Satellites that monitor tropical cyclones have only been in use for the past 40 years. Prior to that, researchers used observations from ships and aircraft, but those observations did not include the systematic measurements we have today. Despite satellite measurements, researchers still have difficulty predicting the path and severity of hurricanes. However, one thing has become clear, the frequency and strength of hurricanes will continue to increase as the climate warms.
Scientists at the Neils Bohr Institute recently compiled sea level and weather data back to 1923. They found that tropical cyclones typically form in the Atlantic Ocean and travel towards the Gulf of Mexico and the U.S. east coast. Daily tide levels have been recorded for many years, and scientists were able to acquire tide measurements back to 1923. Every time there was a rapid change in sea level, there was also a historical account of tropical storms that made landfall. According to historical data, there has been an increasing trend in the number of major storm surges since 1923.
The overall global temperature since 1923 has increased 0.7 degrees Celsius, with yearly variations. Researchers noted there is an increased tendency for cyclones in warmer years. Extreme storm surges, such as those from Hurricane Katrina, are twice as likely to occur in warm years than cold years. If temperatures rise 3°C warmer, as scientists predict, then we could see a steep increase in the frequency of tropical cyclones on the east coast.
Research at Duke University has shown that the intensity of tropical cyclones may increase as well. High-pressure systems over oceans, which largely determine the track of tropical cyclones in the northern hemisphere, are likely to intensify during this century. As greenhouse gas concentrations in the atmosphere increase there will be an increase in the land-sea thermal contrast. The land-sea thermal contrast is the difference between ocean and land heating as Earth’s climate warms. This change will fuel the intensification of high-pressure systems, which will in turn increase the severity of tropical cyclones to come.