Widening Tornado Alley

A new study out of Stanford and Purdue is one of the latest in a long line of research looking at how global climate change will affect the world’s weather systems, and in particular, how it will affect highly destructive storms. With such catastrophic hurricanes as Sandy and Katrina still fresh in our memories, not to mention the inevitable destruction that sweeps through the Midwest every spring when tornado season hits, it is easy to understand why we should be concerned with the possible connection between climate change and dangerous weather. What the study found echoes what we have been hearing for quite some time now, from a variety of different sources (not just hard science either, even National Geographic had an issue on how rising waters will affect hurricane season just last month). As global climate change (often referred to as global warming) continues, we will see an increase in the number of severe thunderstorms and the frequency of dangerous conditions (i.e. conditions which lead to events like hail storms or tornadoes).

A tornado touching down in South Dakota (Source: science.nationalgeographic.com)

The group used a multi-model system called CMIP5 (short for Coupled Model Intercomparison Project, Phase 5) to examine how greenhouse gas accumulation will impact weather patterns across the United States. Their models predicted how many days each year would have suitable conditions known to lead to destructive weather. They found that as temperatures continue to increase, we will see more and more days primed to host dangerous storms. The increased temperatures will lead to a general increase in what climatologists call Convective Available Potential Energy (CAPE), which is used as an indicator of atmospheric instability. The higher the CAPE, the more unstable your weather can become, and thus the more dangerous. At the same time, they found that those forces which would inhibit dramatic weather changes would decrease, meaning that all of the potential catastrophe building as CAPE increases would be more able to become actual catastrophe, in the form of high winds, severe thunderstorms, and tornadoes.

Maps showing the change in CAPE in each season during the late 21st century. The top map is winter, the second spring, the third summer, the fourth fall. Deeper reds imply greater increase in CAPE, and thus more unstable weather conditions (Source: http://www.pnas.org)

The group analyzed seasonal change as well, keeping track of how many possible storms cropped up in each season as temperatures shifted. They found that across all models, both spring and fall would see an increase in the mean number of days suited for some serious weather. This is particularly disheartening because, once again across all models compiled, these changes would be arising within the first half of the 21st century. So according to their results, we should begin seeing significant increases in spring and autumn storm severity by 2050. That’s some pretty heavy news when you think about it, especially given how destructive our current storms already tend to be.

As I said, this is just one more study in an increasingly long line trying to determine what will happen to our weather should climate change continue unabated. The study has a strong, convincing result, with personal connections for anyone who has grown up in an area affected by serious weather (myself included). Yet as usual, findings like this will be contested, the cause of climate change will be questioned, and the move towards some degree of self preservation will undoubtedly halt, mired in some stagnant political debate no one cares much about. Not being a climatologist or a glaciologist or even an oceanographer, I cannot say whether or not global climate change is definitively the fault of humanity or if it is just a natural process we are only now discovering. But the general scientific consensus certainly seems to weigh heavily in the favor of it being our doing. And, as I have said before, can we really afford to bet that it’s not us? Are we really willing to put our own future, our planet’s future, against the odds, just to avoid some effort to change? Because if so, that’s really very sad.

Original article: http://www.pnas.org/content/110/41/16361.full


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