Is Hurricane Frequency Increasing?
100 years ago, the number of hurricanes in the Atlantic may have been less than they are today according to one study by Greg Holland of the National Center for Atmospheric Research (NCAR) and Peter Webster of Georgia Institute of Technology. The cause? The study indicates climate change may be the culprit.
The analysis identifies three periods since 1900 during which the average number of hurricanes and tropical storms increased dramatically and then remained elevated. The first period, between 1900 and 1930, saw an average of six Atlantic tropical cyclones of which four were hurricanes and two were tropical storms. From 1930 to 1940, the annual average increased to 10, consisting of five hurricanes and five tropical storms. In the final study period, from 1995 to 2005, the average reached 15, of which eight were hurricanes and seven were tropical storms.
Why is global climate change to blame? The answer may be with sea surface temperatures. Globally, temperatures in the oceans have risen by about 1.3 degrees Fahrenheit in the last century. Many would argue that the increases are a result of a natural cycle in oceanic and atmospheric temperatures. Still others point out the fact that direct climate records do not extend far enough into the past. Even the study reports that increases in modern technology have some effect on the data, but the authors caution that enhanced observations in recent decades cannot account for all of the increases in hurricane frequency. Interestingly, to observe storms in the Atlantic more systematically, meteorologists began relying on data from aircraft flights in 1944 and weather satellites about 1970. The distinct transitions in hurricane activity noted by Holland and Webster occurred around both 1930 and 1995.
While the number of storms has steadily increased, the proportion of hurricanes to all Atlantic tropical cyclones has remained steady. Hurricanes have generally accounted for roughly 55 percent of all tropical cyclones. However, the proportion of major hurricanes to less intense hurricanes and tropical storms has oscillated irregularly, and has increased significantly in recent years.
Read more in the original report Heightened Tropical Cyclone Activity in the North Atlantic: Natural Variability or Climate Trend?
Comments
Any comparison of hurricanes over the years is flawed.
Before weather satellites pretty much the only hurricanes recorded were the ones that reached land. Even using shipping and airplane records the count of hurricanes was inexact.
Now with weather satellites we are able to see and track hurricanes all over the globe. So of course the number of hurricanes counted will increase.
To make a reasonable comparison of hurricane activity you must only count hurricanes that reach land, where they would have been counted before weather satellites.