Friday, May 24, 2013

Left Side of the Aisle #109 - Part 6

The Oklahoma tornado and global warming

The other thing I wanted to talk about in the wake of the Oklahoma tornado is the connection, if any, to global warming. Certainly, that has come up, as it inevitably will in the wake of any major weather event.

And the fact is, the evidence not only that global warming is real but that the effects are being seen already just keeps growing. For one example, according to a study by the UK's national weather service, known as The Met, which was published in March, human-driven global warming was one of the causes of East Africa's drought in 2011, making global warming one of the causes of a famine that killed tens of thousands.

Here's another: One prediction of the impacts of global warming is the spread of disease and we may already be seeing that here in the US, where there has been an 850% increase in the incidence of "valley fever" since 1998, with California and Arizona the worst hit. Valley fever is a painful, debilitating, and sometimes deadly disease contracted by breathing in fungus-laden spores from dust disturbed by wind or activity. A warming, drier, climate creates more dust more easily spread, carrying a fungus that is sensitive to environmental changes - and thus you have a spreading disease.

So back to Oklahoma and the tornado. Did global warming cause this tornado? No one can say. It's not scientifically possible to ascribe any individual weather event to climate change. That is, you can't say that if human-driven climate change wasn't happening, that such-and-such a storm or whatever would not have happened. You can, however, talk about likelihoods.

Climatologists are already predicting more extreme weather as a result of climate change. One example is hurricanes: The prediction is for fewer but more severe storms over time. The actual science involved is of course complex, but the logic is pretty straightforward: Heat is energy. A warmer climate means more heat and therefore more energy in the atmosphere and the oceans. Hurricanes draw much of their energy from the warm water over which they form, which is why they form in the tropics, where the water is warmest. Warmer air can hold more moisture than cooler air. Add that up and you have more energetic storms that can hold more moisture before releasing it, totaling hurricanes with more wind and more rain.

A similar prediction holds for blizzards and that does appear to be happening: the intensity of blizzards appears to be on the rise.

Tornadoes, however, are a different animal. There's a lot about tornadoes that meteorologists and climatologists still don't understand. But something that is known is that there are two main ingredients for making a tornado. One is an energy-building mix of heat and humidity. That will become more likely in a warming world. The other, however, is lateral wind shear; that's what creates the twisting air currents that are a tornado. And some researchers think that a warming climate is actually less favorable for lateral wind shear, which could actually reduce the number of tornadoes by making it harder for them to form. On the other hand, it could also mean that those tornadoes that do form will be of the most intense sorts.

As one researcher noted, if one factor for tornadoes is more likely and the other is a wild card, it's still more likely than not that the combination of the two will result in more tornadoes - but the bottom line is that it's still too early to tell.

So should we expect more hurricanes as the result of global warming? Yes. Should we expect more blizzards? Yes. Should we expect more droughts? Yes. Should we expect the spread of diseases such as valley fever? Yes.

Should we expect more tornadoes? We don't know yet.


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