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How Global Warming Made Hurricane Sandy Worse

As officials begin the arduous task of pumping corrosive seawater out of New York City’s subway system and try to restore power to lower Manhattan, and residents of the New Jersey Shore begin to take stock of the destruction, experts and political leaders are asking what Hurricane Sandy had to do with climate change. After all, the storm struck a region that has been hit hard by several rare extreme weather events in recent years, from Hurricane Irene to “Snowtober.”

Photo of coastal flooding in Mantoloking, New Jersey, taken from a New Jersey Air National Guard Helicopter.
Credit: NJNG/Scott Anema.

Scientists cannot yet answer the specific question of whether climate change made Hurricane Sandy more likely to occur, since such studies, known as detection and attribution research, take many months to complete. What is already clear, however, is that climate change very likely made Sandy’s impacts worse than they otherwise would have been.

There are three different ways climate change might have influenced Sandy: through the effects of sea level rise; through abnormally warm sea surface temperatures; and possibly through an unusual weather pattern that some scientists think bore the fingerprint of rapidly disappearing Arctic sea ice.

If this were a criminal case, detectives would be treating global warming as a likely accomplice in the crime.

Warmer, Higher Seas

Water temperatures off the East Coast were unusually warm this summer — so much so that New England fisheries officials observed significant shifts northward in cold water fish such as cod. Sea surface temperatures off the Carolinas and Mid-Atlantic remained warm into the fall, offering an ideal energy source for Hurricane Sandy as it moved northward from the Caribbean. Typically, hurricanes cannot survive so far north during late October, since they require waters in the mid-to-upper 80s Fahrenheit to thrive.

Scientists said about 1°F out of the 5°F East Coast water temperature anomaly may have been due to manmade global warming. Warmer seas provide more water vapor for storms to tap into; that water vapor can later be wrung out as heavy rainfall, resulting in flooding.

The most damaging aspect of the storm was the massive storm surge that struck the coastline from Massachusetts to Maryland. Global warming-related sea level rise gave the surge a higher launching pad than it would have had a century ago, making it more damaging than it otherwise would have been. This is only going to get worse as sea level rise continues as a result of warming ocean waters and melting polar ice caps and glaciers.

The storm surge at The Battery in Lower Manhattan was the highest ever recorded at that location. It surpassed even the most pessimistic forecasts, with the maximum water level reaching 13.88 feet above the average of the daily lowest low tide of the month, known as Mean Lower Low Water, including a storm surge component of 9.23 feet. That broke the official record of 10.5 feet above Mean Lower Low Water set in 1960 during Hurricane Donna, as well as a record set during a hurricane in 1821.

A water vapor satellite image of Superstorm Sandy on Tuesday, Oct. 30.
Click to enlarge the image. Credit: Stu Ostro/Facebook.

Or, to put it in simpler terms, the water level reached 9.15 feet above the average high-tide line.

Katharine Hayhoe, a climate researcher at Texas Tech University in Lubbock, said manmade climate change likely contributed to the storm surge at The Battery in Lower Manhattan, with 15 inches of long-term sea level rise recorded at that location, the result of manmade sea level rise, sinking land, and ocean currents. She said the manmade contribution to the storm surge may have been a small amount.

But to the Metropolitan Transit Authority or Con Ed, the main electric utility in Manhattan, each inch of sea level rise matters a great deal.

If a similar storm were to strike New York in 2050, it would cause even more damage, since sea levels are expected to be considerably higher by midcentury. In fact, a recent study found that sea level rise has taken place at an accelerated rate at locations north of Norfolk, Va., and if this pace continues the Northeast could see much higher sea levels than other parts of the East Coast by midcentury.

A 2012 report by the U.N. Intergovernmental Panel on Climate Change (IPCC) found that sea level rise has likely increased extreme coastal high water events around the world.

