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Monday, Jan 16, 2017

Cold spell near? Geologist digs deeper on climate change

On the climate-change front the forecast would seem to be increasing cloudiness.

At least that’s the impression a rational observer would get from the latest report from the United Nations’ Intergovernmental Panel on Climate Change. True, the report does declare that “there is very high confidence that models reproduce the general features of the global and annual mean surface temperature changes over the historical period, including the warming in the second half of the 20th century.”

But that would appear to be the only thing the panel remains confident about.

Chapter 2 of the report expresses “low confidence regarding the sign of trend in the magnitude and/or frequency of floods on a global scale,” as well as “in observed trends in small-scale severe weather phenomena such as hail and thunderstorms.” Conceding that “conclusions regarding increasing global trends in drought since the 1970s were probably overstated,” the report says that “in summary, confidence in large-scale changes in the intensity of extreme extra-tropical cyclones since 1900 is low.”

That’s not all. According to figures last year from Britain’s Met Office, based on data from 3,000 measuring points around the world, on land and sea, there has been no discernible rise in global temperatures since 1992. According to the National Snow and Ice Data Center, the Arctic ice sheet increased by 533,000 square miles over the summer, to a size roughly half that of Europe.

What to make of this? Well, we laypersons can’t make much of it at all, because we lack the knowledge to place the data in context. Luckily, for those really interested, a solution is available. It is a book called “The Whole Story of Climate: What Science Reveals About the Nature of Endless Change” (Prometheus Books). The author, E. Kirsten Peters, is a geologist who says that what people are likely to have gleaned from media reports on climate change is “only one isolated part of a much longer and richer climate story.”

Climate science, with its computer models, is a Johnny-come-lately to the narrative. Not so geology. “For almost 200 years,” Peters writes, “geologists have studied the basic evidence of how climate has changed on our planet.” They work, not with computer models, but with “direct physical evidence left in the muck and rocks.”

Space constraints preclude any detailed summary of Peters’ accessible but jam-packed little book. But some take-aways can be noted.

The first thing to note is that we could be long overdue for a cold spell. In recent geologic history, which stretches back a couple of million years — geologists have an expansive view of time — Earth’s climate has been characterized by long periods of bitter cold punctuated by brief episodes of warmth. “The cycle,” Peters notes, “is always a long period of cold followed by a much shorter period of warmth.” Specifically, the cold intervals last about 100,000 years, and the warm ones about 10,000. The period we are living in, called the Holocene, began 11,700 years ago, which makes it “no different at all from other brief, warm intervals in the Pleistocene,” the previous epoch that lasted those couple of million years.

Peters uses the analogy of a football field to help visualize all this. We in the Holocene are positioned at the edge of one of the end zones. The cold periods average about 5.5 yards, the warm ones about half a yard.

Another point Peters is at pains to emphasize is that climate change can be quite abrupt. Toward the end of the Pleistocene Epoch, northern Europe experienced a period of warming called the Allerod Oscillation that lasted about 1,000 years. The pollen record indicates that the “shift to renewed bitter cold took place very rapidly, certainly within a single human lifetime.”

Most of the publicity on climate change has focused on temperature, but precipitation patterns can be deeply worrisome, as well. The prelude to the so-called Little Ice Age came in the form of torrential rains that swept Europe in 1316. By the 1340s “really cold temperatures” had arrived, as well. And, in our own Southwest, the entire Chacoan Pueblo civilization had disappeared long before the end of a 50-year period of drought that began in 1134.

Peters is by no means sanguine on human-generated carbon emissions. She’s quite specific: “ ... what non-geologists don’t generally know is that we have a major problem on our planet with coal fires that are unwanted and burning out of control,” and she points out that “the technical knowledge is in place to put many of them out; the main thing lacking is commitment.”

Frank Wilson is a former book-review editor of The Philadelphia Inquirer.