Like most young people growing up in the 1940s and 1950s, I depended on National Geographic to satisfy my curiosity about the world around me. It was a major reason why I chose a career in science.
So I was disappointed to see the great magazine of my youth compromise its reputation recently by taking an obviously politically motivated position on the issue of global warming. For me this fall from grace was tantamount to the time long ago when I learned the truth about Santa Claus.
Regional, Anecdotal Data
National Geographic‘s September issue contains a lavishly illustrated 74-page feature on climate change that focuses entirely on bits and pieces of data that seem to support the theory that human activity is causing global warming. No mention is made of the many prominent scientists who say we know too little to make this attribution or to predict future climate change.
On a global level, when all the Earth’s ice is measured, we find as much is currently thickening as is thinning. Similarly, when we ignore short-term regional trends and focus on global temperatures as measured by satellites, no warming trend is found. We have plenty of anecdotes that seem to suggest a trend toward climate change, but little evidence or proof that warming is happening on a global scale or that mankind is responsible for it.
Small Increase in Greenhouse Gases
The gases that absorb infrared radiation from the sun and create the greenhouse effect are mainly water vapor, carbon dioxide, methane, and nitrous oxide. Water vapor and water in clouds absorb nearly 90 percent of the infrared radiation, while carbon dioxide, methane, and the other minor greenhouse gases together absorb little more than 10 percent of the infrared radiation.
Therefore, most of the greenhouse effect is natural and caused by the different forms of water in the atmosphere. However, human activities over the past 100 years–such as burning wood, coal, oil, and natural gas–have increased the concentration of greenhouse gases in the atmosphere by an amount equivalent to a 40 percent increase in carbon dioxide alone. This is an increase of only 2 percent in total greenhouse gases.
Most Warming Preceded Rise in CO2
The average global temperature of the Earth has increased roughly 0.6ºC over the past 120 years. Much of the observed temperature rise occurred before 1940, whereas most of the additional carbon dioxide (more than 80 percent) entered the atmosphere after 1940. Obviously, human activity cannot be blamed for a temperature rise that occurred before the major increases in these gases occurred.
From 1940 to 1970, carbon dioxide built up rapidly in the atmosphere. According to the simplistic reasoning of the alarmists, the temperature of the Earth should also have risen rapidly. It did not.
When scientists analyzed the relationship between atmospheric CO2 levels and temperatures dating back 250,000 years, inferred from ice cores drilled in Greenland and the Antarctic, they found that sometimes the concentration of CO2 was high when the temperature was low, and sometimes the CO2 was low when the temperature was high. (1)
Blame it on the Sun
So what drives global climate, if not greenhouse gas concentrations? Well, maybe it’s the sun.
There are three variables affecting the Earth’s orbit–orbit shape, tilt, and wobble–which profoundly affect weather patterns. The Earth’s orbit does not form a circle as it moves around the sun–it forms an ellipse, passing further away from the sun at one end of the orbit than it does at the other end.
During a 100,000-year cycle, the tug of other planets on the Earth causes its orbit to change shape. It shifts from a short, broad ellipse that keeps the Earth closer to the sun, to a long flat ellipse that allows it to move farther from the sun and back again.
At the same time the Earth is orbiting, it also spins around an axis that tilts lower and then higher during a 41,000-year cycle. Close to the poles, the contrast between winter and summer is greatest when the tilt is large. The Earth wobbles because it is spinning around an axis that tilts back and forth. Thus, a temperature drop occurs in the Northern Hemisphere when it tilts away from the sun; then the same thing happens in the Southern Hemisphere and again in the North, in a 22,000-year cycle.
We know from simple physics that the additional energy added to the climate system by the doubling of atmospheric CO2 is about four watts per square meter (W/m2)–a very small amount of energy when compared to the 342 watts per square meter added by the sun’s radiation at the top of the atmosphere, and small also when compared to natural variations in the amount of radiation the sun sends toward the Earth.
The possible increase in energy stored in the atmosphere due to human activity is also small when compared to uncertainties in the computer simulations of the Earth’s climate used to predict global warming. For example, knowledge of the amount of energy flowing from the equator to the poles is uncertain by an amount equivalent to 25 to 30 W/m2. The amount of sunlight absorbed by the atmosphere or reflected by the surface is also uncertain, by as much as 25 W/m2. Some computer models include adjustments to the energy flows of as much as 100 W/m2. Imprecise treatment of the effect of clouds may introduce another 25 W/m2 of uncertainty into the basic computations. (2)
These uncertainties are many times larger than the four W/m2 input of energy believed to result from a doubling of CO2 concentration in the atmosphere. It is difficult to see how the climate impact of the four W/m2 can be accurately calculated in the face of such huge uncertainties. As a consequence, forecasts based on the computer simulations of climate may not even be meaningful at this time.
No Need to Panic
But suppose the computer models, for all their flaws, somehow turn out to be correct. Suppose the anecdotes about glaciers melting, butterflies changing their migration patterns, and so on all do point to global warming. What should we do?
Even assuming the worst-case scenarios, delaying substantial cuts in CO2 emissions for the next 25 years would produce an additional global temperature rise of no more than a few tenths of a degree C by the year 2100. (3) That means we have at least 25 years in which to sharpen our understanding of climate, seek more accurate predictions, and find new technologies to address the alleged problem. With the U.S. federal government alone spending some $3 billion a year on climate change research, it would seem to be a sure bet that our knowledge will be much more complete a quarter-century from now.
If an incremental warming of a few tenths of a degree, spread over decades, should in fact occur, it would constitute no hazard to ecosystems or human well-being. Economists and agricultural scientists say it would probably be beneficial. Hence, given all of these variables, policies made in haste or based on poor information are likely to have a destructive impact on the U.S. and world economies and the well-being of their citizens.
National Geographic‘s decision to present only the alarmist perspective on this important issue means it missed an opportunity to truly educate its readers. Most of us laughed at the absurd science fiction displayed in this summer’s global warming movie, “The Day After Tomorrow.” Seeing similar mistakes and exaggerations appear in a respected and influential magazine is no laughing matter.
Dr. Jay Lehr ([email protected]) is science director of The Heartland Institute.
(1) H. Fischer and M. Wahlen, “Ice Core Records of Atmospheric CO2 Around The Last Three Glacial Terminations,” Science 283, 1712-1714 (1999).
(2) R.D. Cess, M.H. Zhang, P. Minnis, L. Corsetti, and E.G. Dutton, “Absorption of Solar Radiation by Clouds: Observations Versus Models,” Science 267, 496-499 (1995).
(3) T.M.L. Wigley, R. Richels, and J.A. Edmonds, “Economic and Environmental Choices in the Stabilization of Atmospheric CO2 Concentrations,” Nature 379, 240-243 (1996).