By warming the seas and the atmosphere, global warming is also expected to alter hurricane frequency and strength, making North Atlantic hurricanes slightly more powerful, while reducing the overall number of storms during coming decades. Detecting such changes in the observational record is difficult, considering the varying ways people have kept tabs on hurricanes prior to the era of hurricane hunter aircraft flights and satellite imagery. A recent study published in the Proceedings of the National Academy of Sciences found that warmer sea surface temperatures are tied to an increase in stronger Atlantic hurricanes.

“Blocked” Weather Pattern

In addition, an unusual weather pattern in the northern hemisphere steered the storm in an unprecedented direction, as it made a dramatic — and for many East Coast residents, catastrophic — left hook right into coastal New Jersey. The east-to-west movement, which is exactly the opposite of how weather systems normally move in this area, helped maximize the storm surge, since a strong easterly air flow struck the coast at a right angle.

Satellite loop from the University of Wisconsin, showing Hurricane Sandy as it made landfall in New Jersey.

The upper-air flow over the Atlantic Ocean was temporarily jammed by a powerful area of high pressure near Greenland and a storm system in the Central Atlantic, leaving the storm no escape route away from the U.S. Such patterns are known as “blocking” events, and they have occurred with increasing regularity and intensity in recent years. Blocking patterns have been linked to several noteworthy extreme weather events, such as the deadly 2010 Russian heat wave and Pakistan floods, the 2003 European heat wave, and the March heat wave of 2012 in the U.S.

In this case, the blocking pattern, occurred at precisely the wrong time — when a hurricane was moving out of the Caribbean.

Weather Channel hurricane expert Bryan Norcross wrote about this on Oct. 26. “The freak part is that a hurricane happens to be in the right place in the world to get sucked into this doubled-back channel of air and pulled inland from the coast,” he said. “And the double-freak part is that the upper-level wind, instead of weakening the storm and simply absorbing the moisture — which would be annoying enough — is merging with the tropical system to create a monstrous hybrid vortex. A combination of a hurricane and a nor’easter.”

Some, though not all, scientists think the more frequent blocking events may be related to the loss of Arctic sea ice, which is one of the most visible consequences of manmade global warming. The 2012 sea ice melt season, which ended one month ago, was extreme, with sea ice extent, volume, and other measures all hitting record lows. The loss of sea ice opens large expanses of open water, which then absorbs more of the incoming solar energy and adds heat and moisture to the atmosphere, thereby helping to alter weather patterns. Exactly how sub-Arctic weather patterns are changing as a result, however, is a subject of active research.

Some researchers who warn that climate change is already being felt in extreme weather events, such as Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colo., are not yet convinced of the Arctic connection. Others, such as Hayhoe, think it is a “plausible theory” that is worth investigating, although she noted there is evidence that Arctic warming may cause more blocking during the winter rather than during the fall.

James Overland, a scientist with the National Oceanic and Atmospheric Administration who recently published a study on how Arctic sea ice loss is altering the weather in the Far North, said it’s not clear whether Hurricane Sandy was just a freak event or a sign of things to come. “What was highly unusual to me was the slowing down of the jet stream that normally turns hurricanes out to sea, allowing Sandy to directly [make] landfall,” he said in an email conversation. Yet, he said it’s important to recognize that there is still a huge role played by randomness, or chaos, in global weather patterns. “Having looked at a lot of weather maps, I don’t think it’s entirely legitimate to make a big possibility for an Arctic connection with Sandy rather than the chaos default,” he said.

And while climate change has undoubtedly altered the background conditions in which all weather systems are born, scientists said that natural variability still plays a very large role, and may have been the dominant factor with Hurricane Sandy.

Martin Hoerling, a researcher at the Earth Systems Research Laboratory, also in Boulder, is a proponent of this view. “Great events, like this meteorological one, can happen with little cause(s). Individually, neither the tropical storm nor the extratropical storm that embraced it, were unusual,” he said via email. “What makes this a rare, perhaps once-in-a-lifetime event, is the fortuity of their timely (“untimely” as far as most are concerned who sit in harms way) intersection.” Randall M. Dole, who is a colleague of Hoerling's at ESRL, noted that the blocking pattern that helped steer Sandy was "highly transient," which suggests to him that it was just "random bad luck" that it coincided with a hurricane along the East Coast.

