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Warmer, Colder, Wetter, Dryer: How Climate Change Will Affect NYC

At a time when waterfront property in New York City has never been more popular, climate change may pose an ever-greater threat to the city’s infrastructure and developments, according to the “Special Issue: Advancing Tools and Methods for Flexible Pathways and Science Policy Integration,” the third report from the New York City Panel on Climate Change (NPCC). Previous overviews were issued in 2001 and 2010.

“Projected increases in the frequencies and intensities of extreme events pose particular challenges to New York City,” the report said. “The climate extremes considered in NPCC3 are extreme heat and humidity, heavy downpours, droughts, extreme winds and cold snaps, as well as sea level rise and coastal flooding.”

Already, sea levels are rising, and the city is experiencing hotter summers, warmer winters and more frequent bouts of intense precipitation, noted the report, which covers 31 counties across New York State, New Jersey and Connecticut.

“While urban areas like New York City and its surrounding metropolitan region are key drivers of climate change through emissions of greenhouse gases, cities are also significantly impacted by climate shifts, both chronic changes and extreme events,” write NPCC Co-Chairs Cynthia Rosenzwieg and William Solecki. “These are already affecting the New York metropolitan region, and will increasingly do so in the coming decades.”

The waters surrounding New York have been rising since the 19th century. Sea level at the Battery has been rising at a rate of 0.11 inches per year since 1850, a higher-than-global average because of the region’s ongoing land subsidence as ice age glaciers retreat and ocean waters continue to warm. Now, the report noted, the melting of Antarctica is contributing as well, and the report projects up to a 6.75-foot sea level rise in the 2080s and a 9.5-foot rise by 2100.

If the city experiences sea level rises on the high end, “monthly tidal flooding will begin to affect neighborhoods around Jamaica Bay by the 2050s and many other areas by the 2080s,” the report said, with lower-income, more heavily African-American and Hispanic areas prone to hazards.

Also in danger is critical infrastructure: Many of the city’s 62 hospitals are in danger of flooding, including three located along the East River. And even if greenhouse gas emissions are reduced and stabilize, the sea levels around the region are expected to rise into the 22nd century, the report continued.

“The vulnerability of these facilities to climate-related extreme events is shown by the impacts that Hurricane Sandy had on them in 2012. Five acute-care hospitals shut down in New York City due to Hurricane Sandy, and there were substantial delays in returning to normal functioning,” the report said. “Adaptation planning with consideration of hospital capacity and lifeline infrastructure in vulnerable areas will be essential for minimizing costs and damages to health institutions during and after future extreme weather events.”

Flooding is not the only concern the report raised. “Extreme events,” including heat waves, heavy downpours and more will pose serious dangers to infrastructure, which is already under pressure from other factors including age, deterioration and other construction. Central Park’s average temperatures have risen 0.2Fahrenheit per decade from 1900 to 2013. Since 1970, annual average daily maximum summer temperatures have been rising at rates of 0.5F per decade at JFK Airport and 0.7F per decade at LaGuardia Airport. Meanwhile, days below freezing decreased at a rate of roughly 1.9 days per decade with about 22 fewer days below freezing in 2017 than in 1900.

In addition, humidity is projected to increase by more than 30 percent from baseline values, which should have major effects on public health and energy demands. Managers of the city’s water supply will also face increasing challenges as flooding affects pumping stations, treatment facilities and inflow/outflow sites. While New York City appears to be prepared to respond, smaller systems in the region could be overwhelmed, according to the report.

Current projections call for one additional yearly heat wave every 20 years until 2060, when growth slows. But that may not be because of a plateau.

“This may be due to consecutive events coalescing into very long heat waves, which becomes more likely as heat waves increase in length and frequency,” the report continued. By the 2080s, projections show anywhere from 24 to 75 days above 90 o Fahrenheit yearly, versus 10 days in the years from 1971 through 2000.

Heavy downpours (defined as rarely occurring rainfall at less than daily timescales that can produce urban flooding) are projected to increase from the average 13 days of rain of more than 1 inch annually from 1971 to 2000, to as many as 16 days in the 2020s.

To combat this, the report recommended that the city establish a pilot climate indicators and monitory system; that the NPCC coordinate with other regional organization to conduct integrated climate assessments; and that the city and NPCC conduct a climate summit event during the next mayoral term to bring together scientists, practitioners, decisionmakers and stakeholders. The report also suggested that the region continue to monitor sea level rise and the processes contributing to the increase, especially for its long-term (extending even to the year 2300) impact on infrastructure.

“New York City is representative of the kinds of climate change challenges that may be experienced by other cities around the world, especially those located in emerging metropolitan conurbations,” wrote Rosenzwieg and Solecki, noting that New York is communicating with other cities including London and Amsterdam regarding responses to climate change. “How the region is impacted by global climate change and how it will respond to the many-faceted challenges may be seen as a bellwether for other similar urbanized regions in both developed and developing countries.”

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