. We have no standard, no perfect ecosystem for any location, about which we can say, "This, and exactly this, is what conditions should be here, ever and always, and any deviation from it is negative." So, the proper answer to this question is "Probably yes, and probably no, and certainly not either yes or no exclusively." That is, to the extent that global warming is affecting the climate and the environment of the Arctic at all, the effects are necessarily positive for some and negative for other things living there (from people and polar bears and trees and moss to amoebas). But the crucial thing to keep in mind is that nobody knows what is best; there is no standard, perfect ecosystem for any location. Therefore nobody has any criterion (a standard of judgment) for saying what's going on there is "good" or "bad" and therefore should be cheered or mourned, tolerated or resisted.

3. What exactly is causing the global warming? Natural process or humans?

See my answer to Question 1.

4. What do you think about the idea of “Global Cooling”?

First, see the second paragraph of my answer to Question 1. Second, if by this you have particular reference to the claims in the news that Earth has been cooling for anywhere from the last five to the last 13 years, yes, something like that is probably true. We don't know how long the cooling will continue, or how great will be its magnitude

5. What percentage of ice in Arctic melted since Industrial Revolution?

Nobody knows, but we do know that the mass and extent of ice have grown and retreated cyclically over and over not only since the IR but throughout Earth's history. Arctic ice extent was almost certainly less in the 1930s than it has been recently, but I can only say "almost certainly" because our measuring methods have changed between then and now. There were no satellites then, and direct observation methods were poor and few, but we do know that shipping was able to navigate from Atlantic to Pacific (or vice versa) during several years in that decade in seasons when it hasn't been able to since then.

6. Have the temperatures been noticeably rising before the industrial revolution?

See the second paragraph of my answer to Question #1.

7. How much ice in polar bear habitat is being melted over one year?

I'm sure there are numbers available, but the really significant thing is that it's cyclical.

8. What would the consequences be if the polar bear habitat was completely destroyed? (Like as in all the ice melted in polar bear habitat?)

"Completely destroyed" and "all the ice melted in polar bear habitat" are not the same. "Completely destroyed" would mean there was no habitat left. Then, of course, there would be no polar bears or any other life left. "All the ice melted in polar bear habitat" wouldn't mean anything remotely like that. Now, keep in mind three things: (1) Polar bears are closely related to grizzly bears, and although they prefer to hunt from floating ice for seals and fish, they are perfectly capable of feeding themselves adequately from land on all kinds of animals or in rivers on fish. (2) Polar bears have been around for a very, very long time. They've certainly survived the Medieval Warm Period, which was warmer than the last thirty years.

And they survived the Holocene Climate Optimum (Notice that last word, by the way. What does it tell you about scientists' estimate of the effect of that climate on life?)

(3) The world's leading polar bear biologist, Mitch Taylor, reports that the populations of most polar bear colonies around the Arctic are either growing or stable, with only 2 out of 11 (or was it 2 out of 13?--I can't remember at the moment) declining. And the declines in those 2 have nothing to do with changes in temperature. They're caused by hunting.

9. How long will it take for the ice to melt in both poles if earth heats up at the rate it is heating up now?

Well, since Earth appears to be cooling now, the answer is "Forever." But if the question assumes something like "at the rate of about 0.7 degree C (1.26 degree F) per century" (maybe the approximate rate of the last 160 years), then the answer is "thousands and thousands of years."

10. About how much of the natural habitat is being destroyed because of global warming over one year?

None. Habitat is changing, but none is becoming non-habitat, i.e., uninhabitable for any life. And remember: There is no standard by which to judge that one habitat is naturally better than another. It all depends on the kind of life you're asking about. There appears to be no standard by which to prefer one kind of life over another, excluding human beings, which means there's no standard by which to prefer one habitat over another. The exception: if human beings are special (which as a Christian I believe, and which I think most people agree to--which is why killing a human being is a punishable crime, while killing most other living things isn't), then habitat suitable for human beings might be considered better than habitat not suitable for human beings. But human beings live in everything from frozen tundra to the Sahara Desert, from the highest mountains to the Netherlands (below sea level). We can adapt to any and every climate that might face us in the future. What we do know, however, from history is that warmer climates tend to be better for human health and longevity than colder climates, for a lot of different reasons, including higher agricultural yields (leading to more and better food) and less exposure to the danger of cold snaps (which on average kill about 10 times as many people per day of their duration than do heat waves).

11. Should governments take any actions in order to reduce greenhouse gas in the atmosphere?

No. Why? Because: (1) Human-induced greenhouse gas (GHG) emissions appear to have very, very little influence on global temperature, which means (a) they can't be the cause of much of either the harm or the benefit that comes from the consequent temperature changes, and (b) reducing them can't make a significant difference in future temperature. (2) The only means of reducing them is either (a) greatly diminished use of fossil fuels (coal, oil, and natural gas), which are far and away our cheapest and most abundant energy sources (except nuclear) and are far cleaner and safer than such gross biofuels as wood and dried dung (on which about 2 billion people rely for cooking and heating because they're too poor to afford anything else) or (b) extremely expensive carbon-capture-and-sequestration (which at this point is largely theoretical, not yet workable on large scale, as well as being extremely expensive). Either of those means of reducing CO2 (the main manmade greenhouse gas people are worried about) would drive the cost of energy much higher, and because we use energy in everything we produce, that would mean lowering standards of living. For most Americans, who by world standards are incredibly rich, that would mean only some adjustments at the margins of our luxury--psychologically painful, perhaps, but by no means devastating. For the roughly 2 billion people in the world who live in poverty, it would be devastating. It would slow, stop, or even reverse their economic development, i.e., their rise out of poverty, and so condemn them to added decades or generations of high rates of disease and premature death. That means prolonging the time when parents see 2 or 3 out of every 10 children born die before they reach age 5. It means prolonging the time when the average sub-Saharan African woman spends 6 to 8 hours every day just gathering enough fuel (sticks and dung) to cook and, in season, heat her hut, and she and her children get tuberculosis and other respiratory diseases from breathing the smoke inside their huts (killing 2 to 4 million per year) and her husband, too, gets sick and thus often can't work, further contributing to and prolonging their poverty. (3) The best economic studies find that the benefits (theoretically) achieved by the temperature reductions (theoretically) achieved by reducing GHG emissions would be far less than the costs incurred. The Copenhagen Consensus, for example (, finds that every dollar spent on carbon emission reductions brings only about 4 cents of social benefit--i.e., the other 96 cents is just lost.

12. Do you have anything to add? Do you have any opinions about this? If so, what are they?

Just one other thing: If you've been told there is some kind of vast scientific consensus that human action is the primary cause of recent global warming, don't believe it, and don't even consider it significant. Science doesn't work by consensus. It works by evidence and logic. Further, every attempt to provide evidence for the existence of such consensus has failed. The most thorough studies instead indicate that there is great debate among scientists (e.g., and Dishonest men like Al Gore claim there's a consensus. There is not.

I think what I've said above is probably sufficient to give you a sense of my opinions. Are they right? You need to study for yourself and see. I suggest you begin by reading I also invite you to subscribe to the Cornwall Alliance's weekly e-newsletter, which you can do by entering your email address in the subscription field at

I hope you'll share my response with other students and your teacher.

In Christ,
Dr. Beisner

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