Regardless of the chain of events that led to this disaster, Hurricane Sandy is almost certain to wind up being one of the top 10 costliest hurricanes on record, and it comes soon after Munich Re, a global insurance giant, warned of increasing natural disaster losses in the U.S., a trend the company said is related to global climate change.

And regardless of links between this particular storm and manmade climate change, Hurricane Sandy revealed many pressing questions. Like how much climate change is affecting storm impacts and extreme weather trends, and how vulnerable our coastal populations and infrastructure are to the those changing risks. These are questions that political leaders, scientists, and engineers will be grappling with for many decades to come.

Related Content 
Hurricane Sandy Paralyzes New York, New Jersey
Hurricane Sandy Walloping East Coast With Surge, Winds 
Hurricane Sandy Roars Ashore, Threatening Record Surge 
Sandy's Storm Surge Explained and Why It Matters
Ongoing Coverage of Historic Hurricane Sandy
Hurricane Sandy Set to Deliver Massive Blow to East Coast
Hurricane Sandy’s Five-Fold Flood Threat, with Local Maps 
How Fujiwara Effect Will Toss Sandy Into U.S. 
Officials Warn of Hurricane Sandy's Rare Damage Potential 
How Hurricane Sandy Can Become a 'Frankenstorm'
Sea Level Rising Faster Than Average in Northeast U.S. 
New York's 1-Inch Escape From Hurricane Irene 

Helpful links for following the storm:
National Weather Service Storm Central 
Climate Central Surging Seas Mapping Tool
New York Times Live Blog
Capital Weather Gang blog
Google Hurricane Sandy Crisis Map


Twitter Accounts to Follow:


By UncleanHands
on October 31st, 2012

There should be no insurance money for extreme weather losses to those who fund the campaign to sow doubt about climate science.  We do not let arsonists recover insurance after they torch their own house and murders can not inherit from their victims even if they are named in their victims wills.  Same difference.  This is even more true when we talk about taxpayer dollars being handed out from govt relief agencies.

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By cavetrollhead
on October 31st, 2012

The title made me chuckle.  This paragraph made me chuckle more and “What is already clear, however, is that climate change very likely made Sandy’s impacts worse”  Uncleanhands comment made me sick.  Loonies from the left. .. .

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By Steve Bloom
on October 31st, 2012

Still not cutting it, Andrew.  Months from now those D+A studies will find a fractional AGW component, but that sort of thing has been shown to be nearly useless in terms of public impact.  Three things you (and other journos, and scientists) need to face up to are:

1) Even in a situation where we are being hit with a rapid-fire series of AGW-fueled events (hmm, maybe a little like the present, yes?), formal D+A won’t be able to do much better than we see at present.

2) An inherent property of our imperfect understanding of climate in a time of rapid climate change is that scientists who refuse to draw other than formalistic conclusions are necessarily far behind the curve of the change, and journos like you who insist on following them in turn are even worse off.  A corollary is that we will start to see the public and politicians getting out in front, as with Cuomo’s remarks today.

3) Even where AGW has been determined to be responsible for e.g. just 20% of an event, it has disproportionate responsibility for the damage (and note that this reasoning applies to things like the unusual NW Atlantic heat that allowed Sandy to survive so far north).

Try to imagine how you can do better.

BTW, via Stefan Rahmstorf it would seem that the persistent Greenland high consequent to sea ice loss was predicted (see figure 3h).

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By Andrew Freedman (Brooklyn, NY)
on October 31st, 2012


What would an ideal news story or analysis of this event and its relationship with global warming look like, in your view?


