Anthony Watts wrote down a nice table describing which folks believe or at least pretend to believe that CO2 "caused" Hurricane Sandy and which people don't. If I simplify it a little bit, activists, liars, and crackpots such as Al Gore support the link while scientists don't. I am kind of pleased to see that for the first time, most of the media seem to agree that the people promoting the hurricane-CO2 link are hacks.
I was intrigued by a member of the former group, hardcore leftist activist Mr George Lakoff, who wrote the following text for the Huffington Post:
He introduces a new problematic term: "systematic causation". He believes that fossil fuels "systemically caused" Hurricane Sandy (and other weather events we don't like). The description makes it look like the construct "A systemically caused B" means "A increased the odds of B" – note that my alternative wording is equally long, much more accurate, and not requiring any new contrived phrases.
Except that Mr Lakoff believes that AIDS is only "systemically caused", not "directly caused", by the HIV virus. That's pretty interesting. Either he is an HIV denier or his definition of "systemic causation" is internally inconsistent. But let's ask two questions: Was Sandy "systemically caused" by CO2 emissions? And forgetting about the answer and focusing on genuine "systemic causes" of bad events in general, is it legitimate for the society to outlaw them?
My answer to both questions is No, although the latter question deserves a subtler discussion.
Unless you believe in astrology and similar things, you will surely agree that it's not in the power of CO2 or any other indirect hypothetical causes to adjust some "highly internal" and "seemingly random" characteristics of tropical storms such as the population of the city that the storms target. ;-)
So the fact that Sandy managed to flood some tunnels in the New York subway system, among dozens of related achievements, is pretty clearly a coincidence that can't be explained by any well-defined long-term "cause", not even a "systemic cause". Most hurricanes avoid New York, some hurricanes get there, and only the proportion may be measured or theoretically calculated. In other words, when we talk about unknown future hurricanes, we may only predict their ability to target New York or other great cities probabilistically. And we may only estimate the probability that the most important hurricane of 2013 will make landing at most 4 days before the Halloween.
(The same comment, "only probabilistic predictions are possible", obviously applies to earthquakes in Italy, too.)
Needless to say, exactly the same words apply to Katrina and New Orleans in 2005. Katrina was a big story – much bigger than Sandy (surely by the number of casualties) – because it hit a large and relatively vulnerable city of New Orleans. Sandy was a relatively big story because it affected the "greatest city in the world" although not as much as Katrina did harm New Orleans. Let's agree that the targeting is a matter of chance.
But if you subtract all the "special characteristics" of Sandy that are related to its random path, there is almost nothing left. In fact, by the Accumulated Cyclone Energy (ACE), Sandy isn't even the largest storm of the 2012 Atlantic hurricane season. It's not even the second one. It's not even the third one: Sandy is just the fourth largest Atlantic tropical storm of 2012. That shouldn't be shocking because it has made it to the Category 2 and only marginally and for a short time.
One may look for various detailed properties of Sandy – its trajectory, its area, its pre-Halloween timing, and so on. But I think it's clear that trying to attribute some "message" (I would say "divine message") to any of these detailed properties is a sign of medieval superstitions. People who try to interpret these properties as divine signals may use a quasi-scientific vocabulary but the vocabulary isn't the essence. The essence is the logic behind their thoughts and beliefs and it is equally unscientific as any other generic medieval superstitions.
The fact that Sandy went to New Jersey is a coincidence – one that could be predicted a few days in advance but one that has no implications for any knowledge or mechanisms that are relevant outside the end of October 2012. The fact that Sandy hit before the Halloween or before the U.S. presidential election is another coincidence. It's totally scientifically implausible to assign "causes" or "systemic causes" to such microscopic accidental characteristics of a tropical storm. Such links are equivalent to astrology and other superstitions. There isn't any conceivable natural mechanism that could impose such causal links – and there's even no conceivable mechanism or explanation that could significantly increase the chance that a hurricane is more Sandy-like if the CO2 concentration is higher. I am convinced that everyone who has been given basic scientific education – or who has a basic scientific intuition even in the absence of any formal education – must know that.
So we are back to the usual questions whether the carbon dioxide in the atmosphere may be increasing or decreasing the number or hurricanes or their average or maximum intensity. I think that the data speak a clear language: no such dependence, whether positive or negative, may be extracted from the data that seem to be fully explainable by "noise", essentially "white noise". In the future, the datasets will become more extensive and perhaps more accurate and people may see a signal we don't see today. That's why it makes sense to ask whether we may predict what they will see. I think (based on arguments I have been repeatedly explained by Richard Lindzen in particular) that if they will ever see such an impact, it should be a negative impact – fewer hurricanes or weaker hurricanes. It's because storminess and other activity is driven by temperature (and other) gradients and in a hypothetical warmer world, the equator-pole temperature difference should be smaller because the poles should warm up faster. The gradients should decrease and because the gradients power the cyclone activity (and other things, including temperature variations in general), the cyclone activity should go down.
That's my prediction but I don't know how strong the effect is. It's probably very weak and it may remain invisible for centuries and perhaps forever because "global warming caused by CO2" will most likely never have an observable effect that would go beyond a modest shift of the global mean temperature.
Even when you look at the 2012 Atlantic hurricane season which became another heavily overhyped one, you will see that the Accumulated Cyclone Energy is just 121 so far, just marginally higher than the historical average around 105. The ACEs for individual seasons are never constant. They belong to some statistical distribution. It's inevitable that sometimes, the ACE ends up being above the average, sometimes (in many years after 2005), it ends up being below the average. There's nothing shocking about either outcome: it's a law of physics that such things are not constant although left-wing, egalitarian activists often have a problem with this totally basic concept underlying all of science.