Trends: socio-economic, climate change
The precipitation in New York is likely to increase by 5-10% by the 2080s. Much of this additional precipitation is projected for the winter months. Because of the effects of higher temperatures, New York also faces increasing risks of droughts. Although the percentage change in regional precipitation is expected to be relatively small, larger percentage increases are expected in the frequency, intensity, and duration of extreme precipitation events at daily timescales. Moreover, by the end of the 21st century, increases in temperature are expected to outweigh increases in precipitation, resulting in more droughts.
In December 1992 a storm produced the worst flood in Metropolitan New York in over 40 years. The water level at the Battery in Lower Manhattan peaked at 2.4 m above mean sea level. Flooding of lower Manhattan, together with near hurricane force wind gusts, led to an almost complete shutdown of the New York City transportation system. Many seaside communities in New Jersey, Connecticut, and Long Island had to be evacuated.
This storm showed the vulnerability of the Metropolitan New York – New Jersey – Connecticut transportation system to major northeastern storms and hurricanes. Most of the area’s rail and tunnel points of entry, as well as airports, lie at a critical elevation of 3 m or less. Flood levels of only 0.30-0.61 m above those of the December 1992 storm could have resulted in massive inundation and potential loss of life. The vulnerability of the regional transportation system to flooding was demonstrated again in August 1999, after 6.4-10.2 cm of rain fell in the New York metropolitan area, nearly paralyzing the transportation system. With future sea level rise, even less powerful storms could inflict considerable damage.
In 2011 New York faced a major threat by the tropical storm Irene. The city had to evacuate 340.000 people living in low lying areas and the public transport system had to be shut down.