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By Rob (Buffalo, NY)
on October 31st, 2012

You’re really going to dismiss the 1821 hurricane like that?  It made landfall EAST of Manhattan, yet flooded more of Manhattan, and did so at low tide.  Its by no means clear that Sandy broke that record.  Sandy was Cat 1, 1821 was probably Cat 3.

All well before the 1 degree temperature rise to which you attribute every recent calamity.  If its happened before, it can happen again, global warming or not.

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By Steve Bloom
on October 31st, 2012

Well, Andrew, I did identify three important elements, but it wasn’t intended as a comprehensive attempt at a restatement.  Tell you what, I’ll see if I can get P3 to host a group-sourced compare/contrast using this article and a few others.  It seems like a potentially very useful exercise.  Failing that I’ll write something myself.  Either way it won’t happen instantly, but soon.

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By Robert Marston (20877)
on November 1st, 2012

The tempo and intensity of extreme weather events will continue to increase from here. We will, likely see an event as bad or worse than Sandy on the East Coast within the next twenty years. The overwhelming player in the intensity and frequency of these events is climate change. And the climate that created the conditions for this fierce storm is getting worse.

Scientists don’t have much time to muck around with theory, at this point. The atmospher is changing faster than the science. Extreme events for just the US in 2012: 55 year drought, freak derecho, record fires, and the largest cyclone ever to strike the East Coast (what people are calling a 300 year event). Odds are the next year will be as bad or worse. Any fool can see climate change is causing it. Taking events completely out of context misses the, well, CONTEXT.

We’re not living in the 1950s anymore and their weather is not our weather. We’ve changed the conditions for the weather. And so to claim that any new, unprecedented event is not a product of those changes is utter blindness.

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By dan in illinois
on November 1st, 2012


Now those of us who have the temerity to question the theory of AGW are being thrown in with murderers and arsonists?  You’re really tough on us.

By the way, didn’t I see you at the Occupy Wall Street demonstrations last year?

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By Lewis Cleverdon
on November 1st, 2012

Andrew - Steve has a point here that attribution studies are effectively a deferral and minimization of cultural impact, not least by treating each event in isolation, when understanding our position demands the synthesis of the long series of increasingly extreme events.

What can be said with confidence, as an opinion if not an IPCC-accredited statement, is that Sandy would not have retained power without the anomalous SST, and that it would neither have grown nor made landfall without the blocking high and Jetstream disruption. - No landfall, no damages.

Since the only cogent explanation of the Jetstream disruption is the loss of ASI, and the only cogent explanation of ASI loss is AGW, attribution studies seem worthy, but actually gratuitous compared to ongoing research in these fields.

What needs saying is that if, as expected, Jetstream disruption worsens with the trend of ASI loss, then any hurricane of any strength heading north from Florida, is liable to be steered slap into America’s east coast. Year after year.

While this prospect will have no influence on denialists, those they’ve duped and those who just can’t conceive of humans having such influence (who should be distinguished with the neutral title “flukers”) are another matter. As exceptionally extreme events are becoming commonplace the idea of them all being “just flukes” looks ever more ridiculous; with the warning now of Sandy’s successors potentially being annual visitors due to ASI loss, a major shift in flukers’ opinions becomes probable.

So please, step back from trying to limit articles’ conclusions to what is accredited by IPCC - your informed opinion is valid in its own right and needs to be heard - the scolds’ attempts to impose self-censorship is merely their appeasement of the right, and should be roundly condemned and then ignored.



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By UncleanHands
on November 1st, 2012

@Dan in Illinois;  Read my post again please.  I did not point fingers at EVERY questioner but at a specific subset. 

(1) Those who question via honest skepticism using the scientific method and reported in the professional lit are part of the solution. 

(2) Folks that accept TalkRadio drivel with little science education are too foolish to bother with;

(3) >>>>> BUT….. Strategists that finance the campaign to make the public doubt the honest science…... they are paying others to repeat oft-debunked lies.  Freedom of speech stops short of allowing people to falsely yell “Fire!” in crowded theaters.  It is just as bad to falsely tell guests in a burning hotel “There is no fire on the lower floors; just go back to bed”  And so those who finance the spread of oft-debunked falsehoods to create public doubt about global warming science should not receive either private insurance or govt relief dollars when they suffer losses from extreme weather made worse by their financing of that campaign.


