Today is the first day of Atlantic hurricane season, which runs from June 1 to November 30. Last week the National Oceanic and Atmospheric Administration (NOAA) issued their forecast for the 2017 hurricane season, which indicates that this hurricane season will most likely have above-normal or near-normal activity (45% chance for an above-normal season, a 35% chance for a near-normal season, and a 20% chance for a below-normal season). There will likely be:
- 11-17 named storms, which includes Tropical Storm Arlene in April;
- of which, 5-9 will become hurricanes;
- of which 2-4 will become major hurricanes
These storms will not necessarily make landfall, but it is important to remember that all it takes is a near-hit from a storm to spell disaster. For reference, an average season will see 12 named storms, 6 hurricanes and 3 major hurricanes.
In addition to this day serving as a reminder to make sure your household is prepared for a hurricane, it is also a good time to think about how climate change affects hurricanes and what we can do to mitigate the worst impacts. There are several ways that global warming makes the impacts of hurricanes worse: 1) more rainfall, which means more flooding; 2) higher sea level, which means higher storm surge and more coastal flooding; and 3) potentially increased incidence of major hurricanes.
Global warming causes more rainfall because as the atmosphere warms, it holds more water vapor. When a tropical cyclone or hurricane forms, it gathers the water vapor from a large area and dumps it. How does this play out? One study found that between 1994 and 2008, the Southeast suffered from a 40 percent increase in rainfall in the heaviest rainfall events because of tropical cyclones.
The sea level rises due to global warming for two reasons: 1) as the ocean heats up, it expands; and 2) melting land-based glaciers flow into the ocean. Globally, the sea has risen about 8 inches over the past century, but global warming is increasing this rate of rise. In recent years, the rate of sea level rise has doubled or tripled and it is expected that global sea levels will rise 1 to 4 feet–but as much as 8 feet over the course of this century, depending on how swiftly we act to reduce carbon pollution. When tropical storms or hurricanes arrive onshore, they push water inland, raising the sea level often multiple feet. Storm surge itself can be catastrophic, but storm surge plus a couple additional feet of height added by sea level rise would greatly amplify the destructive potential. As the sea rises from higher temperatures, each storm pushes flood waters higher than it would have without sea level rise. For example, insurance giant Lloyds of London estimated that about 30 percent of the New York City area losses from Hurricane Sandy were attributable to just the historical observed sea level rise. and other scientific analysis has estimated that just the 8 inches historic sea level rise meant that Sandy affected an additional 27 square miles, hitting 83,000 additional homes. Put another way, the damages from Hurricane Sandy in New York City would have been 30 percent less and tens of thousands of homes would have been spared from flooding in the absence of sea level rise.
Finally, we have to consider how global warming affects the strength of the storms themselves. According to the National Oceanic and Atmospheric Administration (NOAA), we are likely to experience an increase in hurricane storm intensity, with a doubling of category 4 and 5 hurricanes over the course of the 21st century, while at the same time a decrease in frequency of category 1 to 3 storms. It is projected that storm intensity will increase 2–11 percent and there will substantially higher rainfall rates than present-day hurricanes—perhaps 10-15 percent more rainfall within 100 km of the storm center. Overall, it is projected that hurricane damages will increase by 30 percent by 2100, without even taking into account future sea level rise.
While climate change is making hurricanes worse, there is much we can do to prevent worst case scenarios. We must as individuals and as a society reduce pollution that causes climate change. So as you make sure your household is prepared for hurricane season, think about how you might help proactively prevent disaster down the line. See tips on what you can do to fight global warming here.