The Goldilocks Effect and Global Warming:
A Guide to Environmental Change
Remember this passage from the story of Goldilocks?At the table in the kitchen, there were three bowls of porridge. Goldilocks was hungry. She tasted the porridge from the first bowl.Astronomers used to refer to the earth's present comfortable distance from the sun as "the Goldilocks effect." (Bryson, p. 17) The earth is just the right size and just the right distance from the sun, which is also just the right size, to be a cozy home for the human race. If we were a bit closer to the sun, it would be too hot to live; if we were a bit further away from the sun, we would all be frozen solid. But just like Baby Bear's porridge, the climate of the earth is just right! At, least that was what I was taught when I was in school.
"This porridge is too hot!" she exclaimed.
So, she tasted the porridge from the second bowl.
"This porridge is too cold," she said.
So, she tasted the last bowl of porridge.
"Ahhh, this porridge is just right," she said happily and she ate it all up.
Lately, however, all sorts of environmentalists and conservationists are predicting global disasters such as massive flooding of coastal cities, mass extinctions of various species such as the polar bear and maybe even the extinction of the human species. For the past forty years or fifty years, a constantly increasing number of scientists and non-scientists have been devoting much of their time to predicting how we are headed for a global catastrophe. Such grim predictions are also the main business of some politicians and social reformers like Al Gore. (Wikipedia, "Truth")
The common theme to most of these gloomy predictions is that human activity is changing our climate. Basically the predictions claim that the human race is destroying the Goldilocks effect.
You know what I mean. Global warming, and all that jazz!
Ever since Rachel Carson's 1962 success, Silent Spring, predicted that the chemical industry would soon destroy our environment with DDT (Lear), many environmentalists, conservationists, and scientists have used various nightmarish predictions of future environmental disasters to pressure lawmakers into creating legislation such as "clean air" and "clean water" acts and agencies such as the Environmental Protection Agency. So it is not surprising that we now are hearing calls for legislation to protect us from an impending global warming disaster. In a word, politics has become a part of scientific debate about climatology.
Unfortunately, climatology is a difficult and extremely technical science; so what I am doing here is giving a non-technical overview of basic climatology in an attempt to help you deal with what are really technical, not political, questions. Face it, Dear Reader, being a good Conservative Republican or a good Liberal Democrat, does not really prepare you to form opinions about scientific questions. (See Appendix A: Politics, Religion, and Science)
So, here's the main question: what scientific and mathematical principles do voters and law-makers really need to understand in order to decide whether the current discussions of global warming make any sense or not?
Another way of putting that question is: what factors are known to influence the climate of our planet?
Let's start with the Milankovitch cycles.
I. Have You Ever Heard of Milankovitch Cycles?
Obviously the most important factor in the earth's temperature is how much sunlight reaches the earth's surface. The closer the earth (or some part of the earth) is to the sun, the more sunlight reaches our planet. But there are three important variables which affect the distance between the sun and the earth. According to Matt Beedle of the University of Montana,variations in the Earth's eccentricity, axial tilt, and precession comprise the three dominant cycles, collectively known as the Milankovitch Cycles for Milutin Milankovitch, the Serbian astronomer who is generally credited with calculating their magnitude. Taken in unison, variations in these three cycles creates alterations in the seasonality of solar radiation reaching the Earth's surface. These times of increased or decreased solar radiation directly influence the Earth's climate system, thus impacting the advance and retreat of Earth's glaciers. (Beedle)Let's translate that into plain English.
The eccentricity (or shape) of the earth's orbit around the sun varies over a period of about 100,000 years from being nearly a perfect circle to being quite elliptical. This means that when the orbit is more elliptical the seasons of the year vary more in length than when the orbit is circular. Obviously in a period of longer summers and shorter winters there would be more melting of polar glaciers than there would be in a period of longer winters and shorter summers. Equally obviously shorter summers and longer winters would mean less melting of polar ice.
The axial tilt of the earth simply means that the earth's axis is tilted so that for about half the year the northern hemisphere is closer to the sun the southern hemisphere. Over a period of tens of thousands of years, however, that angle of tilt varies a few degrees. The further the axis is tilted away from the sun, the less solar energy arrives during winter; the more upright or vertical the axis is, the more solar energy arrives during the winter. In other words, the changing angle of the axis tends to make the average temperatures of all the seasons a bit cooler or a bit warmer. Obviously warmer summers and warmer winters would mean more melting of polar ice. Equally obviously cooler summers and cooler winters would mean less melting of polar ice.
