Reality: The Earth does much of its business through extreme events. The reason that the Arctic and Antarctic aren’t even colder? And that the equator isn’t warmer? In the winter hemisphere, about half of the heat transport from equator to poles is accomplished by a procession of storms, strung like pearls across temperate latitudes. The source of much of the annual-average rainfall in the subtropics? Those dangerous typhoons and hurricanes. The trace chemical composition of the Earth’s atmosphere [the origin of those oxides of nitrogen, for example]? Lightning discharges, in any of the thousand or so thunderstorms underway at a given moment worldwide. That slow, centimeters-per-year, so-called “continental drift”? Riding on the Earth’s crust, we experience that drift as successive earthquakes and volcanic eruptions. In each instance, major global processes are manifested on the ground as highly-localized extremes.
The solid Earth and its oceans and atmosphere aren’t alone in working this way. Plants and wildlife do their much of their business through extreme events as well. Think about all the species of plants and animals that procreate suddenly, at a single time of year. In part this allows newborn to capitalize on plentiful food supplies. In part this suddenness allows the prey species to escape predation. So many are born that predators are unable to “staff up,” and small numbers of the young make it through, at every level of the food chain. [Seventeen-year locusts carry this strategy to the extreme.] Listen to the ecologists’ vocabulary! They speak of population explosions and collapse, disease outbreaks and pandemics – the language of extremes.
We humans do much of our business through extremes as well. Look at how we cluster tightly into major urban areas. Note the rhythm of our days (think rush hour) and of our years (think frenzied retail activity in the Christmas shopping season; the surge of vacationers each August). Consider the behavior of the world’s financial markets. Most of the gains and losses averaged over a decade come in just a few trading days. We don’t gradually start school, or finish school, or get married. You can think of your own additional examples!
How about the expression “When it rains it pours?” [This is true nearly everywhere, except maybe Seattle.] The hydrologic cycle is governed by extremes, cycles of flood and drought. But this bit of folk wisdom has always said something about the whole of the human experience, not just the weather, hasn’t it? Therefore, it is wrongheaded (and yet we do it) to think of extreme events as inherently unforeseeable, as suspensions of the laws of physics or the normal order of things. Extremes are the way things work. At least that’s true of “big” things. So, while a “tempest in a teapot” is an oxymoron – and therefore an irony, a tempest in the atmosphere is the norm.
[It’s even incorrect to see Earth’s extremes as inherently dangerous. Just one quick example: After construction of the Glen Canyon dam, motivated in part to reduce seasonal flooding along the Colorado River, Department of Interior scientists found that many of the ecosystems downstream had been dependent on those floods. To preserve these ecosystems, the Department had to artificially reintroduce such variability.]
Another point about these extremes; they’re integrative events. What does that mean? Just this…by and large, during the quiet interludes between extremes, the three big systems – the geophysical, the ecological, and the social – can be considered as isolated entities unto themselves, with the other two components of the Earth system as a backdrop. The extreme events are in the mathematical sense nonlinear [jargon alert!], and all three components engage. None can be considered by itself. Katrina, for example, was not just a geophysical event. It was not just a public safety event. It was also an ecological event, fundamentally affecting the Gulf coast’s wetlands, fisheries, etc. In the 1994 Northridge earthquake, almost ten percent of the fatalities resulted not from direct physical trauma but from an outbreak of coccidioidomycosis or desert valley fever. Aftershocks on the desert side of the mountains kicked up coccidioides spores and the prevailing winds carried them into the California’s Simi Valley.
Reality: What may be unlikely over any small interval of time at any particular location becomes inevitable as enough time goes by. The long recurrence intervals characteristic of many extremes contribute to the threat they pose. Societies and their institutions, both public and private, as well as individuals, contemplating the difficulties and costs inherent in mitigating against rare but high-consequence events (disasters), are frequently tempted to focus solely on more urgent daily matters – short-term business results and real estate development, etc. Most leaders in politics or business hope to muddle through – hope that they will experience no disaster while in charge. However, down the road, sooner or later, they or their successors will be forced to cope with a disaster on their watch.
The same reality applies to large numbers more generally. Years ago, when my statistician father was still alive, we were once taking a walk and talking when the subject turned to a piece in that day’s newspaper about a man who’d gone berserk and shot several people. My father observed, “You know, if you live in a small town, something like that is a real shock. But in a world with billions of people, those episodes are inevitable.” My dad said this at a time when people weren’t yet so concerned in the United States about terrorism, but I’ve thought about it often since 9-11. A low-level of terrorism is inevitable! The goal is not to eliminate it but to minimize it. I also thought about it during the evacuation in the face of Hurricane Rita (coming up on that five-year anniversary soon). A number of elderly died when their bus caught fire and burned. In an evacuation moving tens of thousands of people, such an event would be rare, but in an evacuation involving millions of vehicles, tragedies like this are bound to occur. Thus we can’t fixate solely on managing evacuations of ever-increasing geographic scale and complexity. Instead we have to make home the safest place to be (experts call this shelter-in-place; the policy has other benefits). By making it possible for people to stay put, we can reduce the scale and the risks of mass evacuations.
We’re getting ahead of ourselves, but this does segue into tomorrow’s post, where we’ll turn to some other social realities…