Last night, I headed down to the beautiful Bell House in the Gowanus section of Brooklyn for this month's Secret Science Club lecture. This month's lecture featured physicist and atmospheric scientist Dr Adam Sobel of Columbia University. Two years ago, Dr Sobel delivered a lecture on the science of Superstorm Sandy in the aftermath of the storm. On the two-year anniversary of Sandy, he returned to the Bell House to discuss people's reactions to scientific predictions.
Dr Sobel jumped right into the topic, showing a slide depicting the October 24th GFS forecast, a deterministic model of weather conditions. This particular model showed that the jetstream had dipped far south, and the 10/24 model produced by the European Centre for Medium-Range Weather Forecasts was an accurate model of the actual course of the storm. On the Wednesday before the storm hit the NY metro area, models indicated uncertainty about the eventual landfall- storms are chaotic systems so slight changes in the characteristics will result in larger eventual changes. On Thursday, the five-day forecast produced by the National Hurricane Center was dead-on. Dr Sobel noted that weather forecasts are great scientific achievements resulting from steady progress. Better computers allow forecasters to make better models, therefore they make better predictions.
When Sandy made landfall, it was a post-tropical storm- it was by no means a weaker storm, but it lacked the symmetry typical of tropical cyclones. Tropical storms are symmetrical and are warm at their center, they gain their energy from the warmth of the ocean. Winter storms are asymmetrical and get their energy from the jet stream- the temperature difference between the pole and the equator give them energy. Sandy was cold at the center- the storm was a merging of a tropichttp://www.nydailynews.com/news/national/national-hurricane-center-warning-system-article-1.1308130al storm and a winter storm. The wind speed was 65 knots, which placed it firmly in Category 1 of the Saffir-Simpson scale. The storm was vast, with a huge area of winds and a worse storm surge. Because the storm was post-tropical, the National Hurricane Center did not issue hurricane watches or warnings north of Virginia. Under NOAA's rules, a hurricane advisory could not be issued due to the nature of the storm, a policy which has been changed. Gale warnings were made, though. On 10/27, then-mayor Michael Bloomberg held a press conference urging New Yorkers to stay indoors and to avoid low-lying areas, while warning of MTA shutdowns.
Sandy was characterized by its dramatic storm surge, basically a slow pileup of water. While the local officials did many things right, they did not issue evacuation orders on Saturday due to the lack of hurricane advisories. Dr Sobel noted that the water gets high no matter what the storm is called. NOAA's current policy is to issue hurricane warnings even if dangerous storms are not technically hurricanes.
On Sunday, 10/28, evacuation orders were given for evacuation zone "A" and the transit system was shut down. There were attempts to protect infrastructure- the electrical signals in threatened subway tunnels were ripped out and certain adits to the system were boarded up. There was a partial pre-emptive shutdown of the power grid. No evacuation orders were given to nursing homes.
Ultimately, Sandy resulted in 117 deaths in the U.S. and 50-65 billion dollars in economic damage. Most of the loss of life occurred in low-lying areas such as barrier islands, which Dr Sobel characterized as "glorified sand dunes". Among the slides depicting the destruction wrought by the storm, a picture of Mantoloking, NJ was particularly scary, as was a photo of the Hoboken, NJ PATH station.
A perusal of the NYC inundation map reveals that every area that flooded was wetlands, landfill, or barrier islands. Dr Sobel noted that the original coastline of lower Manhattan was Water St. He wryly noted that the idea that there would be flooding in Lower Manhattan shouldn't have been shocking.
Two of the worst-hit areas were Breezy Point in Queens, which was ravaged by a wildfire as well as by flooding, and Staten Island's Oakwood Beach.
Half of Manhattan was affected by a power outage and there was substantial flooding as a result of a fourteen foot storm surge. Gasoline supply chains were disrupted for weeks in the region.
Wise short-term decisions that saved many lives and much property were made, such as zone A evacuations and the measures taken to protect the subway system. The region's infrastructure, though was unprepared to withstand the storm... the South Ferry subway station, renovated in 2009, was totaled, needing $600 million dollars in repairs.
Dr Sobel then went over damage estimates from old storms, mentioning a 1992 nor'easter which flooded PATH stations. In 2011, Hurricane Irene resulted in flooding, mainly in New England and upstate New York.
Sandy was a rare event, but no scientific assessment indicated that it was an impossible event. The timing of Sandy was particularly bad- the fourteen foot storm surge coincided with a five foot high tide. In contrast, the thirteen foot storm surge from the 1821 hurricane which hit NYC hit during low tide.
Dr Sobel then brought up the role of availability bias in our reaction to storms. If a particular issue isn't pressing, people tend not to pay much attention to it. If something happens all the time, there's no need to really think about our responses to it, it becomes the "new normal". It often takes catastrophic events to inspire actions meant to mitigate damage.
He brought up the Dutch response to the 1953 Delta Flood which resulted in approximately 1800 deaths and massive economic damage. The Dutch government responded with the "Delta Works", a system of flood barriers. The Thames flood barrier was modeled on the Dutch Delta works. In 1938, the hurricane known as the Long Island Express slammed into the Northeast, resulting in approximately 600 deaths. The estuary cities of Stamford, CT, New Bedford, MA, and Providence, RI were flooded. In the 1960's a hurricane barrier was built to protect Stamford.
Dr Sobel touched on plans to protect New York City from flooding, asking "What will happen post-Sandy?" He brought up PlaNYC, a blueprint for stability and resiliency for the city. He noted that there were no plans for great storm surge barriers in New York harbor- the plan relies on local flood walls and the elevation of infrastructure.
The lecture then moved on to the topic of climate change. Dr Sobel noted the Bloomberg headline: "It's Global Warming, Stupid." He noted that it's hard to pin one storm on climate change. Human influence is not clearly detected in any upward trend in storms- there is a lot of natural variability. Currently, it is thought that climate change may result in fewer tropical cyclones, but that the intensity of storms is likely to increase, on average. Little is known about storms like Sandy, which was peculiar due to its route and its tropical/winter storm hybridization. There is a clear link between global warming and sea level rise, though. This has a bearing on flooding- in the old Saffir-Simpson hurricane scale, each category of storm was typically categorized by three feet of storm surge. Sandy, however, was characterized by Category 1 winds and a Category 3 storm surge. With climate change, it's not unreasonable to jack up storm surge predictions one category. With sea-level rise, weaker storms will still result in higher surges.
Dr Sobel then stated that willful denialism of climate change is the most acute problem that we face in reacting to storms. Denialism makes taking long-term steps and unfamiliar risks to deal with storms. Availability bias is as much of a hindrance as a help. We can't wait for the problem to be compounded, though. He then ran down a quick summary of long-term predictions about weather events- the effect of climate change on tornadoes is largely unknown, but heat waves will definitely be more frequent, as will be coastal flooding. Climate change will probably simultaneously result in more droughts and more flooding. We will probably have fewer snowstorms.
The Q&A after the lecture was short and fast, and the Bastard in the audience didn't get to blurt out a question (for the record, he also had to pee like a racehorse by lecture's end). There was an interesting question about the lack of tropical cyclones in the Southeast Pacific and the South Atlantic- the climate is just not right for cyclones to form, a cold sea surface and strong wind shear combine to prevent this from occurring.
After the lecture, Dr Sobel was signing copies of his new book, Storm Surge: Hurricane Sandy, Our Changing Climate, and Extreme Weather of the Past and Future. The lecture itself was another triumph for the Secret Science Club- a timely exploration of a topic which has been on the minds of many New Yorkers, two years after one of the worst disasters the region has ever faced.