Increases in Hurricane Frequency

Contributing Factors

• Certain variables could lead to increases in hurricane frequency. Among the most major is sea surface temperatures. Hurricanes require warm ocean waters above 26.5 degrees Celsius (80 degrees Fahrenheit) in order to form. There is a known correlation between tropical sea surface temperatures and hurricane frequency, strength and duration. For instance, it is estimated that hurricane wind speeds could increase up to 5 percent with every 1 degree Celsius (1.8 degrees Fahrenheit) rise in tropical ocean temperature. And since about 1970, sea surface temperatures have risen in all of the oceans in which hurricanes can form. Other factors that could affect increases in hurricane frequency include air temperatures in the upper atmosphere and wind shear, both of which would actually act to inhibit hurricane development. The power struggle among these opposing forces could have consequences on hurricane potential.

Frequency Vs. Intensity

• Contrary to prior studies, the most current research has shown that the overall annual number of hurricanes worldwide is not increasing. Similarly, the average number of hurricanes forming only in the Atlantic basin isn̵7;t rising, either. There is, however, evidence that those hurricanes that do form tend to be more powerful; specifically, the number of Category 4 and Category 5 hurricanes -- the strongest types -- are on the rise. Additionally, many hurricanes are intensifying more rapidly than in the past, attaining higher wind speeds in shorter amounts of time. These increases in intensity are likely at least partially attributable to the corresponding rises in sea surface temperatures.

Influence of Technology

• It is understandable that people have thought hurricanes have been occurring with greater frequency in recent centuries. Perceived increases, however, are due to advances in technology. Although record keeping extends back to the 19th century, detection systems were lacking; as late as the early 20th century, hurricanes at sea were known of only through shipping reports. In the 1940s, monitoring via aircraft reconnaissance began, but it did not cover all regions. Satellite imagery, which displays hurricane presence and intensities, wasn̵7;t widely available until the 1960s and 1970s. Thus, prior to the advent of satellites, many hurricanes were ̶0;missed,̶1; especially those of short duration and those that spent their entire lifetimes over the open ocean, never making landfall.

Human Influence and Future Impacts

• Human activities, particularly greenhouse gas emissions, have likely attributed to rising ocean temperatures and the related climactic changes that influence hurricane development. These impacts will continue so long as humans keep using copious amounts of fossil fuels as energy sources. As the seas continue to warm further, hurricanes that form will have a greater probability of being more intense, although the overall volume of hurricanes will likely remain unchanged. Additionally, these hurricanes will probably also possess higher rainfall rates, leading to worsened flooding upon landfall. On the whole, stronger hurricanes will produce greater destruction if and when they strike land.