The devastation of Hurricane Harvey has been all over the news. Not surprisingly, some have attempted to blame the storm on climate change.
The argument is inevitable and intuitive. It’s also a classic case of cherry-picking.
If you accept the general premise of climate change as I do, this may not be immediately obvious. It’s always harder to spot bad arguments when they support your position.
To see the flaw in the “Strong hurricane = climate change” line of reasoning, it’s useful to recall the familiar argument offered by skeptics whenever a particularly harsh winter comes around. That argument goes something like this: “See this super cold winter we’re having? Clearly, the planet is not warming up and climate change is a hoax.”
The proponents of one line typically have nothing but disdain for the other. (I should know; mocking the skeptic’s winter example used to be a hobby for me.) But in reality, the arguments are mirror images of each other. That’s bad news for both camps.
To be fair, the arguments each start from a kernel of truth. In the case of hurricanes, climate change entails higher global temperatures, which means higher average temperatures in the ocean. Higher ocean temperatures in turn mean more energy to be released in a potential hurricane. Higher average air temperatures also mean that the air can hold more water, resulting in more rain. Altogether, these forces should result, on average, in stronger, wetter (and perhaps more frequent) storms than would occur otherwise. I won’t pretend to be a climatologist, but this is the standard rationale and it seems entirely reasonable. I also haven’t come across many attempts to dispute it.
The underlying premise for the winter argument is simpler, but equally credible. Lower average global temperatures would tend to result, on average, in colder, harsher winters than would exist otherwise. Thus, in the extreme case of a glaciation period during an ice age, when global average temperatures are cyclically low, wintry conditions would have been particularly brutal and persistent.
The problem is that both of these weather patterns, hurricanes and winter, are subject to natural variation. Even if global temperatures stayed exactly the same, there would be no guarantee that the upcoming winter in my city would be the same as last year’s. On the contrary, it’s likely they would be perceptibly different. Global temperature levels may be one variable that influences winter conditions, but it’s not the only one.
So it is with hurricanes as well. Every hurricane is not alike; every hurricane season is not equally destructive. And even though global temperature and CO2 concentrations have been on a consistent upward trend in recent years, it is not the case that every successive hurricane season has been worse than the last. To state an obvious example, the hurricane season that took place after Hurricane Katrina in 2005 was comparably mild in the US.
The point here is that unusually strong hurricanes occur periodically due to natural variation; that’s why we have terms like a “500-year flood”. These types of storms have happened and would continue to happen with or without climate change.
What climate change does is to make the storms somewhat worse than they would otherwise be. That’s true enough, and experts debate exactly how significant the effect is. But obviously, this modest and nuanced statement is leagues different from saying “Harvey Is What Climate Change Looks Like” as a recent headline in Politico Magazine put it.
I realize it’s fashionable to never waste a crisis, but it’s probably a bad idea to adopt the fallacies of your opponents.