The precession (or wobbling) of the earth's axis means that the earth turns on its axis a bit like a poorly aligned tire. Again, over a period of tens of thousands of years the wobbling slightly increases or decreases the angle of the axis and thus heightens or lessens the effect on the seasons caused by axial tilt.
Because these three factors known as Milankovitch cycles vary at different rates, sometimes all three will favor cooling; at other times all three will favor warming; usually, however, two of the factors point one way and one of the factors points in the other direction. Simply put, the Milakovitch cycles sometimes favor warming and sometimes favor cooling and these cycles tend to influence global climate for periods of thousands of years.
Nearly all authorities believe that the Milankovitch cycles are a very important factor in accounting for the advance and retreat of glaciers. What the authorities are unable to agree on so far is just how much weight to give to these cycles when comparing them to other factors that affect the climate of our planet.(Beedle; Kaplan; Rosenberg; U.S. Geological Survey)
"Holy Goldilocks, Batman! There are other factors?" Yes, there are quite a few more.
Let's look at another important influence on climate called albedo.
II. Have You Ever Heard About Albedo?
Because of the Milankovitch cycles (and other factors we will look at bit further down) always huge but significantly varying amounts of solar energy strike the earth's surface. So what happens then?
Some of the energy from the incoming sunlight is absorbed by the earth's surface and is then re-radiated into the lower atmosphere as heat, but some is reflected back into space as sunlight without significantly heating the lower atmosphere. Obviously the more heat that the surface absorbs, the more the climate will tend to be a bit warmer; equally obviously the more solar energy that is reflected back into space, the more the climate will tend to be a bit cooler.
By the way, you already know that lunar astronauts back during NASA's Apollo missions used to take photographs of the earth. From the moon, the earth was a spectacular sight indeed. Well, the astronauts wouldn't even have been able to see the earth if some of the sunlight was not bouncing off the earth. In technical terms, the albedo of earth is high enough that about a third of the incoming sunlight is reflected back into space, and that's why the astronauts got those spectacular photographs.(NASA, "Earthshine"; Answers)
Before moving on, just a bit more about lunar photography and albedo. A picture of the full moon taken from earth can be spectacular even though the moon's albedo is only 0.07, but a picture of the earth taken from the moon is truly impressive because the earth's albedo is 0.28. (Columbia) In other words, the earth appears to be four times brighter than the moon!
So, simply stated, albedo measures the percentage of solar energy that is reflected back into space. Actually what we are talking about is this. Some parts of the earth are "shinier" than others. Snow and ice reflect solar energy back into space very well. So does dry, light-colored desert sand. So does the top surface of cloud cover. The more "shiny" surfaces there are on earth, the more sunlight is reflected back into space without really warming up the atmosphere. (Wikipedia, "Albedo"; Answers)
Other parts of the earth are not very shiny or reflective at all. Water, vegetation, and most dry land surfaces absorb more energy than they reflect. Dark roofs and asphalt roads and parking lots are able to absorb large percentages of the solar energy that strikes them. All of these "non-shiny" surfaces absorb the solar energy and then radiate heat into the lower atmosphere.
In other words, the albedo of the earth varies from place to place. The average for the whole earth is about 0.28 to 0.30 (i.e., the earth reflects away from 28% to 30 % of the sunlight that falls on it), but where there is a lot of "shiny" ice and snow it is much higher; and over vegetation-rich tropical areas it is much lower.
So here's what happens:
If the Milankovitch cycles and/or some other causes start to melt some of the ice and snow at the poles, the albedo in the polar regions will begin to rise. That will cause more solar energy to be absorbed in those regions, and that will cause the snow and ice to melt even faster, and that will cause the albedo to rise even faster.
If something causes the winters to be longer and thereby allow more snow and ice to accumulate, the albedo in that area will start to drop, and that will cause less solar energy to be absorbed, and that will cause the temperatures to be even cooler, and that will cause the albedo to drop even faster.
