Columbia Journalism Review‘s Curtis Brainard and I had a somewhat lengthy back-and-forth on Twitter about his view (10/30/12, 11/1/12) that some journalists and environmental activists are misleading the public by pointing to superstorm Sandy as an outcome of human-caused global warming. I argued on FAIR Blog (11/1/12) that saying that global warming caused Sandy is simply accurate–and later tried to make my point via tongue-in-cheek metaphor in a tweet.

I don’t think I convinced Brainard–“Wow. You’re spinning words like tops,” pretty much summed up his reaction. But I thought I’d try to explain what I was saying in a medium not limited to 140 characters–along with a better metaphor.

My argument was that climate change caused Sandy in the straightforward sense that without global warming, Sandy wouldn’t have happened. Weather is a chaotic system, meaning that small changes in initial conditions produce vast changes in outcome. We live on a planet where the atmosphere has been altered not slightly but dramatically by human actions, changing the climate and therefore all weather derived from the climate. Without climate change, Sandy wouldn’t be weaker or have a smaller storm surge or strike somewhere else; there would be an entirely different weather pattern, most likely an entirely unremarkable one.

This is not, I don’t think, the point climatologist Kevin Trenberth, quoted by Brainard, is making when he says, “All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be.” He’s saying that if you imagined Sandy without climate change, you would have a cooler, drier Sandy. What I am saying is that whenever you alter the conditions of the atmosphere in a significant way, in whatever manner, you will automatically end up with a different set of weather events–and the odds against these weather events without alteration would have produced something resembling Sandy are astronomical.

Believing that a Frankenstorm of some sort would have manifested itself in late October 2012 if people hadn’t started pumping carbon into the atmosphere in the 1800s is like believing that if chimpanzees instead of Homo sapiens had evolved into the dominant species on Earth, a chimp named Abraham Lincoln would have been elected president of the United States of America in 1860.

Now, you might say to me, “Yeah, yeah–so what?” One could argue that this kind of “cause” is trivial, because it applies equally to all weather events–that pleasant day in August, the first big snowstorm last winter, the lightning that hit the old barn two years ago–all these events were “caused” by climate change, in that the hypothetical world without climate change had entirely different weather events.

But I think it’s important to understand this about weather: There aren’t some weather events that are the result of climate change and some that aren’t. There are no weather events that are made better or worse by global warming. Without global warming, there would be an entirely different set of weather events.

What people think of as the interesting questions about climate change and extreme weather involve comparing the weather events we actually have with the weather on an imaginary Earth, where the climate hasn’t been altered by greenhouse gases. Would they have similar kinds of weather events there? More of some, less of others? More or less severe, on average? More specifically: Could the kind of storm that Sandy was have struck the East Coast at some point in time in a world free of global warming?

These are very hard questions to answer, obviously–since we’re unable to observe the weather on an imaginary planet–and scientists furiously debate the answers. I would note that if we’re talking about a weather phenomenon that’s never been seen before, we should be more skeptical of claims that such things happen naturally on hypothetical Earth X. And people who have been predicting that one of the things to expect from increasing climate change is an increase in the severity of storms should be listened to seriously when a storm of unprecedented severity occurs–just as people who recognized the housing bubble early on should have been listened to for advice on what to do after it popped.

But the one thing we can say for sure is that Sandy would not have occurred here and now without climate change. Is that a useful thing to say? Here’s a thought experiment: Imagine we live in that world with no climate change. (Maybe the industrial revolution developed with wind and water power until a Thomas Edison analogue invented the solar panel.)

In this world, researchers come up with a way to alter local weather. Some scientists warn against trying this out, saying that it could cause irrevocable changes to the climate, including severe storms. But the researchers say, no, while it will unavoidably randomize the weather all over the world, it won’t change the climate: You’ll get a different mix of weather after the alteration, but it will be the same mix of weather that existed before.

They go ahead and do the experiment–making sure, say, that there’s sunny skies over the Super Bowl–and then, within a year, a devastating hurricane wrecks Miami.

It’s hard to say how to answer the question of whether the experiment made the hurricane worse or not: It’s one data point, and one that could be found in an ordinary hurricane season–though it’s consistent with the prediction that the experiment would exacerbate storms.

But did the experiment cause the hurricane? In the sense that that hurricane would not have happened without the weather alteration, yes–the researchers are responsible for the hurricane striking Miami. That’s the way the courts would presumably view it, and that’s surely how the newspapers on Earth X would report it.

I put it to you that this Earth’s media ought to give the same treatment to the consequences of the real-world experiment we call global warming.