Global warming causing more powerful hurricanes

The number of hurricanes are increasing and global warming is to blame, say scientists.

Staff | May 20, 2020

Hurricanes are getting stronger as the world gets warmer, according to a new analysis.

Studying how hurricanes have changed over decades is difficult. The technological tools scientists use to study them changes constantly, making comparisons from different time periods hard to correlate. While research has generally suggested that global warming would result in more powerful and erratic hurricanes, it has been difficult to document with any degree of scientific certainty. Until now, that is.

A new study of hurricanes published May 18, 2020 in the journal Proceedings of the National Academy of Sciences, covers a period of 39 years from 1979 to 2017. Looking at the entire four-decade span and normalizing the data, researchers found a clear trend: storms are getting stronger and major tropical cyclones are occurring more frequently.

The 39-year period of the study overlaps a period when climate change has dramatically accelerated, according to reports by the National Oceanic and Atmospheric Administration (NOAA). The earth's temperature has increased each year in the past 39 years, including eight of the 10 warmest ever recorded. 2018 and 2019, too recent to be included in the study, were also the warmest on record.

"The main hurdle we have for finding trends is that the data are collected using the best technology at the time," James Kossin, a NOAA scientist and University of Wisconsin-Madison professor, said in a statement. "Every year the data are a bit different than last year, each new satellite has new tools and captures data in different ways, so in the end we have a patchwork quilt of all the satellite data that have been woven together."

To create a consistent record, researchers removed the edges from newer, sharper tropical cyclone images to fit an older standard: images where each pixel represents a 5 square mile area (8 sq/km), taken once every three hours. They also excluded newer satellite images of storms using angles not available in 1998. The remaining dataset includes roughly 225,000 similar-quality images of some 4,000 global tropical cyclones stretching back to the 1980s.

Using the images of tropical cyclones to estimate wind intensity, measured in kilotons, researchers found that the chances of a tropical cyclone becoming a hurricane (sustained winds of 74 mph/119 km/h or higher) have increased significantly over the past 40 years. In addition, the odds of major hurricanes (100-knot storms) have gone up by about 15%, with most of that increase occurring in the last 19 years of the 39-year study period.