Climate and Weather
By weather.com meteorologists
4 days ago
At a Glance
- Hurricanes are becoming stronger as Earth's climate continues to warm.
- The probability of major hurricanes (Category 3 or higher) has increased in the last 40 years.
- The North Atlantic Ocean showed high rates of increase in hurricane intensity from 1979 to 2017.
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Climate change is making tropical cyclones more intense with stronger maximum sustained winds, according to a study led by scientists at NOAA and the University of Wisconsin-Madison Cooperative Institute for Meteorological Satellite Studies (CIMSS), who analyzed nearly 40 years of enhanced infrared satellite imagery.
This study, published in the Proceedings of the National Academy of Sciences (PNAS), found a significant increase in tropical cyclone intensity across the globe over the period from 1979 to 2017.
A tropical cyclone is a low-pressure system with an organized circulation and concentrated shower and thunderstorm activity. It is commonly called a hurricane, cyclone, typhoon, tropical storm or tropical depression, depending on its strength and the ocean basin in which it is located.
The research builds on lead author James Kossin's previous work from 2013, which identified trends in tropical cyclone intensity over a 28-year period spanning from 1982 to 2009. However, Kossin noted that initial dataset was less conclusive and more hurricane case studies were needed to provide statistically significant results.
This new study added about 10 years of additional satellite data to Kossin's 2013 paper. The Earth-orbiting satellites measured numerous features of a tropical cyclone, including infrared temperatures above the eyewall, to estimate its intensity. The researchers utilized techniques that accounted for differences in the data that are caused by advances in technology over time, such as higher-resolution imagery from new satellites, like GOES-East and GOES-West.
The longer period of study allowed statistically significant global trends in hurricane intensity to be identified by Kossin and his team. The research supported the connection between Earth's warming surface temperatures and stronger tropical cyclones more significantly than his previous work.
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Most notably, the study found an increase in the proportion of major hurricanes – those that are Category 3, 4 or 5 intensity on the Saffir-Simpson Hurricane Wind Scale – compared to Category 1 or 2 tropical cyclones. Between the early and latter halves of the 39-year dataset, "there is a clear shift toward greater intensity that manifests as increased probabilities of exceeding major hurricane intensity," the study said.
The researchers discovered that the probability of a tropical cyclone having Category 3 or higher wind speeds (at least 111 mph) increased by about 15% between the first and last halves of the analyzed satellite data. This corresponded to about an 8% increase per decade over the period of study. The proportion of all tropical cyclones exceeding major-hurricane intensity showed a similar increase of about 6% per decade.
Kossin and his co-authors categorized the data by location to address the regional variability around the globe. The North Atlantic Ocean, along the hurricane-prone East Coast of the United States, showed high rates of increase in hurricane intensity from 1979 to 2017.
"The greatest changes are found in the North Atlantic, where the probability of major hurricane exceedance increases by 49% per decade," the study said.
However, the authors noted that regional variability in the North Atlantic – due to factors such as the Atlantic meridional overturning circulation (AMOC), aerosols, African dust, volcanic activity and greenhouse gases – made it difficult to fully understand the trend. In addition, the magnitude and significance of the trends among individual ocean basins varied considerably, according to the study.
"Our results show that these storms have become stronger on global and regional levels, which is consistent with expectations of how hurricanes respond to a warming world," Kossin said in a University of Wisconsin-Madison news release. "It’s a good step forward and increases our confidence that global warming has made hurricanes stronger, but our results don’t tell us precisely how much of the trends are caused by human activities and how much may be just natural variability."
Algorithms by NOAA's National Centers for Environmental Information (NCEI) indicate that most of the years this decade are very likely to rank among the 10 warmest years. What's more, hurricanes rank as the costliest U.S. weather and climate disaster. Therefore, it's important to understand the potential impacts climate change will have on hurricanes in the future.
