(Cornwallalliance.org)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 www.drroyspencer.com:
http://www.drroyspencer.co
