/ Maggie Koerth-Baker / 10 am Mon, Oct 29 2012
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  • Did climate change cause Hurricane Sandy? The answer depends on why you're asking

    Did climate change cause Hurricane Sandy? The answer depends on why you're asking

    There are two answers here: One for the legitimately curious, and one for people who want a disaster to be a referendum on climate change.

    Image: Oct. 28, NASA/NOAA polar orbiting satellite. Detail above, full below.

    Last year, I wrote a piece for BoingBoing about destructive storm systems and why it's so difficult to say, in concise sound-bite form, what relationship that destruction has to climate change. In that case, we were talking about tornadoes. But over the last couple of days, lots of people have been having roughly the same conversations about Hurricane Sandy. When the clouds have passed and everybody is done sleeping in airports, people are going to want answers. Was this an unavoidable act of nature? Or was this something caused directly by changes to Earth's climate that have happened because we burn fossil fuels which increase the concentration of carbon dioxide in the atmosphere?

    Again, there's not an easy answer. And, again, part of the problem here is that we're expecting science to operate on the scale of American media news cycles, which doesn't really work. We want to talk about this while the storm is raging or, barring that, at least immediately afterwards. But scientists aren't really going to have anything particularly deep to say about this specific storm for months, if not years. During that time, data will be analyzed and compared, and other events will happen, and that's really the stuff that we need in order to say much of anything other than, "We don't know for certain." In some ways, expecting anything else means forcing scientists to speculate and extrapolate in ways they aren't usually comfortable with and that aren't a terribly great way to understand the big picture.

    But there's also something new, that I kind of didn't really think about when I was writing that post on the tornadoes. The answer to these questions also really depends on the motivations behind why you asked, and what it is that you really want to know.

    First off, you should know that this kind of extreme (and extremely weird) storm system happening in fall or winter is a trend that some scientists had already been predicting. Those predictions stem from the steep reduction in quantities of sea ice in the North Atlantic and what we know (and think we know) about how that change affects climate patterns and storm formation as a whole.

    Remember the times that we've talked about how climate change can, seemingly paradoxically, lead to heavier snowfall in winter? This is connected to that. Here's how Kate Spinner with The Herald Tribune explained it:

    A big bubble of high pressure, with sinking air that moves clockwise, is interrupting the typical steering patterns in the atmosphere. That high pressure creates a blockage, backing up the jet stream so that it bends south, eventually looping north again, instead of flowing toward the east as usual.

    The blocking pattern, centered just south of Greenland, will significantly slow the eastward-moving cold front once it reaches the coast. And it will steer Sandy into the U.S. rather than allowing it to turn east.

    Blocking events are the force behind a lot of crazy weather anomalies, not just hurricanes. And there's evidence suggesting that, as the ice in the Arctic melts, the frequency and/or intensity of the blocking events may be increasing. The Climate Crocks blog did a nice interview about this a few months ago with Jennifer Francis, who studies marine and coastal sciences at Rutgers.

    There's more on this from Francis, and other scientists, at Andy Revkin's DotEarth blog.

    Another thing worth taking into account: Weather is a lot more complicated than you think it is. If it rains today — or if it doesn't rain — there are lots of different, interacting factors that influenced that outcome. A good way to think about it is like a plane crash. It is very, very rare for a plane crash to be caused by a single mistake. Instead, when you're reading the final report, you find that lots of things have to go wrong all at the same time. Even then, you still might not get an accident if the mix of mistakes that happen don't interact with each other in such a way as to make them all worse than the sum of their parts.

    Plane crashes are complicated. And so is weather. That matters, because it means that Hurricane Sandy could be both a completely natural occurrence and a product of climate change. Simultaneously. Some of the factors that caused this storm might be nature-made. Others might be man-made. And teasing apart which factors were responsible for which aspect of the storm's damage is incredibly hard.

    Greg Laden, an anthropologist who does some very good blogging on climate science, had a lot to say on this topic — particularly, the fact that even though we can't say "Hurricane Sandy was caused solely by climate change", we can say that climate change is probably affecting several factors that probably influence the development, growth, and movement of hurricanes.

    It is often said that storms are going to happen anyway, but global warming ramps up the probability, which is akin to saying that there is always going to be variation in temperature or some other weather related factor but global warming raises the baseline. That’s true. But the corollary to that is NOT that you can’t link climate change to a given storm. All storms are weather, all weather is the immediate manifestation of climate, climate change is about climate. Before we started talking about global warming, storms were caused by … things. Climate things. Did we ever say, back in the 1950s when a hurricane hit Florida, “Oh, ya, that was some hurricane, but the thing is, you can’t really attribute a given hurricane to the Intertropical Convergence Zone’s relationship to warm Mid Atlantic currents. The former is a weather event and the latter is a climate system.” Why did we not ever say that? Because it would have been irrelevant, even dumb.

