Did Global Warming Cause Hurricane Sandy?

I’ve been trapped in post-storm hell (no power, no heat for 10 days. Now power is back, but still no internet at home, which is frustrating, but no big deal), and so I haven’t been able to post this until now.

I’ve been getting a bunch of questions from people in response to an earlier post of mine about global warming, where I said that we can’t blame specific weather events on global warming. The questions come down to: “Can we say that hurricane Sandy and yesterday’s NorEaster were caused by global warming?”

I try to be really careful about things like this. Increasing the amount of energy in the environment definitely has an effect on weather patterns. But for the most part, that effect is statistical. That is, we can’t generally say that a specific extreme weather event wouldn’t have happened without global warming. We can just say that we expect extreme weather events to become much more common.

But what about hurricane Sandy?

Yes, it was caused by global warming.

How can I say that so definitively?

There were a lot of observations made around this particular hurricane. What made it such a severe event is a combination of three primary factors.

  • The ocean water over which it developed is warmer that historically normal. Warm water is, simply, fuel for hurricanes. We know this from years of observation. And we know that the water was warmer, by a couple of degrees, than it would normally be in this season. This is a direct cause for the power of the storm, for the fact that as it moved north, it continued to become stronger rather than weakening. Those warm waters are, by definition global warming: they’re one of the things we measure when we’re measuring global temperature trends.
  • Hurricane Sandy took a pretty dramatic left turn as it came north, which is what swept it into the east coast of the US. That is a very unusual trajectory. Why did it do that? Because of an unusual weather pattern in the Northeast Atlantic, called a negative North Atlantic oscillation (-NAO). And where did the -NAO come from? Our best models strongly suggest that it resulted, at least in part, from icemelt from Greenland. This is less certain than the first factor, but still likely enough that we can be pretty confident.
  • Hurricane Sandy merged with another weather front as it came inland, which intensified it as it came ashore. This one doesn’t have any direct relation to global warming: the front that it merged with is typical autumn weather on the east coast.

So of the three factors that caused the severe hurricane, one of them is absolutely, undeniably global warming. The second is very probably linked to global warming. And the third isn’t.

This is important to understand. We shouldn’t make broad statements about causation when we can’t prove them. But we also shouldn’t refrain from making definitely statements about causation when we can.

The NorEaster that we’re now recovering from falls in to that first class. We simply don’t know if it would have happened without the hurricane. The best models that I’ve seen suggest that it probably wouldn’t have happened without the effects of the earlier hurricane, but it’s just not certain enough to draw a definitive conclusion.

But the Hurricane? There is absolutely no way that anyone can honestly look at the data, and conclude that it was not caused by warming. Anyone who says otherwise is, quite simply, a liar.

19 thoughts on “Did Global Warming Cause Hurricane Sandy?

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  2. Intelligent Design

    Exceedingly rare event only coming by the product of intelligent life’s intervention in the world. How are you not making the case for ID?

    1. MarkCC Post author

      Because there is no evidence for ID?

      There’s a big, obvious difference between warming and ID.

      In the case of warning, what we see is a specific change in the environment, which has a predictable effect. The effect is one that we can model with a high degree of accuracy, producing predictions that can be tested against real-world observations for accuracy. The theory works; it describes reality well; it makes accurate predictions; it works via a mechanism that we can understand and test.

      In the case of ID, there’s an ill-specified theory that evolution couldn’t have produced the observed world without intelligent intervention. Intelligent intervention is left completely undefined. The theory makes no testable predictions. The evidence cited in support of ID dreadful – in every case that I’ve looked at, it’s either fabricated (for example, the numerous out-of-the-ass probability arguments), nonsensical (CSI), erroneous, or poorly interpreted. Meanwhile, real evidence that we can observe suggests strongly that no intervention is necessary.

      ID is totally unnecessary to explain what we observe, makes no predictions. It’s only supposed explanatory value is useless, because it relies on circular definitions. (What is an intelligent agent? An agent that intervenes in ways that couldn’t be observed in nature. How do we know it’s intelligent? Because it intervenes in ways that couldn’t occur without intelligence. How do we know that it couldn’t occur without intelligent intervention? Because that’s how we defined it.)

  3. Tim G


    I hope you are managing reasonably well and your predicament improves more rapidly.
    We’d love to hear your account of the storm and its aftermath.

    Anyway, I had been wondering what statistical methods (if any) could be used to assign a probability to a particular storm being due to global warming. I thought that perhaps an argument could go something like this: If some model predicted that such a storm would have a 0.04% probability of occurring without global warming and a 0.07% chance that it would occur with the current conditions, then there would be a three in seven chance that the storm was due to global warming.

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  5. Tom

    There’s a fourth factor related to severity: global warming has caused sea levels around New York to rise about eight inches in the past hundred years, which means the peak flooding was eight inches higher than it would have been otherwise. This equates to about 48000 people seeing flooding who wouldn’t have. Additionally, damage from flooding is, according to the Army Corp of Engineers, exponential with height of floodwaters.

  6. bob

    Saying that “Increasing the amount of energy in the environment definitely has an effect on weather patterns” is incorrect:

    1 – You just can’t “increase the amount of energy”. Otherwise you violate the first and second laws of thermodynamics.
    2 – Weather patterns, as you suggest in your article, are attributable to temperature. Not energy. Actually I think you should have said temperature gradients, not just temperature.

    1. MarkCC Post author

      Amazing how many errors you’ve managed to pack in to a short comment.

      (1) Temperature *is* energy. The temperature of something is a measure of its aggregate kinetic energy.

      (2) Global warming is completely about energy. We receive energy from the sun. Some of that energy is absorbed by air, water, and land; some of it is reflected; some of it radiates away. Global warming is the result of a change in the atmosphere, which changes the amount of energy that we retain, versus the amount that we reflect/radiate away.

