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September 1, 2011 

Hurricane Irene Demonstrates Threats to Coasts As Climate Changes

Every hurricane season, climate scientists are asked how climate change is impacting hurricanes.

The short answer is that global warming makes the ocean warmer and increases sea surface temperatures, which can make hurricanes stronger. But several factors, including differences in wind speed and direction, can break up hurricanes. Many future projections show a decrease in the frequency of all hurricanes globally, but a higher chance of intense hurricanes forming when they do occur. The changing nature of hurricanes in a warmer world remains an active area of research.

In any case, focusing on climate change and hurricanes can obscure the consequences of less sensational climate-related threats to America’s coasts, including sea-level rise and more intense precipitation. Further, extreme weather damage to the East Coast is especially expensive because the area is densely populated and highly developed.

Below, please find scientific and economic background information that sheds light on threats climate change poses to East Coast.

The East Coast is hard hit economically when storms strike

Insured coastal property along Hurricane Irene’s path—from North Carolina to Maine—is valued at $4.9 trillion, accounting for more than half of the value of all insured coastal property in the Gulf and Eastern States.

Even though Hurricane Irene was a Category 1 storm, a preliminary estimate from the Insurance Information Institute found it could inflict $7 billion in damage, which would make it among the 10 most expensive weather-related disasters in U.S. history. The costliest damage related to Irene is expected to stem from claims in some of the most densely populated areas along the East Coast, including New Jersey and New York. The cost of damage from extensive inland flooding in Vermont, New Jersey, Pennsylvania and Virginia is still unclear, but it will likely raise overall damage costs.

Significantly, Irene was the tenth extreme-weather related disaster costing more than $1 billion in the United States this year alone, according to the National Oceanic and Atmospheric Administration’s (NOAA) National Climatic Data Center. Among the other nine were heavy winter precipitation, heavy spring rains, and Southwest droughts, and wildfires, all phenomena more directly linked to climate change.

Sea levels are rising and allowing storms to reach further inland and damage property

Irene demonstrated how storm surges and high tides can make storms more damaging.

More broadly, as sea levels rise due to climate change, storms—including hurricanes—have a higher “jumping off point” when they hit land and are able to penetrate further inland before they dissipate, posing greater risks to roads and buildings.

Sea levels are expected to rise as the ocean warms and expands and as land-based glaciers and ice sheets rapidly shrink. One recent study estimates that total sea-level rise by the end of the century could be between 2.5 feet and 6.6 feet, though scientists consider the worst-case scenario less likely.

What would future sea-level rise mean for coasts? According to research compiled by the Union of Concerned Scientists, in North Carolina, 18 inches of sea-level rise would cause $2 billion in cumulative property damage by 2100. In Boston, 18 inches of sea-level rise would exact cumulative costs of $13 billion by 2100—on top of $7 billion in other expected flooding costs. And if sea-level rise reaches 33 inches by 2100, today’s 100-year coastal flood will likely occur every one to two years in Boston and Atlantic City, and every 11 to 22 years in New York City.

Further, heavier rainfall, sea-level rise and flooding can chip away at barrier islands and wetlands, leaving coastal areas more vulnerable to storms, including hurricanes.

Warmer air increases the chance for more intense precipitation that can drive flooding

Warmer air holds more moisture and climate change is shifting precipitation toward the heaviest storms. Since 1958, the amount of rain or snow falling in the heaviest one percent of storms has risen nearly 20 percent on average in the United States and 67 percent in the Northeast. Heavier rains can drive more flooding. According to the NOAA, flash flooding and river flooding in the United States caused an average of $2.7 billion in property and crop damage annually from 2000 to 2010.

While most studies document an increase in very heavy precipitation since the 1970s, they typically have not isolated the influence on rain associated with hurricanes.  However, high-resolution models that examined the potential impact of climate change on hurricanes project that by the end of this century, precipitation rates could increase, on average, 20 percent within 62 miles of the hurricane center. This is consistent with the consequences of a warmer atmosphere and illustrates the danger to inland areas like Vermont that due to its unique geography has incurred significant flooding in Irene’s wake.

Coastal communities face difficult economic choices

Coastal communities typically endure the cost of recovery from extreme weather, especially if they are unable or unwilling to prepare. They also can invest in preparedness measures to dampen the impact of extreme weather. Other communities, such as a few along the Alaska coast, plan to make the costly move inland.

Preparedness measures, in particular, can bear high costs. For individual property owners, elevating a single-family home by 24 inches could cost $22 to $62 per square foot, while raising larger structures would be far more costly. More broadly, estimates of the cost of protecting vulnerable coastal areas with seawalls vary considerably. One estimate pegs the cost of seawalls for urban areas in the Northeast at $3.4 billion. However, seawalls would be ineffective against permanent flooding caused by sea-level rise without constant pumping of rain and groundwater within the walled areas. Further, vertical seawalls typically enhance erosion on the ocean side, creating higher costs for beach replenishment.

Better preparedness and reducing emissions is our best path forward

Extreme storms are a reminder that our coasts are more vulnerable today than they used to be, as a result of increasing coastal development that puts more people and valuable property at risk. In a warming world, more frequent or more intense extreme weather events could likely make these risks even higher.

As climate change accelerates, local, state and federal agencies will need to update their emergency response plans and budgets to more accurately reflect how climate change is affecting extreme weather. The risk to low-lying areas in New York City from storms and storm surges, for instance, was enough to justify the first-ever mandatory mass evacuation of more than a quarter of a million people there. New York City is already considering other ways it will need to prepare for changing sea levels, more extreme heat and other effects of climate change.

America’s fiscal belt-tightening could also affect disaster preparedness. Cuts to NOAA’s budget may stymie the agency’s ability to accurately track and analyze weather and provide timely warnings that protect lives and property. For instance, NOAA’s proposed National Climate Service, which would have provided local and regional climate data, was blocked in the FY11 spending bill passed by Congress. Now, proposed budget cuts for Fiscal Year 2012 could prevent NOAA and NASA from maintaining and updating their weather monitoring satellite program, which tracks and predicts extreme weather events.

At the same time, economists and scientists see evidence that over the long term, the cost of preparing for the worst consequences of climate change far exceeds the cost of investing in technologies and policies that would dramatically reduce the emissions that are driving climate change. Further, many measures that could reduce emissions such as energy efficiency, fuel efficiency and deploying renewable energy, come with other economic, health and employment benefits.

 

The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet's most pressing problems. Joining with citizens across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future.

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