FUTURE: floods and storms in New London County

11/14/2017

Changes to the New London County coastline under two different emissions scenarios. Source: Climate Central Surging Seas: Mapping Choices.

Climate changes and the local environment:

Mean global sea levels have risen by at least 17 centimeters (nearly 7 inches) in the twentieth century. Yet regional variations in ocean temperatures, prevailing winds, ocean currents, and the rise or fall of Earth's crust mean some areas have experienced, and will experience, greater sea level increases than others. Off Connecticut, for example, sea levels are today increasing more quickly than the global average. Connecticut is in fact sinking as its crust slowly recovers from the immense weight of glaciers that covered it during the last ice age. Connecticut is sinking by over 0.03 inches per year, even as Earth's ocean rise.

Rising sea levels and sinking land will have dire consequences for the environment of New London County in Connecticut. Low-lying coastal lands in and around the county will eventually be inundated, overwhelming natural flood and storm barriers such as beaches and wetlands. That will make the county ever more vulnerable to coastal storms and flooding, which will grow more frequent and severe as Earth's climate warms.

In fact, the Connecticut Governor’s report predicts that by 2050, New London County may face a 100-year storm every 56 years. A 100-year storm refers to a storm of such rarity and magnitude that it has only a 0.1 percent chance of happening in New London County in any given year.

Meanwhile, precipitation is on the rise in New London County as local temperatures warm. Hotter air holds more water vapor than cold air, so it is no surprise that average annual precipitation is increasing, while extreme precipitation events - such as torrential rains - are growing more frequent. Both trends are expected to accelerate in the future.

Stronger storms sweeping in from the sea are therefore projected to bring more coastal floods in the warmer future, while heavier rains lead to more river floods in New London County.

Past and projected changes to the daily high in New London County. Red shows the projection for a future with higher emissions, and blue with lower emissions. Source: NOAA U.S. Climate Resilience Toolkit (Climate Explorer).

How we know:

These predictions are based on four easy to use tools that are freely accessible online: National Oceanic and Atmospheric Administration (NOAA) Sea Level Trends app, the NOAA Climate Explorer app, and the Climate Central Surging Seas, Mapping Choices app, and the Aqueduct Global Flood Analyzer.

The Sea Level Trends tool shows regional mean sea level changes from the twentieth century through today. NOAA collects data for these measurements through the 142 long-term tide stations of the National Water Level Observation Network, which has been measuring sea level for over 150 years. Each regional mean sea level rise or fall is computed using a minimum of 30 years of data to ensure accuracy.

The Climate Explorer tool uses weather information recorded by meteorological instruments at weather stations to reconstruct past climate changes. It uses supercomputer simulations of future climate changes under both high and low emissions scenarios.

The Surging Seas tool combines historic flood statistics and local sea level trends with global scenarios of sea level increases, which were compiled in the 2014 U.S. National Climate Assessment. The Global Flood Analyzer estimates the vulnerability of regions to flooding, providing figures for the cost of flood damage and number of people affected.

Past and projected days, per year, with more than one inch of precipitation in New London County. Red shows the projection for a future with higher emissions, and blue with lower emissions. Source: NOAA U.S. Climate Resilience Toolkit (Climate Explorer).

Human consequences:

New London County is already coping with climate change. In 2010, New London endured a 100-year flood after heavy rains caused rivers to spill their banks and ground water to overflow sewage systems. The Federal Emergency Management Agency (FEMA) estimated that the flood cost the county $5.3 million in losses and damages. Precipitation trends will make such floods more common.

In New London County, a total of 4,306 residents currently live in homes that are less than 6 feet above sea level. By 2030, there is a 67% chance that flood with waters 6 or more feet above sea level will occur, which would put all these lives and homes at risk.

Increased intensity and frequency of both coastal storms and flooding is hugely detrimental to infrastructure and business in New London County. In particular, the Naval Submarine base and the General Dynamics Electric Boat Corporation submarine construction yard, which is the primary builder of submarines for the U.S. Navy, are at risk from sea level rise, storms, and flooding. These establishments are essential to the county’s economy and to national security. Re-engineering of the base and the submarine construction yard may be necessary in order to keep them functional in the face of rising sea levels, yet this would be staggeringly expensive.

The consequences of climate change and global warming have already harmed many of coastal communities in New London County. Under all future emissions scenarios, even very optimistic ones, further damage is all but inevitable.