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By Lisette Ehrat (Shobonier, IL 62885)
on November 2nd, 2012

I would appreciate a little help.  I heard Harry Smith on the Today show this morning.  He mentioned a 5 degree increase over normal in water temperature in the western Atlantic for the end of October. I see a similar statement (1-5 degrees, possibly man-made) in this article.  I looked up the NOAA stats, comparing the current western Atlantic water temperatures (Nov 1, 2012) to historical averages for the end of Ocober.  I’m am not seeing such a change as is being claimed, even further south.  What am I missing?


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By Andrew Freedman (Brooklyn, NY)
on November 2nd, 2012

@Lisette - Here is one global map of SST anomalies in late October, you can see the warmth off the East Coast. I saw much more regionally-specific data but can’t seem to find the URL at the moment. The data I saw also indicated significant SST anomalies in this region.

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By Lisette Ehrat (Shobonier, IL)
on November 3rd, 2012

Andrew - Thank you!  I appreciate the global view. Considering the locations and degrees of anomalies,  I’m still not seeing info to support Harry’s 5-degree-warmer-in-western-Atlantic-end-of-October claim.  I can understand how warmer water contributes more energy to hurricanes but I would expect to see warmer water somewhere along the track of this hurricane. If you find something, I would appreciate seeing it.
Thanks again.  I really do appreciate your help.  Lisette

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By Gail (Oldwick, NJ)
on November 4th, 2012

It seems obvious that the sea-level rise and the size of the storm are related to the energy humans are adding to the system by burning fuel and releasing millions of tons of greenhouse (heat-trapping) gases into the atmosphere. That’s high school science and as obvious as plate tectonics. Remember when that was a controversy? Or that seat belts in cars, or helmets for bikes save lives? Asking if climate change has something to do with Sandy is like asking if smoking has something to do with lung cancer. Remember when people could say with a straight face that it didn’t?

Having said that, there is a very large story that isn’t being reported which has little to do with climate change although it derives from the same processes.”¨”¨What is being ignored in this storm (and Irene as well) is the real source of the massive power outages that are so disruptive - which is all the trees that are falling on the lines. Trees didn’t used to fall with regularity on power lines - or people, cars and houses. The winds in both those storms were not extraordinary, nothing that a healthy tree shouldn’t be able to withstand.

Why are they falling now? ”¨”¨The answer is pretty obvious if you trouble to actually LOOK at them. They are all dying. Every species, every age, every location. They have obvious symptoms - broken branches, cankers, splitting bark, holes, thin crowns, early leaf drop, lack of autumn color, yellowing needles, bark covered with lichens and fungus. You can’t find a healthy tree anymore.

So the question becomes, why are they dying? Most foresters and scientists will say, climate change and/or invasive pests. But those explanations don’t fit the empirical evidence which is that even native pests and diseases have run amuck, and even young trees grown and watered and fertilized in nurseries exhibit the identical symptoms of decline. Even annual, tropical ornamentals in enriched soil in pots that like heat, and aquatic plants in ponds have injured foliage and stunted growth.

What do all of these plants have in common?  ”¨”¨The answer is, the composition of the atmosphere. Most people don’t realize it, because it’s invisible, but the background level of tropospheric ozone is inexorably increasing. Precursors from Asia travel across oceans and continents, and the persistent concentration has reached a threshold that is intolerable to the plants that absorb it when they photosynthesize. Agricultural yield and quality are reduced, and especially trees that are exposed to cumulative damage season after season are universally - around the world - in decline.”¨”¨This process has been well known to foresters and agronomists for decades, and demonstrated in field observations and controlled fumigation experiments. They just don’t want to publicize it, or even admit it, because the source is the emissions from industrial civilization itself. They would rather point to drought, insects, fungus and disease EVEN THOUGH it is well known that ozone debilitates plants causing their root systems to shrink as they allocate more energy to repairing damaged foliage, rendering them more vulnerable to drought and wind…AND impinges on their natural immunity to attacks from insects, disease and fungus, which exist precisely to break down dying trees, not destroy healthy trees.

