Up tornado alley
The first time I heard a tornado siren was during the first summer I spent in Indiana. Sitting alone in a computer room at first I ignored the wail in the background. Then a janitor came in and informed me the sound I was hearing was a tornado siren and I needed to get out of the building. Leaving the building didn’t sound like anything I really wanted to do (and in hindsight I think I misinterpreted–probably the janitor meant I should go to the tornado shelter, which was accessed by leaving the building) so I asked the first group of people I came across–a group of meteorology grad students–what I should do.
Instead of directing me to the safety of the basement or the tornado shelter, they took me to the roof observatory, where we watched the storm rage around us, hoping to glimpse a tornado but never spotting one.
I tell this story to make a couple of points: one, there are people who are crazy enough to actually want to see a tornado, and two, weather is a big deal in the midwest.
Most of my husband’s family lives in the midwest or the south. Over the last year my husband and I have gone from being related to nobody directly impacted by a tornado to being related to three families who’ve suffered significant property damage from tornadoes, two of them in the last week. Fortunately, nobody we know was hurt–only homes and businesses were damaged–but the same can not be said for at least 200 people across the southeast and midwest.
Being an Earth scientist watching natural disasters unfold is always a little strange. While the magnitude of human suffering is always heart-wrenching, the magnitude of the geologic event is almost never truly surprising, nor is the damage the Earth is capable of visiting on us. We live on an active planet–a good thing, since life would be less probable in the absence of plate tectonics and impossible without a hydrologic cycle. But while that activity sustains the biosphere, it causes the periodic cataclysms we find so distressing. The vigor of the rock cycle returns carbon dioxide to the atmosphere that would otherwise languish in solid form, but it also brings us earthquakes capable of leveling cities and spawning tsunamis that scour the land and intensify the damage from the shaking, as we saw both in Sumatra and more recently in Japan. The hydrologic cycle moves water from the salty oceans onto land, where it nourishes the ecosystems in which we live, but it does so in a very uneven fashion, producing everything from intense droughts to intense hurricanes, from gentle mists to thunderstorms and tornadoes.
We are familiar with the current patterns of weather and climate, with current patterns of tectonic activity. Having grown up in Utah I know snow falls in the winter and is mostly melted by the end of May, which means reservoirs are required to have water available through the rest of the year. I know Indiana is wet all year long, allowing even me with my brown thumb amazing (to me) success in the garden. Being a geologist, working on paleoclimate, I am also aware those basic weather patterns–dryness in the west and wetness in the east–have persisted through the last few thousand years.
Some aspects of the climate system don’t leave behind a good record geologists can use to reconstruct things like frequency or intensity. Tornadoes, for example, don’t leave a tangible, unambiguous signal in any geologic archive. Hurricanes can leave some signal of their passage, but the signal is far from unambiguous and probably misses smaller events. Lacking an archive to examine, Earth scientists turn to climate models to estimate changes in the behavior of the weather–changes in frequency or intensity of storms and droughts.
Attribution of extreme weather to climate change is difficult, though some attempts have been made. The problem is, there’s a lot of natural variability in the weather, so it’s nearly impossible to pin any given storm or drought, or weather event at all on climate change. Probably we’ll go years before there’s another storm of this magnitude, before there’s another Katrina. But those storms will come, and, instead of being once in a century storms, they’ll become two or three in a century, or once in a decade.
It’s a future that will probably only make my tornado-crazy friends happy.