      (3) Increasing the amount of energy in the environment is in no way, shape, or form a problem for thermodynamics. It’s the result of a change in the absorption/radiation ratio.

      (4) Global warming isn’t about changing temperature gradients. It’s about changing *temperature*. The global average temperature is increasing. It’s not about change in gradients; it’s absolute change. We’re retaining more of the suns energy, radiating less energy, and that creates an increase in the amount of energy in the atmosphere.

      1. John Armstrong

        Well, strictly speaking temperature is the derivative of the internal energy of the system with respect to entropy, not energy itself. Almost certainly this increases along with energy for this system, but if you’re going to go pointing out errors…

    2. Kevin

      1) The energy came from the sun, and stayed in earth’s atmosphere due to pollution, and warmed the water. No thermodynamic laws violated.
      2) Temperature is energy. It’s thermal energy.

  7. Tim G

    When someone is accustomed to dealing with problems with vast quantities of parameters that can be reduced to far fewer independent parameters, he sees two quantities that are dependent as being essentially the same thing. For example, the radius, diameter, cross-sectional area, and perimeter of a cylinder are all essentially the same, because any one of those four is sufficient information to tell you the other three. Information regarding the other three would just be redundant.

    For a material of a particular composition, mass and phase, the temperature is sufficient information to derive its thermal energy. So, I think I understand why MarkCC would write that temperature *is* thermal energy when he obviously knows it is not literally so.

    BTW, if we want to be truly pedantic about definitions, we would limit the term “heat” for transferred thermal energy, but I suspect most physicists don’t bother with that.

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  10. Geosci

    The problem with your assessment of Sandy and global wamring, is you ignore precident. This is by no means the first large hurricane ever to strike this far north. 84 hurricanes (that we know about) have struck New York since the 17th century. For example: August 19, 1788 — A hurricane strikes New York City and is reported to have left the west side of the Battery “laid in ruins” after severe flooding occurs. Sound familiar? Anyway, the only viable method for you to prove your point would be to examine the frequency of hurricanes, and hurricane intensity, in a specific area over a long period of time. If the frequency was increasing, then perhaps you could seach for causation.

    On another point – Your theory is that water is warmer, warm water fuels hurricanes, ergo gobal warming creates more hurricanes takes several rather silly logical leaps. Is the warm water caused by global warming? No, it is not “by definition” global warming. It is a possible symptom of such. Does warmer water increase hurricane frequency (there are several well supported theories on how a warmer earth actually decreases frequency and intensity of storms, but I’ll let you hunt those up. Anyway, very sloppy logic, and a sloppy post. You could be right, but you present exactly zero evidence and weak logic to support your claim.

    1. MarkCC Post author

      Your criticism has quite a number of errors of its own.

      (1) I am not ignoring precedent. Hurricane Sandy was absolutely unprecedented in records.
      There have been hurricanes in the NY area in the past, and they’ve done damange, but
      Sandy was far larger, with a larger storm surge than any ever recorded.
      Go ahead and check: Sandy had the largest storm surge ever recorded in NYC.

      (2) We do know that warm water fuels hurricanes. Note the phrasing of that statement:
      warmer water doesn’t cause hurricanes. It fuels hurricanes.
      Again, this is something that has been extensively studied, and it’s used every
      year by weather forecasters tracking hurricanes. Hurricanes pick up energy and
      become stronger over warmer waters, and lose energy and weaken over colder waters and over

      Whether warmer waters *cause* more hurricanes is up for debate. The evidence that’s been
      analyzed so far suggests that it probably doesn’t, but it’s far from a decided question.
      But whether passing over warmer water adds energy to hurricanes? Not a question at all.

      (3) Global warming is nothing more and nothing less than the observed fact that average temperatures
      have risen. Ocean warming is exactly one of the phenomena that we measure to compute those average
      temperatures – so *by definition*, ocean warming *is* global warming. Ocean warming isn’t
      *the cause* of global warming – it’s a part of the observed phenomenon that global
      average temperatures are rising. That says nothing about the *cause* of global warming.
      All of the evidence points to the fact that the observed phenomenon
      of global warming is caused by human action. But the factor or factors that are causing global
      warming are not the same thing as the phenomenon – and even if it were to turn out that human
      action has nothing to do with temperature change, it wouldn’t change the fact that the average
      global temperatures – including ocean temperature – has risen.

      When it comes to hurricane sandy, there are two facts that are absolutely clear about it.

      The first is that it was much stronger than a typical hurricane that made it so far north.
      Hurricanes normally weaken as they move north. Sandy didn’t, and the weather models that predicted
      it so precisely were based on the well-understood phenomenon of warmer water strengthening the
      storm. This is not something that’s honestly debatable: it’s a simple fact that warmer water strengthen
      hurricanes, and that hurricane Sandy strengthened in the time it was over unusually warm water, and that that strengthening was a major factor in the severity of the storm when it came aground. On this point alone, it is undeniable that global warming was a factor in the severity of hurricane Sandy.

      The second major factor is the track that the storm followed. There are many Atlantic storms that follow the same path that Sandy started on. In general, they drift north-northeast and disappate as they lose energy in the colder latitudes. But as it came north, Sandy made a dramatic and highly unusual left turn.
      Why? Again, we know why: because of the negative NEO – an unusual weather pattern coming from the northeast. A pattern that we were able to predict well in advance, because we’ve got a pretty good idea of what caused it. It’s absolutely certain that the negative NEO caused the hurricanes left turn; the cause of the NEO is not as dead-certain as the warm water providing energy to the hurricane, but we can say that it’s highly likely that it was caused by ice-melt, which in turn was caused by warming.


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