    The truth is, we experience more Atlantic severe storms because of global warming, though we are still working out the details of which features of which kinds of storms are affected most. Beyond this, it may well also be possible that something I hinted at above is true: We may be experiencing kinds of storms today that were very rare in recent centuries, because of global warming.

    Adam Frank at NPR also wrote a good post on this subject. In it, he explains another issue that muddies the waters. When we say that weather is complicated and that a storm is caused by the interaction of lots of different factors, what we are really saying is that weather is a system. Just like climate is a system. Currently, there are some systems that science understands better than others. Hurricanes are, unfortunately, pretty far down on the list.

    There is a hierarchy of weather events which scientists feel they understand well enough for establishing climate change links. Global temperature rises and extreme heat rank high on that list, but Hurricanes rank low. As the IPCC special report on extreme events put it "There is low confidence in any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity (i.e., intensity, frequency, duration), after accounting for past changes in observing capabilities."

    The reasons for "low confidence" are manifold. Some part of the caution comes from the complexity of the problem, and some part comes from the lack of good data before the satellite era (about 1970). Thus, many climate scientists will not want to go out on a limb for hurricanes. They just don't have the tools to make strong inferences.

    This is not to say progress isn't being made. One thing that does seem clear is that warmer oceans (a la global warming) mean more evaporation, and that likely leads to storms with more and more dangerous rainfall of the kind we saw with Hurricane Irene last year. In addition, a paper published just last month, used records of storm surges going back to 1923 as a measure of hurricane activity. A strong correlation between warm years and strong hurricanes was seen. Thus if you warm the planet, you can expect more dangerous storms.

    Basically, we know that the effects of climate change probably has an impact on factors that cause massively destructive storms — even if we don't know exactly how much of an impact; even if we can't really use that information to exactly predict what's going to happen with massive storms in the future; and even if we can't tell you whether Sandy, specifically, was caused by climate change.

    So, really, the answer to the question, "What is the relationship between Hurricane Sandy and climate change", depends primarily on why you're asking the question.

    If you're just kind of curious and/or looking for something to blame, we don't have great answers on that yet. I'm sorry. Nobody is really going to be able to tell you one way or the other.

    But if you're using that question as a proxy to really ask, "Is climate change real and do I have to care about it?", well, good news! We have enough information to answer your question. And the answer is, emphatically, yes.

    Read More:
    Besides the links I included in the story, I want to point you towards a couple more Hurricane Sandy-related things:
    NOAA's Storm Central has all the maps, satellite images, and projections of Sandy that a concerned citizen (or giant nerd) could want
    • The director of the National Center for Disaster Preparedness would like you to know that we are seriously, seriously NOT prepared for big disasters
    Atlantic City is totally flooded
    • Marketplace Tech Report has a really fascinating piece on the future of weather forecasting
    • If you're in Sandy's path and aren't really clear what to do with your pets, read this
    • The NASA Satellite video will haunt your nightmares
    • Meanwhile, the news that the satellites we rely on for forecasts of hurricanes are aging rapidly (and there aren't great plans to replace them) will create your nightmares
    Use this handy slider to compare Hurricane Irene and Hurricane Sandy

    Special thanks to the following people: Bryan Walsh, Ed Yong, CBS Smart Planet, Andrew Thaler, Katherine Hayhoe, James Greyson, Lisa Fleisher, John Matson, and Jennifer Viegas.

    / / COMMENTS

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    1. Once again, I find myself going through the same steps:
      1. See an interesting looking science headline from Boing Boing
      2. Read partway through, and stop, thinking “this article is especially informative, but also easy to understand”
      3. Think “this must be an article by Maggie”
      4. Scroll up and see the byline to confirm my intuition

      Great job, as always!

    2. Nice piece. I do want to note that ‘Climate Change’ is a term politicos came up with when they don’t want to confront the science. It’s more marketing ploy than anything else. It’s what politicians say instead of ‘Global Warming’ when they don’t want to scare anyone.

      1. At the same time I think that ‘Climate Change’ is more relatable.  Ultimately what most people are witnessing are extreme weather conditions and seasons becoming a little fruity.

        Here in the UK for example using terms like ‘Global Warming’ may bread skeptics, as even if average temperatures are increasing what’s notable is how shit our summers have been recently.  Our weather is also temperate enough that it’s not that rare for someone to seem quite excited about the impending warming of the globe.