But, remember axial tilt and precession. Those factors also affect the amount of solar energy that arrives in the polar regions. And remember orbital eccentricity. That affects the length of the seasons. (Beedle) If a drop in albedo was in phase with a period when the Milankovitch cycles were favoring additional warming, then the additional melting and ice and snow would further lower the earth's albedo, which would enhance the warming effect even further. In other words, the tendency toward global warming would intensify. On the other hand, if a rise in albedo was in phase with a period when the Milankovitch cycles favored additional cooling, then the increasing amounts of snow and ice would further raise the earth's albedo, which would enhance the cooling effect even further. In other words, the tendency toward global cooling would intensify.
Hey, Goldilocks! It seems that sometimes all the porridge is getting hotter and that other times all the porridge is getting colder. It may well be that you were just lucky to find any suitable porridge at all on the day you visited the Bears' cottage.
III. Have You Ever Heard About the Maunder Minimum?
So far we have the three Milankovitch cycles allowing varying amounts of solar energy to fall on the earth's surface where varying proportions of that energy, depending on the varying albedo of earth's surface, are absorbed by the surface or reflected back into space. The absorbed energy warms the surface, but the reflected energy bounces off into space without affecting the earth's temperature.
These four factors cause the temperature of the earth to vary at different rates and intensities. Sometimes the net effect of these factors forces the planet toward a warmer average temperature; sometimes the net effect forces the planet toward lower temperatures.
But there are still other factors which tend to disturb the Goldilocks effect to a greater or lesser extent. One of those additional factors is the sunspot cycle. So listen now to the story of sunspots and the Maunder Minimum.
Sometimes called the solar cycle, the sunspot cycle refers to the appearance and disappearance of dark spots near the sun's equator. Sometimes there are as many as 200 spots simultaneously circulating around the sun's surface; sometimes there are only one or two spots. On the average, however,a solar minimum (or maximum) occurs every eleven years. Astronomers have been keeping a pretty accurate record of sunspot numbers ever since the invention of the telescope, so we have accurate sunspot counts back to the early 1600's. (White)
And this is where the Maunder Minimum comes into our understanding of climatology. From about 1645 to about 1715, a period of about 70 years, sunspots were at an all-time minimum. During that period only 40 or 50 sunspots were counted whereas normally astronomers will record nearly 100,000 sunspots during a period of 70 years. (Colorado Research)
Climatologists have long suspected that increased sunspot activity means warming on earth, but recent studies at Miami University of Ohio strongly confirm that suspicion. As a result, nearly all scientists take seriously the idea that the Maunder Minimum led to the so-called Little Ice Age during that same period. As Professor Greene puts it, "we have shown that a larger amount of sunspots will correlate to a higher average [global] temperature." (Greene)
By the way, the Colorado Research article cited above, describes some of the effects of the Little Ice Age: the expansion of glaciers far enough down the slopes of the Alps to actually destroy some Alpine villages, the Thames River in London freezing over solid for six months of the year, the disruption of agriculture all over the Northern Hemisphere, the harsh winters in North America that settlers faced during the 1600's. The same article also includes late 17th Century paintings depicting the unusually frosty conditions of those times. When the sunspot cycle returned to its more familiar 11-year cycle, the northern hemisphere began to warm back up.
"Oh, come on, Professor," cried Goldilocks when she reached this point in my essay. "That's five factors which affect the climate. How is anyone going to be able to predict future climate accurately with all those factors reinforcing warming sometimes and cooling at other times and sometimes cancelling each other out to a greater or lesser extent?"
"Dear child," I replied, "you ain't seen nothin' yet. Wait 'til we start looking at greenhouse gases and aerosols."
IV. Did You Know Water Vapor is the Main Greenhouse Gas?
A greenhouse gas is neither good nor bad in and of itself, but above average amounts of greenhouse gas in the lower atmosphere force the temperature of the atmosphere upward; below average amounts of greenhouse gas force the temperature downward. When, for example, the Philippines volcano Mount Pinatubo erupted in 1991, climatologists discovered that the eruption dramatically lowered the amount of water vapor in surrounding areas, and that forced temperatures to cool down a bit until evaporation of ocean water restored water vapor amounts to familiar levels. (Soden)
That all happened because water vapor is a greenhouse gas.
"More factors?" asked Goldilocks.
"Yes," I replied, "and here's how it works."
The albedo of the earth is so high that too much sunlight is reflected into space. If we didn't have some greenhouse gases to trap some heat for us, our planet would be far too cold.
