As a scientist who has studied global climate change for more than 25 years and published many articles and a book on the subject ("Climate Change: Causes, Effects, and Solutions," 2003), I must take issue with the points made by Don Easterbrook published in "Whatcom View" April 14. The article typifies the use of selective half-truths chosen to support a pre-conceived idea, i.e. that humans are not having significant effects on the Earth's climate. For example, yes it is true that there have been multiple periods of warning over the past 10,000 to 15,000 years (since the last ice age). And, yes, at times it was warmer than the present. Yes, this happened before the rise in atmospheric carbon dioxide from the burning of fossil fuel.
What the author fails to explain (but surely knows) is that these warming periods are largely the natural result of the Milankovich Cycle, i.e. changes in the orbital configuration and distance between the Earth and sun that determines how much solar energy and consequent heat the Earth receives. These natural cycles happen slowly on periods of tens of thousands of years with temperature changes of plus or minus about 3 degrees Fahrenheit. Past global temperature variations are also related to natural variations in atmospheric carbon dioxide. Global temperature rose five degrees Celsius 56 million years ago in response to a massive injection of greenhouse gases into the atmosphere from volcanic activity.
Today, burning of fossil fuel is releasing greenhouse gases to the atmosphere at 10 times that rate. Indeed, it is the speed of today's human-caused temperature increase that is more troubling than the absolute magnitude, because adjusting to rapid climate change will be difficult. For example, the natural warming since the last ice age 18,000 years ago to about 1850 (the beginning of the industrial revolution) was about 5 degrees Fahrenheit or less than 0.0003 degrees per year. The average global temperature increase from 1850 until now has been almost 2 degrees Fahrenheit, or 0.0122 degrees per year - a rate 41 times faster than the pre-industrial warming.
The rapidly increasing exponential trend in warming from 1880 to 2011 can be clearly visualized in a time-lapse sequence produced by NASA and can be viewed online climate.nasa.gov (select interactives, then climate time machine) or at http://www.smartplanet.com/blog/thinking-tech/nasa-video-shows-global-warming-is-real/10021.
To use a local example, I asked students in one of my classes to examine February temperature records for Bellingham. They showed a clear and significant trend line where average February temperatures rose 5 degrees Fahrenheit from the 1920s to the 1990s.
Dr. Easterbook correctly notes that carbon dioxide makes up only a small percentage of our atmosphere. This does not mean it is irrelevant, in fact it shows just how powerful a greenhouse gas it is. If it were not part of our atmosphere our planet would be as cold as the surface of Mars. Its atmospheric concentration has increased by 37 percent since the beginning of the industrial revolution. He claims that "carbon dioxide accounts for only 3.6 percent of greenhouse warming." In fact, it is more like 9 percent to 26 percent and there are other greenhouse gases like methane, which also result from human activities, and water vapor (a major contributor), which is now increasing due to increased ocean evaporation from the warming itself (a positive feedback). He claims there is little or no relationship between carbon dioxide and temperature. Yet, more than 20 years ago scientists publishing in one of the world's most respected peer-reviewed journals, "Nature," stated that "The probability that the level of coherence between ...CO2 concentration and temperature is due to chance alone is about 2 out of 1 million."
I believe man-made climate change will ultimately prove to be the most important and costly issue of the 21st century.
ABOUT THE AUTHOR
Bellingham resident John T. Hardy is professor emeritus at Huxley College of Environmental Studies at Western Washington University where he taught a course on global climate change for 15 years. He is author of more than 100 publications. He is an elected fellow of the American Association for the Advancement of Science, and former program director of the Ecological Effects of Stratospheric Ozone Depletion for the U.S. Environmental Protection Agency. He suggests for further information you go online to climate.nasa.gov.