What Past Climate Changes Reveal about the Current Threat—and How To Counter It
Wallace S. Broecker
New York: Hill and Wang, 2008
Skeptics often find a strange solace in the knowledge that climate varies naturally, as if that somehow disproves the fact that we are rapidly changing it ourselves, or as if it somehow implies that climate change is inevitably benign. When you have explored the Ice Age for as long as Broecker has, and especially the wild swings that happened within the Ice Age, you don't think natural climate variability is benign.
– Page xvi
Those of us who live in California have perforce become familiar with the reality of drought. The same is true for many other places in the American West. I have lived in cities when water was rationed there, and may again this summer (though a spate of late-season rainstorms lessens the certainty of that.)
But the inescapable fact is that much of California, and much of the region west of the Rockies, is arid or semiarid. Climate varies naturally. Rainy periods and periods of drought come and go. This has always been known. But only now are we learning exactly the historical pattern of those natural variations. The book quotes the words of Scott Stine, who has been researching the history of California climate through proxy data for twenty-five years or more:
"Here in California, we have built the most phenomenal urban and agricultural infrastructure of any place in the entire world," he says. "And we've done it since gold was discovered in 1848. The infrastructure is based on water, on storing water, on diverting water—I mean, most of the state is semiarid. And we've built it on the assumption that climate will continue to be as it has been since the gold rush.
"But at Mono Lake and elsewhere, we can document that the past one hundred and fifty years have been aberrantly wet—some of the most aberrant precipitation conditions that we've seen in ten thousand years. So we've built this system, in a sense, on a chimera. The climate record shows that California is subject to extreme and persistent droughts, which would just throw the whole system and the whole infrastructure for a loop."
"Now, fifty or sixty percent of normal precipitation—that's a strident drought. If it were to hit California and persist, year after year after year, there would be changes. But when I get up into these montane lakes—I can't get these lakes down to their medieval levels with fifty percent precipitation. It requires a far, far more strident drought than that. They've always scared me—they're telling us that precipitation gets down to twenty-five percent of normal and stabilizes at that for a long period of time. And to tell you the honest-to-goodness truth, I've always had a hard time believing that. The evidence is there, it's slapping me in the face. But, Jesus Christ, what a drought! Maybe I don't want to believe it."
– Scott Stine, Pages 171-172
What Stine and other researchers are discovering is that we built up California to a population of 36 million plus during a climate anomaly — a period when rainfall was unusually frequent and plentiful. That period is bound to end, just in the natural course of events. But we may in fact be advancing the timetable, by dint of our burgeoning industrial activity and population.
It's not news that America's western states are short of water. But if we enter what researchers have come to call a megadrought — one that lasts for decades or centuries — it will call for solutions of a whole 'nother level. As pessimistic as it sounds, I would not rule out actual water wars, not unlike the range wars of pioneer days. Consider these paragraphs from the book:
"As we write this, in the spring of 2007, the drought that began in 1999, and was interrupted in 2005 by a year of near normal rainfall in the West, seems to have returned. In March 2007, the runoff from the Colorado and other rivers into Lake Powell was a little above half of normal. In the first week of April, The New York Times reported on its front page on the various water projects—and water conflicts—that were taking shape as the West faced the prospect of a more arid future with a growing population. Utah was planning a $500 million, 120-mile pipeline from Lake Powell to the boomtown of St. George. Nevada was opposing the pipeline, but was planning one of its own to deliver water to Las Vegas from northern Nevada and Utah—which was of course fighting that project. In California on April 1, the Sierra Nevada snowpack was at only 42 percent of the long-term average, its lowest level since 1988, and state hydrologists are forecasting that the total runoff for the year would be only half of average. Governor Arnold Schwarzenegger was promoting a $4.5 billion bond issue to build more reservoirs. All seven Colorado Basin states—Wyoming, Colorado, Utah, Nevada, New Mexico, Arizona and California—were negotiating with the federal government about what to do once the day comes when there is no longer enough water to be divided up in the way foreseen by the 1922 compact. Meanwhile the eight states bordering the Great Lakes were attempting to negotiate a regional compact of their own; its main purpose was to protect their vast store of freshwater from any attempts to grab it, for instance by the booming Southwest.
– Pages 182-183
Subsequent paragraphs describe the work of Richard Seager and colleagues, who ran eighteen different climate models using the IPCC's "middle of the road" conditions. The results: all but one of the models indicated that a long dry period has already begun, and that by 2050 the southwest will be as parched as the Dust Bowl of the 1930s.
Now skeptics may claim this is just another case of computer models being used to foster alarmism. Tell it to the Anasazi, the Maya of Yucatan, the Tiwanaku of Bolivia.1 Analysis of proxy data confirms what historians had suspected: These civilizations were all wiped out by prolonged spells of drought.2 Say what you will about the reliability of computer climate models; but they are not the only way to derive this warning. It comes through loud and clear, if not so precise, in the conclusions reached by old-fashioned "slogging and logging" — field collection and analysis of samples.