        1. Somehow I don’t think it would be helpful to tell such people that melting ice could shut down the gulf stream and make the UK colder…

        2. But in actual point of data and evidence the global trend is towards warming, not cooling. I agree that its imperfect, but shouldn’t the term at least reflect the GHG heat trapping element? So, on balance, I agree, Climate Change is too much corporate focusgroupspeak

          1. I wasn’t contending that the global temperature was rising, in fact that’s a major aspect of my entire point.

            I’m happy to use whatever term makes people listen, and it doesn’t surprise me that the terminology is more effective if people can relate to it. It’s a factually accurate description anyway – in fact you could argue that it’s more nuanced – so I don’t see it doing any harm.

            tl;dr: Whatever works.

      2. Climate change and especially the term global abrupt climate change is a much more accurate representation of the phenomenon than is global warming. Global warming via the greenhouse effect may be the primary cause of the climate change but it is certainly not the whole picture.

      3. David, I’ve heard that rhetoric, but I respectfully disagree with it. I think “global warming” misleads people about what to expect. Climate change is a hell of a lot more accurate, when it comes to the range of effects that people experience on the ground. 

        I’d use “global weirding”, but I think it’s a bit too precious. 

    3. I think, somewhere down the road, if we can reasonably approximate the percentage of storms that were caused by anthropogenic climate change, we should start naming that proportion of storms after individuals (politcians, energy tycoons, unethical industry scientists)  who were cultural leaders in the denial movement.   

        1. I know it’s petty and not really productive.  But as one of those in the path of the storm, I feel entitled to a bit of a giggle. 

            1. Well, if the damage is already done then I don’t see the harm in saying “I told you so.”  Hollow victory is better than none at all, right?

    4. “One thing that does seem clear is that warmer oceans (a la global warming) mean more evaporation”.

      That doesn’t seem clear to me.  Is he saying there will be higher humidity, more moisture transport, or what?  I get that higher atmospheric temperature will increase airborne moisture by about 4%, but the relative humidity of the system will be about the same.

      1. Hot air heats up water, no?  Is the water in puddles warm on a hot day, or cold?  When the heated air covers a huge area of any part of the globe, the oceans heat up!  When they do, the water evaporates!  The excessive water in the air causes turbulence, i.e., storms!  When the pot boils, is the water roiling???  It is in my pot!  The ocean temps in hurricanes is over 80 degrees!  There are huge swaths of the world’s oceans now that are ALWAYS warm!  That’s what global warming does, under pressure of the cap greenhouse gases creates above, keeping hot air compressed, and the oceans hotter!

        To simulate, put a lid on your boiling pot of water!  THAT’S the greenhouse gases stopping up the heat!  Note how it boils more and more violently!  It tries to push the lid off!  THAT’S whatchacall the storms at present, and the storms to come!  

        Global warming is EASY TO GET once your head isn’t stopped up with lies, from dupes and dirty energy profiteers, claiming it doesn’t exist!!!!!

        Enjoy the storms, and get used to them!  They’ll be growing in strength every year until the greenhouse gases we’ve filled the atmosphere with dissipates in a century!  Of course, LONG before then the methane that is being released now, and which is 20 times more powerful than CO2, might kill us all first!

        Thanks for being so stupid!   

        1.  And thanks for coming off as a condescending jerk.  KWillets question, as I read it, doesn’t appear to be written by a stupid person.  I recognize that emotions are running high, especially with a huge election around the corner and a once-a-(insert insanely long figure here) storm battering the Eastern Seaboard, but your soapbox science rant seems a touch exclamation-pointy, a little nutty, and downright rude at the end.How ’bout we tone it down a touch, Sparky?  Certainly we can have a civilized discourse about such topics? 

      2. Well, I guess I should know better than to ask a science question on Boingboing, but I did manage to find a research paper that covers the same points:
        Muted precipitation increase in global warming simulations: A surface evaporation perspective

        The abstract covers my concerns almost exactly:

        A 90-year analysis of surface evaporation based on a standard bulk formula reveals that the following atmospheric changes act to slow down the increase in surface evaporation over ice-free oceans: surface relative humidity increases by 1.0%, surface stability, as measured by air-sea temperature difference, increases by 0.2 K, and surface wind speed decreases by 0.02 m/s. As a result of these changes, surface evaporation increases by only 2% per Kelvin of surface warming, rather than the 7%/K rate simulated for atmospheric moisture.

        This is another concern I thought of, which they luckily cover as well:

        owing to its thermal inertia, the ocean lags behind the atmospheric warming, and this retarding effect causes an increase in surface stability and relative humidity,

        That’s essentially what wasn’t clear — relative humidity (actually the difference between RH and 100%) largely determines the evaporation rate, and RH decreases as temperature increases, unless more water is added, which is what is expected to happen, so nothing is clear at all.