Appendix A: Politics, Religion, and Science
Republicans who dislike Al Gore attack his views on global warming more because he is a political opponent than because he is factually incorrect in his statements about the science of climatology. Democrats who dislike President Bush attack his position on global warming more because he is a political opponent than because he is scientifically unsophisiticated. It may be that the science of climatology is so hard to understand that various political and religious interest groups shape their view of global warming on political and religious beliefs rather than on the best scientific knowledge. Consider, for example, the following:If you thought Hurricane Katrina was a once-in-a-lifetime fluke, think again. Concerned environmentalists say that unless the United States gets real about the threat of global warming, African Americans and other people of color can expect a repeat of disasters like Katrina. (Britt)It seems that Mr. Britt, a more or less influential writer for the Black Entertainment Television Network, thinks that Mother Nature is just another racist, that the government of the U.S. is, as usual, ignoring the plight of minorities, and that it is a proven fact that Hurricane Katrina was due to global warming.
Or consider this example of what Baptists are saying about global warming:Ethics Daily [a journal devoted to discussing current ethical issues] has published an essay about the efforts of Baptist Press and fundamentalist leaders of the Southern Baptist Convention to deride Al Gore and discount the reality of global warming. (Prescott)Surely, Dear Reader, you can see that both Ethics Daily and the Southern Baptist Convention are arguing about global warming from a doctrinal rather than a scientific perspective. The Baptists, it seems, are denying the reality of global warming for theological reasons.
Look then at what the U.S. Conference of Catholic Bishops agreed upon in 2001 as a policy statement of the Roman Catholic Curch in North America:At its core, global climate change is not about economic theory or political platforms, nor about partisan advantage or interest group pressures. It is about the future of God's creation and the one human family. It is about protecting both "the human environment" and the natural environment. It is about our human stewardship of God's creation and our responsibility to those who come after us. With these reflections, we seek to offer a word of caution and a plea for genuine dialogue as the United States and other nations face decisions about how best to respond to the challenges of global climate change. (U.S. Conference of Catholic Bishops)Although the Catholic Church seems to accept the reality of global warming, their position is essentially presented as a moral issue rather than a scientific issue.
More examples would not make this point any clearer. Non-scientists usually base their arguments on non-scientific bodies of knowledge or extremely unscientific theological premises.
Appendix B: Computer Models
Everyone who is paying attention knows that computer games keep getting more realistic all the time. For example, one of my sons regularly plays a computer version of soccer that has recently added to the problems of being a skillful video game player the problems of being a coach and/or the problems of being a team owner. In addition to developing hand-eye coordination skills required to operate the game, he has to deal with such coaching and ownership problems as substituting fresh players for tired players, purchasing new players without over-running the budget for the team, keeping the good will of the fans, and other problems that real-world coaches and owners have to face. By the way, the first time my son played the new version of the soccer game, he finished first in the league for the regular season of about twenty games, but at the cost of over-spending his budget and being left with only eleven exhausted players on his roster. When he went to the league championship tournament, he lost in the first round even though he was a number one seed in the tournament. The result, according to the computer, was that he was fired as coach by the team owners and was forced to choose between retirement or accepting employment with a second-rate team in a less prestigious league.
Hey! That sounds a like lot real life to me.
Actually, however, the computerized soccer game is an example of what scientists call computer modelling. A combination of visual animations, recordings of crowd noise and the comments of sports announcers, financial transaction records, probability equations, league statistics, the rules of soccer, and so forth are put into one program which attempts to mimic competition in a real-world soccer league.
Each new version of the game has been tweaked to make the game seem more realistic. The computer programmer is constantly striving to make the game more realistic, so the program keeps being altered by the programmers to make the game player "feel" more like he is in the real world.
And that's what climatologists do under the heading of "scientific climatological research." They play computer games.
The U.K.'s scientific heart at the Hadley Centre, for example, has a whole bunch of different computer models of how earth's climate operates. They have AGCM's (Atmosphere General Circulation Models). They have OGCM's (Ocean General Circulation Models). They have CCM's (Carbon Cycle Models). They have super-sophisticated combination models like the AOGCM's (Atmosphere-Ocean General Circulation Models). They even have RCM's (Regional Climate Models).
