What a storm 10 years ago could look like 30 years from now

It has been ten years since Hurricane Sandy devastated the New Jersey/New York area. The storm was responsible for $65 billion of economic damage in the U.S., according to the official NOAA Report (2013). Decadal remembrances of such significant storms serve to remind the (re)insurance industry what storms were capable of in history and to prepare better for future renditions. That is especially true when climate change factors into the recipe. This anniversary article pays homage to Hurricane Sandy by helping us understand how much worse a storm like it could be in the future.

A Category 1 superstorm

Hurricane Sandy made landfall with maximum sustained winds of 80 mph, a modest Category 1 storm. But that metric alone does not begin to acknowledge how the storm outperformed those winds in terms of damage.

There is no question that Sandy was a large storm in terms of area, at one point spanning 1000 miles in diameter with at least tropical storm force winds. Although there are no specific criteria for the term superstorm, it is likely that the size, moderate Category 1 strength at landfall, and impact to a highly populated area primarily from storm surge resulted in the moniker that is sometimes used for Sandy’s title.

But two other features likely contributed to its superstorm status. One is that in addition to the wind and storm surge damage, Sandy dumped over one foot of rain in some places. More impressively, because of its autumnal appearance, Sandy also generated two to three feet of snow across the central Appalachians. This caused roofs to collapse as well as numerous power outages from downed trees that succumbed to wind and snow more easily because fall foliage season was still in effect.

One other unique aspect was Sandy’s track: the famous left hook that directed it westward toward the New York City area instead of the typical recurve out to sea. The cause of the left hook is significant. All the ingredients came together at once: high pressure, low pressure, hurricane, high tide, sub-freezing air. Sandy was considered to be a/the perfect storm; yet another moniker in the descriptive vocabulary.

The climate-change variable

The Intergovernmental Panel on Climate Change (IPCC) stated in its latest Report the indisputable fact that anthropogenic burning of fossil fuels has caused the planet to warm, including raising ocean temperatures and sea levels. Some studies have suggested climate change helped Sandy to track farther north and be more intense because of the warmer water and also to turn left into New Jersey because of changes in flow patterns. And, it is estimated that $8 billion of the storm surge loss from Sandy was directly attributable to higher sea levels from climate change.

According to current naming conventions, there will likely never be another Sandy, and there could certainly be another storm like Sandy in the future. While the exact trajectory of future climate change is uncertain, sea level will likely continue to rise for at least another hundred years, even if we were to stop altogether burning fossil fuels today. And ocean surface temperatures will likely continue to increase globally in all but the most optimistic climate-change scenarios as we will likely see at least another degree Celsius of warming.

Unfortunately, it is also still possible that an increase of another two degrees Celsius could occur by mid-century, yielding a Sandy-like storm that could be 10% stronger.

Verisk recently released a set of climate change influenced simulations of Hurricane Andrew, considering all sub-perils, and demonstrated that by 2050 under an RCP 8.5 climate scenario, the impact to wind loss would likely dominate impacts to precipitation induced flood and storm surge losses from an absolute standpoint even when accounting for sea level rise (SLR). Verisk also recently conducted a study on how climate change could influence hurricane activity over the entire U.S. by mid-century. As part of the study, it looked at how storm surge losses would likely change from increases in sea level. For the New York City region, the study found that eight additional inches of sea level rise alone would likely increase the average annual loss by 29%, and combined with expected changes in storm activity, the average annual storm surge loss could increase by 64%. For a two-foot increase in sea level, the percentages increased to 81% (just SLR) and 148% (including changes in storm activity) respectively.

Verisk also obtained more specific estimates of how climate change could impact a re-occurrence of Sandy by examining the Verisk Hurricane Model for the U.S. to find events similar to Sandy 2012. It then used the information from Lackmann (2015) as well as that from Verisk’s 2020 study to determine the loss from similar events but ones that were 10 mb stronger making landfall on Long Island with an additional one-foot of sea level rise. The results suggest an increase in wind loss of about 50% and an increase in storm surge loss of about 70%, the latter being the combined effect of stronger winds piling up more water from already higher seas.

Hurricane Sandy taught us all many lessons. Even when catastrophe models include events like Sandy from a meteorological and climate standpoint, it can still be surprising and catastrophic when extreme events that could happen actually do. They are not simply some theoretical constructs. The potentially disproportionate increase in storm surge losses from another Sandy-like event at mid-century suggests the need for continued resiliency efforts to mitigate coastal flooding if not to mitigate climate change outright.

Hopefully, the lessons from 10 years ago have been truly learned so that in another 30 years time, when a storm like Sandy that could happen does, we have all benefitted from the preparation in the interim.

Dr. Peter Sousounis (peter.sousounis@verisk.com) is a vice president and director of climate change research at Verisk Extreme Event Solutions in Boston, Mass.

See also:

• CoreLogic’s final Hurricane Ian estimate projects $41B-$70B in damages
• Hurricane threat shifts to Eastern U.S. as Gulf Coast dodges a strike
• Playing offense on climate: The opportunity for insurers