        1. Well, I guess I should know better than to ask a science question on Boingboing,

          Usually the comments are better than this and the only problem you’d have is that someone would link you to lmgtfy for asking an easily googled question. BB commenters are pretty smart and with-it for the most part.

        2.  Also, everything else being equal, more heat means more evaporation — and that is kinda common sense.

          Yes, yes, relative humidity.  But increased heat increases the capacity for air to hold water and increases the rate of evaporation.  So while you can probably come up with some convoluted reason why increased temperatures wouldn’t result in more evaporation it would need to be really convoluted.

          1. You seem to be confusing “heat” as temperature vs. energy transfer.  The amount of heat energy entering the system is the same, unless you buy the hotter-sun idea, and some of this energy goes into evaporating water, but it’s not clear why more energy would go into that process.  It’s a Carnot cycle.

            Any temperature can have 100% RH, with a net evaporation rate of zero.  It’s not convoluted at all.  

            1. I don’t think I’m actually confused about this but your argument isn’t actually making sense to me.

              Total energy under greenhouse effect goes up.  The amount entering the system stays the same but less is radiated into space so the total increases.  This increase in total energy is absolutely relevant to the rate of evaporation:
              1) It increases the capacity of air to contain water vapor.
              2) It increases the rate of evaporation of water — regardless of relative humidity.  If relative humidity is high then condensation and evaporation may happen at the same rate, but because of (1) we’re essentially guaranteed this isn’t the case.  There will be some increase in evaporation even if feedback suppresses it somewhat.

              Any temperature can have 100% RH, with a net evaporation rate of zero.  It’s not convoluted at all. 

              But is this a realistic real-world scenario?  100% RH everywhere all the time?  I think to make your argument that evaporation wouldn’t increase at all — to argue that there is 100% RH everywhere all the time, essentially, would actually require an incredibly convoluted argument.

            2.  And actually, 100% relative humidity everywhere all the time would still imply more evaporation given an increase in atmospheric temperature.  The increase in temperature requires that “100% RH” means a larger partial pressure of water vapor in the atmosphere than under the cooler temperature.  To maintain 100% RH under higher temperatures requires more water vapor — and that’s going to come from evaporation.

              You’ve convinced me it isn’t common sense, though, since my argument is based on general scientific knowledge that a lot of people don’t spend a lot of time learning or thinking about.

    5. Sure, pals. So you want to jump through barbed hooks to be able to state that “maybe, you know, it’s not entirely global warming’s fault”. And I accept that.But – please – stop being stupid. Of course global warming has lots to do with this. Of course global warming is caused by human intervention, overindustrialization and lack of actual effort into moving to noncombustive power. And of course we’re all gonna die sweating and drowning unless things change soon. Very soon.

      End of story.

      1. Assuming AGW gets as bad as it looks like it will…

        not everyone will die.  Those that do will mostly die of starvation or thirst or be killed as a result of looting or warfare.  But yeah, generally agree with you otherwise.

    6. Meh, why do we have to try and frame it in absolutes? Yes there is a natural cycle, but the magnitudes involved are likely influenced by modern human activity.

    7. Isn’t mother nature grand?  She is simply obeying the Laws of Physics. ‘Man’ and ‘his’ inability to understand the rules and work in line with them has caused these ever increasing occurances.  Maybe ‘man’ will get the hint now?  When you work in a system governed by laws, you are not above them.  Burn gases here, build highrise there, act without understanding larger consequences etc,- you will change weather patterns.  And the root cause of man doing all of this is greed – putting self above the rest and thinking only of ‘his’ sort term pleasure at the expense of the rest.  I find it interesting that mother nature aka laws of physics pushes back and, through its actions causes us to wake up – maybe just for a moment – look outside of ourselves and our comfort zones, and gather together to help one another.  Those you ignored yesterday, suddenly you rely upon. I’m starting to see a pattern here. 
      1. ignore rules of nature, and be interested in only ‘self’,
      2.  laws of physics create balance within system by devastating communities
      3.  people forced to come together and help each other.
      4.  go back to greedy self servings ways.
      Insanity: doing the same thing over and over again and expecting different results.
      Albert Einstein
      Hmm, makes you think we’re all lunatics, doesnt it?  Maybe we can start to leave out #4 now?

      1. Very good points! I often wonder why we humans persist in going outside ourselves to latch onto some self satisfying answer. It only leads to a kind of masochism and since we are all connected in this denial it’s actually a kind of sadism. Never find the solution closest to you for fear that you can’t face your own complicit cooperation in the massive imbalance that we have created….together!  Logically, even if we can’t understand consequences of our actions upon the climate, and how our inhumanity multiplies, the world would be a much better place for humans if we practiced mutual responsibility and progressed to a state of unified humane values.

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