Most of the trees that fell during Sandy were rotted inside.  New Jersey looks like the ecopocalypse has arrived.  Photos here:

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By Philip McAiney (Windsor, ON N9A 2R5)
on November 4th, 2012

Interesting how all the psychics in Indonesia, Haiti and Japan and now New York/New Jersey could not foresee the devastation of Sandy. Makes you think they are all frauds. The only person who knew of this disaster beforehand is the same one who knew of catastrophes months, years, decades, centuries and millennia in advance, and who had his predictions written-down for others could read. But because he said his predictions came partly from his long-time extraterrestrial sources, he was dismissed as a sicko-o and outright crank. Now we are finding out he was right all along. The individuals along the East Coast of the USA do not deserve the arrogance and high-handed conceit of their Governments and scientists that always claim they knew about these environmental shocks in advance.
The name of the man who foresaw these global terrorist acts of nature is Called Billy Meier who lives now as a 75-year old man in Switzerland. He is still having his contacts with his outer space friends as impossible as this might sound, and still writing them down so that others on Earth may one day read about them. Some of the writings are available now in English. Look under if you are interested. I hope you are one of the ones that is and can be a real helper to those that are now and will be helpless.

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By Bill (Grapevine, TX)
on November 5th, 2012

@unclean hands
It’s now clear why some people like to call you guys “eco-Nazi’s”. 

Please explain how global warming caused the 1821, and why 2012 is differnt from 1821.   

No one disputes that warming is occurring.  However, many of us don’t believe that the “scientists” have it all figured out regarding how much CO2 reduction will have any effect on anything, whether warming is actually “man-made”.  It’s funny how people who make a living off of climate science get really selective about which facts to base their conclusions on.  There is also no policing of the science community after it was proven via leaked emails that the “science” was being cooked.  Oh yeah,  there’s lots of skepticism and it is based on the science about scientists manipulating the facts to line their own pockets while the EPA goes after businesses and kills the jobs of non-scientists while millions are already out of work. 

You want to penalize people who fund opposition to climate science.  How about this . . climate scientists have to pay a fine every time they make a prediction that doesn’t come true or publish a study that is flawed or biased.  Who do you think would end up being penalized more?

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By John Serpa (Chicago)
on February 27th, 2013


Interesting blog but I have a few questions. I’ve tracked Atlantic hurricanes for 30 years and can you explain to me what cause two hurricanes to strike NYC in the same month in 1955? Or what caused the Great Hurricane of 1938 that smashed the east coast with more power than Sandy?

In the case of the 1938 hurricane there was a blocking high in place. These are rare atmospheric setups and to blame a rather common east coast hurricane in October on global warming has no science to back your claim. Not one peer reviewed meteorology finding agrees either. In fact, this is the longest stretch since record keeping began of the US not having a direct hit from a CAT3 or stronger storm.

Global warming may in fact be occurring, but blaming weather events that occur under the right conditions is being an alarmist and not a scientist.


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By Steve
on March 24th, 2013

Really all this is giving science a bad name and putting on the same level as religion.  When you see sentences like “What is already clear, however, is that climate change very likely made Sandy’s impacts worse than they otherwise would have been.”  Clear based on what???  I’ve lived in this are for well over 40 years and, while it may be a big surprise to some, we’ve always had hurricane and other extreme weather here.  I can remember hurricanes in Baltimore in the 70’s as a child.  Nothing I have seen of recent seems new to me.  What gross irresponsibility in their haste to make political change, they throw facts and the scientific process out the window.

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