Exposing PseudoAstronomy

December 19, 2008

Record and Unusual Snows and Cold – Proof Against Global Warming?


It seems as though every winter now for the past few years, there’s some report of record snowfall or cold temperatures. Last year it was snow in Baghdad for the first time in a century. This year it just snowed in Las Vegas, NV and we have record cold in New England.

And, for the past few years, whenever this has happened we have had global warming deniers clamoring to say that this is proof that not only is man-made (anthropogenic) global warming not true, but global warming period is not true. And predictably, this has happened in the last few days.

I haven’t yet written a post focusing on global warming in this blog, and I don’t really intend to concentrate on it – this is more of an astronomy blog. However, as an astronomer/geophysicist as well as someone sharpening my teeth on instances of bad logic, I wanted to address this issue at least once.

Logical Fallacies

There are two main logical flaws here that I want to address – correlation without causation, and anomaly hunting.

The basic idea behind confusing a correlation (or association) with causation is that because two or more things seem to fit together (they look alike, they happen at the same time, etc.), then they must be related. For example, under this fallacy I would assume that if I turn on my computer and the doorbell rings, then me turing on my computer caused the doorbell to ring.

It should be noted that things that are correlated sometimes really are due to a cause and effect. In that above example, if I turn on my computer and I hear the Apple start-up chime come from my computer’s speakers, then those two correlated events really are causally connected.

The point of the fallacy is that you cannot – and should not – always assume that just because things are associated then they are connected.

The other fallacy is anomaly hunting, where you search for anything that will support your cause out of a vast array of information that doesn’t support your cause, and then use that as proof that your cause is correct. This is very often used in conspiracy theories – such as the Apollo Moon Hoax or even the September 11, 2001 terrorist attacks – and since the anti-global warming movement has by this point adopted many of the tactics of conspiracy theorists, it is no wonder that this fallacy abounds in their arguments.

What Global Warming Actually Is

The theory of global warming is that, over time, and on average, Earth’s temperature increases. Pretty darn simple. This is also referred to as “climate change.” And this terminology is key: When I took an intro weather geology class in undergrad, I was hammered on two vocabulary words that are often used interchangeably but really mean very different things: Weather and Climate.

Weather is the condition of Earth’s atmosphere at a given time and place, including such things as density, pressure, humidity, and temperature. Climate is the weather patterns over a long period of time. I hope by this point you can see where this post is headed — tying together three threads: Correlation is not causation, anomaly hunting, and weather is not climate.

Now the question is – what would happen if the overall temperature of Earth went up by just a few degrees? Well, the obvious answer is that things would be warmer. But this is NOT the only consequence. A result of areas becoming warmer is that weather patterns can change. Regions of Earth that once got plenty of rainfall could see that diminish, and vice versa. In addition, the overall warming can lead to more extreme weather patterns, including colder weather in some places during the winter. Just a few small changes in the jet stream over North America can easily bring cold air from over Canada down into the lower 48 states.

Why An Abnormally Cold Winter Does Not Sound the Death Knell for Global Warming

Let’s go in reverse order. First, these nay-sayers are focusing on weather events and are not looking at overall climate. Overall climate does show a trend of increased temperatures tightly correlated with atmospheric carbon dioxide concentration over the last few decades.

Second, they are assuming, effectively, an anti-correlation here, saying that this abnormally cold weather is the effect of global cooling, far from global warming.

And third, they are anomaly hunting, searching for the few events of cold weather or snowfall amidst an incredibly large amount of data that show evidence of global warming, such as the afore-mentioned actual temperature tracking, shrinking glaciers, and longer term temperature tracking from ice core samples and tree rings.

Final Thoughts

I hope that this post has fairly clearly shown that snow in Baghdad does not prove that global warming is a vast conspiracy propagated by leftist media and liberal scientists. I have no desire, here, to get into the politics of global warming nor really consequences — I simply want to show that the cold weather that global warming deniers use as evidence against it are really missing the point in three main ways.


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