Rain - the most needed and least understood

kw: book reviews, nonfiction, rain, natural history, cultural history

Whew! Eleven days since I last posted. It scarcely ever takes me that long to read a book. I had high hopes from Rain: A Natural and Cultural History, by Cynthia Barnett, and they were fulfilled in part, but it was simply tough sledding to get through it all. I suppose I am not one who ought to criticize, given the length of some of my posts, and I remember the apocryphal story of the king telling Mozart, "There were too many notes." Mozart, puzzled, replied, "Majesty, which ones should I have left out?" Nonetheless, for the number of ideas conveyed, there were too many words.

An idea new to me, that stuck with me, is that significant shifts in rainfall—climate patterns—and the rise or fall of ancient empires happened in synchrony. Too many of these coincident trends have occurred for them to be "mere coincidences". Sustained drought destroys empires. The equable climate of the past 12,000 years has been a little longer than average for the era of Pleistocene Ice Ages. On average, warm periods are about 1/8 to 1/5 as long as cold periods, and only one other Interglacial Period of the last five, over the past half million years, was as long as this one.

Stepping back a thousandfold, we find that there has been no comparably cold period as the Plio-Pleistocene (the last 5+ million year) in the last 500 million years or so. The "average" climate of the Paleozoic, Mesozoic and Cenozoic eras was tropical warmth between the Arctic and Antarctic Circles, and ice-free poles. Ms Barnett takes us back another factor of eight, to the time four billion years ago, after the "Late Bombardment", when Earth's crust had cooled sufficiently for liquid water to exist on the surface, when it is supposed that great rains continued for a few million years to fill the oceans. The Bombardment itself probably supplied a lot of the water in the form of comets, which exploded to vapor upon impact, and whose vapor hung suspended in a thick atmosphere while the molten-rock surface gradually cooled. As an aside, I suspect the great amount of atmospheric water vapor acted as a thermal blanket and kept the surface quite hot, indeed, for a much longer time than a gas-free planet would have experienced. Venus shows us what happens if it never cools off, and when the water is replaced by carbon dioxide as a thermal blanket.

Well, back to civilizations. Cities are typically found along rivers. Rivers are fed by runoff from rain in the uplands and throughout the river's watershed. Up to a point, the river nourishes the city. But many of our cities have overgrown their rivers, and overuse them to the point that the polluted river turns around like the tiger, tired of its rider, to kill the city riding atop it. Think Cleveland and the Cuyahoga River. When our family moved to Cleveland in 1961, we took a sightseeing cruise on the river, where we were told the oil atop the river was four inches thick. When it caught fire in 1969, destroying many of the variously openable bridges, that was not even the worst of its fires. Before Cleveland's "city fathers" finally got up the gumption to clean up the river and do some proper sewage control, the river had burned 13 times since the 1890's.

You could say our civilization is in the midst of either learning to preserve the natural resources on which we depend, or collapsing to a level, both population and economically, that the tiger stops biting. But in this case, the tiger includes not just the rivers, but the atmosphere and the rain it produces, the great "river of wet air" that sustains us all. The last couple of chapters dwell firmly upon our contribution to climate change.

Rain is not what we think it is. We say, "Pure as the new-fallen snow". I could not find a similar proverb about rainwater, but we think of it as very pure. It's distilled, after all. But let us not forget the atmosphere through which it falls. Air is about 0.04% carbon dioxide (now, that is; it was 0.03% when I was a child). That is enough to shift its pH from 7 (ultra-pure water) to 5.6 (very mildly acidic). What else is in the air? It depends on where it has been. These days, most places on earth are downwind of some company's smokestacks. About half of those are putting sulfur or nitrogen oxides—or both—up into the air. Add moisture to them and you have acids a lot stronger than carbon dioxide. Some of the resulting acid rain has a pH in the 2-3 range. Strong enough to wipe the lettering from marble tombstones and statues over a few decades. Strong enough to kill all fish and frogs in thousands of lakes. Acid rain led to the Clean Air act in the USA in 1970, and to similar legislation in a few other countries. The pH now is mostly in the 3-4 range, at worst. That's not good enough, though.

But sometimes rain picks up other stuff. A chapter reports on the obsession of Charles Fort with odd rainfalls. Rains colored, red, brown, green or even black. Rains of frogs or fishes. Waterspouts can explain some of these. A red rain consisting of red-colored cells or cell-like spheres sometimes fall in Kottoyam, India. Then there's yellow rain: is it "agent orange" or a mixture of pollen and bee feces? The jury is still out on that one.

There are chapters on rainmaking and forecasting. Making rain only seems to work when you don't want it to work that well: in the few instances that it seemed to work well it caused devastation, such as in Rapid City, SD in 1972. We can forecast pretty well when it comes to temperature and wind direction, but not so much for rainfall. I recall a Meteorology professor telling about getting a call from someone saying, "Hey, Doc, I have about ten inches of your 'partly cloudy' lying in my front yard."

Ms Barnett visited various places famous for lots of rain, or for very little. In North America, the extremes are Death Valley and northwestern Washington; average yearly rainfall in the one is about 4 inches, and in the other, about 130. But worldwide, it's another story. Less than a tenth of an inch in some places in the Atacama Desert of Chile, and 450-500 inches in a very few spots, such as a mountaintop in Hawaii and a few towns in northeast India, including Cherrapunji. That town once received more than 1,000 inches of rain in a single 12-month period. Of course, Ms Barnett had to go there, and was rewarded with five days of fair weather! This in the middle of the Monsoon season.

So, there was a lot of fun to be had reading the book. I got bogged down in some long stretches, and I am too compulsive a reader to skim and skip. On the whole I am glad I read it.