

Sandy pressure visualization (SimuAwips)

If Superstorm Sandy, which decimated coastal New Jersey and New York, hit in the year 2100 in a warmer, juicier climate, its toll would be even more devastating. And if Sandy had struck in 1900, when heat-trapping greenhouse gases had not yet begun their steep ascent, it would have been modestly less severe.

Those are the conclusions of Gary Lackmann, a professor of atmospheric sciences at N.C. State University, in a new study suggesting hurricane intensity is sensitive to the amount of greenhouse gases humans release into atmosphere.

Related: The whole truth about Superstorm Sandy and climate change

The study, published online today in the Bulletin of the American Meteorological Society, states a year 2100 version Sandy (hereafter: Sandy 2100) would be “significantly” more intense.

“In conjunction with continuing sea-level rise and coastal development, a future landfall of a stronger Sandy would have the potential to exert a much greater societal and economic impact than did the present-day Sandy,” the study says.

Related: 17 images that tell the story of Sandy slamming the East Coast

Lackmann ran a collection of model simulations to draw this conclusion, using a scenario in which greenhouse gases continue to rapidly increase in the atmosphere. Sandy’s central minimum pressure – a measure of strength – would be 10 millibars (mb) lower, the study says. Lower pressures signal a more intense storm.



Sandy’s simulated minimum pressure given greenhouse gas levels in 1900 (green line), 2012 (blue line), and (projected in) 2100 (red line) during its life cycle, beginning when it was centered in the Bahamas (Bulletin of the American Meteorological Society)

When the real-life Sandy crashed ashore near Atlantic City in 2012, its minimum central pressure was 946 mb – the second-lowest pressure of any storm to make landfall north of Cape Hatteras, N.C. on record. Sandy 2100 might then have a pressure of around 936 mb at landfall, besting the record-setting Long Island Express Hurricane of 1938 which had a pressure reading of 941 mb when it struck land.

“We should be very concerned that a future Sandy-like storm could be substantially worse than what was observed,” Lackmann said in an email.

Lackmann’s study also finds Sandy 2100 would make landfall farther north (see below panel c), due to changes in some of the storm’s steering patterns. In this scenario, the worst of the storm surge flooding would be pushed into southern New England rather than in New Jersey and New York.



The modeled track of Sandy for a greenhouse gas environment in 1900 (left), 2012 (center – when it actually occurred), and 2100 (right) (Bulletin of the American Meteorological Society)

Conversely, a version of Sandy simulated in the somewhat cooler climate of 1900 (hereafter, Sandy 1900), in which greenhouse gases were lower, turned out weaker and made landfall farther south (see above, panel a) than the real 2012 storm, the study finds. But the study is careful to point out the intensity changes for the weakened Sandy 1900 were not statistically significant.

The relative lack of intensity changes found between Sandy 1900 and the actual Sandy leads Lackmann to conclude human-driven increases in greenhouse gases had a “relatively small influence in worsening the [actual] storm.”

James Kossin, a climate researcher at NOAA who was not involved in the study, said Lackmann’s results are “plausible” although he expressed greater confidence in the modeled intensity changes versus the shifts in storm tracks.

“[T]o say that Sandy’s track would change in a specific way due to the thermodynamic changes is definitely very interesting in an academic and hypothetical sense, but should probably not be taken too literally,” Kossin said.

Thomas Knutson, another NOAA climate researcher whose work has shown increases in hurricane intensity as greenhouse gas levels build in the atmosphere, agreed that the results were “at least plausible” in an e-mail.

The study analyzed hypothetical intensity changes starting mid-course in Sandy’s life cycle, when it was centered near the Bahamas – rather than when it formed in the Caribbean. “The question as to whether Sandy would have even formed in a different climate has not been addressed,” the study cautions.

The study also did not evaluate the influence of sea level rise on the storm’s impact which, of all of Sandy’s possible connections to climate change, is thought to be the most direct. As sea levels were roughly one foot lower along the East Coast in 1900, the amount of coastal inundation from a Sandy-like storm at that time would have been less. And, as substantial additional sea level rise is projected by 2100 due to climate warming, sea level rise – along with these “plausible” increases in storm intensity – will likely have significant consequences for coastal areas.

Related: Climate expert: “Washington, D.C. faces significant risk of record high floods”

“These results warrant concern for the future if greenhouse gas emissions aren’t reduced,” Lackmann said. “Additionally, unregulated coastal development, building codes, sea-level rise, and other factors, are probably just as important in future coastal damage mitigation efforts.”