When meteorologist talk about a ‘500-year storm‘, they don’t mean a storm that occurs only once every 500 years. They mean a storm that in any given year has a 1:500 chance of occurring. There is no statistical correlation between the occurrence of one storm and another. The chance they will come 500 years apart or 5 days apart is the same. And so it is that right after hurricane Harvey devastated the Gulf coast, another category 4 storm, Irma, is barreling across the Caribbean toward the Florida coast. It is difficult to say whether this is just a fluke or a symptom of long-term changes in the global climate, since regular weather records have only been kept since 1880.
It is certain, however, that since 1880, the earth’s average global temperature has been rising at an increasing rate . Using the average global temperature in the 20th century as the point of reference, the average annual global temperature was below it until World War II. It was higher during the war, then frittered about either way until the mid-seventies. From then on it has risen continuously and ever more steeply. The last year cooler than the 20th century average was 1976. All in all, it is on average about 1.2ºF warmer now than 2 centuries ago.
Perhaps 1.2º does not make much difference if you’re used to 100º or higher, but it does make a lot of difference to the 326 million trillion gallons of water on Earth. If frozen solid, as two-thirds of it are, it will become liquid. If liquid, it will evaporate. The warmer it gets, the more water turns into vapor and the clouds get bigger and the rains heavier.
The oceans hold almost three quarters of the earth’s water. Cold water moves down and warm water moves up, leading to a complex dance between the water in the polar regions and the water at the equator. These swirls, in their turn, drive the prevailing winds. When the temperature balance in the oceans changes, so do the currents and the winds. Consequently, the clouds are not only getting bigger, but changing direction as well.
That means that areas that used to be dry are getting soaked and areas that used to be wet are drying out. The areas that used to be dry have no vegetation to hold the soil together, so that the rains will cause landslides and avalanches. The areas that used to be wet, on the other hand, have a lot of vegetation turning into fuel for wildfires.
(Note: The Pima County Department of Environmental Quality has issues an advisory on heightened levels of particulates drifting in from wildfires on the Pacific coast.)
The rise in global temperature corresponds to increasing levels of atmospheric carbon dioxide, which works like the roof of a greenhouse, letting a lot of sunlight in, but not much out. It is produced by burning carbon. Almost all living organisms generate energy that way. Plants do it only half of the time, miraculously reversing the process after sunset, but rootless creatures, like humans, do it continuously. It’s called breathing. Humans not only energize their bodies that way, but also the machines on which their dominance is based .
There have been other periods with raised CO2 levels, long before humans came about. The rise in temperature was comparable to what we are experiencing now. If the current warming trend also arises mainly from natural casues, it is unlikely we can do much about it. We’ll just have to weather it until it blows over in 10 or 20 thousand years or maybe a couple of million.
But humans are not ones to let nature take its course. We’re always trying to improve upon it and this is the biggest opportunity in the history of our species do to do so. We are powerless over the forces of nature. But we do have reasonable control over our machines. It would certainly not hurt to keep those from contributing to the problem.
We’ve been so clever so far, why stop now. We already have invented all kinds of ways to generate energy without all the fumes. All we have to do is make them cost-effective. It must also be possbile to scale down production a bit, considering the tremendous quantities of useless rubbish on the shelves of department stores. Those appear to increase in tandem with the temperature too. Or perhaps it is the other way around. Anyhow, we can certainly put a crimp in it, although it is hard to tell whether it will be enough to stabilize the weather again. But nothing ventured, nothing gained.
Of course, this is a very complex undertaking. It will require fundamental changes in the way we do business, in the way we live, and even in the way we think. The world’s leaders will have to show some deft helmsmanship to steer us through the changing currents. It should occupy them to the extent that they won’t have time to play with their rockets.
The Weekly Green is a KXCI mini-program on environmental topics from Southern Arizona and the rest of the universe.
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