Answers Corporation. "Albedo: Definition and Much More," Answers.Com. http://www.answers.com/topic/albedo. Website accessed on March 31, 2007.
Beedle, Matt. "Milankovitch Cycles and Glaciation," Glaciers with Time. http://www.homepage.montana.edu/~geol445/hyperglac/time1/milankov.htm. Website accessed on March 30, 2007.
Britt, Bruce. "Global Warming Could Spell Disaster For Blacks," BET.com. http://www.bet.com/News/global_warming_blacks.htm. Website accessed on April 1, 2007.(This article implies that natural disasters such as Hurricane Katrina are due to global warming and are somehow targeted at African-Americans.)
Bryson, Bill. A Short History of Almost Everything. Broadway Books (a Division of Random House, Inc.): New York, 2003.(Bryson's book is one of the most successful recent books on science for the general public.)
Colorado Research Associates. "The Maunder Minimum," The Convection Zone. http://www.cora.nwra.com/~werne/eos/text/maunder.html. Website accessed on April 2, 2007.
Columbia University Press. "Albedo," The Columbia Encyclopedia, 6th Edition. http://www.bartleby.com/65/al/albedo.html. Website accessed on March 31, 2007.
Greene, Robert, Alex Dudley, and Grey Evenson. "Sunspots and Temperature Correlation," Tropical Ecosystems. http://jrscience.wcp.muohio.edu/html/index.html. Website accessed on April 2, 2007.(This article summarizes the results of a study by the three Miami University of Ohio climatologists which shows that a period of high sunspot activity warms the atmosphere while a prolonged period of low sunspot activity leads to global cooling.)
Hadley Centre (U.K.). "Types of Climate Models," Met Office. http://www.metoffice.gov.uk/research/hadleycentre/models/modeltypes.html. Website accessed on April 3, 2007.
Kaplan, George. The Seasons and the Earth's Orbit. http://aa.usno.navy.mil/faq/docs/seasons_orbit.html. U.S. Naval Observatory website accessed on March 30, 2007.
Lear, Linda. Biography of Rachel Carson. http://www.rachelcarson.org. Website accessed on March 27, 2007.(Her loyal supporters claim Rachel Carson as the mother of the environmentalist movement in the U.S. She had an M.A. in zoology from Johns Hopkins University and for over a decade was the chief technical writer for the U.S. Fish and Wildlife Service. Her environmental treatise The Silent Spring signalled the beginning of the aggressive environmental movement we now have in the U.S.)
NASA. "Measuring Earthshine," NASA News Archive, July 9, 2002. http://earthobservatory.nasa.gov/Newsroom/NasaNews/2002. Website accessed on March 31, 2007.
Prescott, Bruce. "Southern Baptists Denying Global Warming," Mainstream Baptist. http://mainstreambaptist.blogspot.com/2007/03/southern-baptist-denying-global-warming.html. Website accessed April 1, 2007.
Rosenberg, Matt. "Milankovitch Cycles: Changes in Earth-Sun Interaction," About: Geography. http://geography.about.com/od/learnabouttheearth/a/milankovitch.htm. Website accessed on March 30, 2007.
Soden, Brian J., Richard T. Wetherald, Georgiy Stenchikov, and Alan Robock. "Global Cooling after the Eruption of Mount Pinatubo," Science (4/26/2002), pp. 727-710. U.S. Conference of Catholic Bishops. "Global Climate Change: A Plea for Dialogue, Prudence, and the Common Good," USCCB. http://www.usccb.org/sdwp/international/globalclimate.htm. Website accessed on April 1, 2007.
U.S. Geological Survey/Department of the Interior. The Great Ice Age. Pamphlet from U.S. Government Printing Office, 1992.
White, Nicholas E. "What is the Solar Cycle?" The Starchild Site. http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question17.html. Website accessed on April 2, 2007.
Wikipedia, "Albedo." http://en.wikipedia.org/wiki/Albedo. Website accessed on March 31, 2007.
_________, "An Inconvenient Truth." http://en.wikipedia.org/wiki/An_Inconvenient_Truth. Website accessed on March 28, 2007.(This entry is a discussion of Al Gore's book and the documentary made from the book. It attempts to be politically neutral, but does lean slightly left. To find any discussions of Gore's critics you have to read all the way to the end of the entry.)