New research has shown that changes in hurricane activity are caused by earlier warmer oceanic conditions due to climate change.
Research, co-authored by a University of Hawai‘i at Mānoa atmospheric scientist, has revealed that since the 1980s hurricane activity has changed, with Category 4 and 5 hurricanes arriving three to four days earlier with each passing decade of climate change.
Hurricanes are one of the most devastating natural disasters in the world, bringing about torrential rains, destructive wind, floods, and coastal storm surges.
When the activity of these events changes, it has significant implications for disaster response preparedness.
“When intense tropical cyclones occur earlier than usual, they cause unexpected problems for communities,” said Pao-Shin Chu, atmospheric sciences professor in the UH Mānoa School of Ocean and Earth Science and Technology and Hawai‘i State Climatologist.
“Moreover, the earlier advance of these storms will overlap with other weather systems, for example local thunderstorms or seasonal monsoon rainfall, and can produce compounding extreme events and strain the emergency response.”
The study, ‘Seasonal advance of intense tropical cyclones in a warming climate,’ is published in the journal Nature.
Little is known about the changes in seasonal hurricane activity
Changes in many characteristics of intense hurricanes are well-studied. For example, the number, intensity, and life span of a hurricane.
However, there is little research on the changes in the seasonal cycle of these events.
Because of this, the team used satellite data, historical tropic cyclone tracks, NOAA rainfall records, and statistical methods to track the seasonal shift in hurricanes.
Significant shift of seasonal hurricane cycle
The researchers discovered that there had been a significant shift of hurricanes from autumn to summer months since the 1980s in most tropical oceans.
The effect was particularly observed in the eastern North Pacific off the coast of Mexico, the western North Pacific, the South Pacific, the Gulf of Mexico, and the Atlantic coast of Florida and the Caribbean.
“It was surprising to consistently see earlier arrivals when we independently assessed satellite data and conventional ground-based observations of intense tropical cyclones,” said Chu.
Warmer oceanic conditions driven by climate change
The team looked at Hurricane Harvey, a Category 4 hurricane that made landfall on Texas and Louisiana in 2017. The hurricane inflicted catastrophic flooding, resulting in more than 100 deaths.
The researchers used simulations from multiple global climate models and found that warmer oceanic conditions developed earlier. These conditions favour the earlier onset of intense tropical cyclones.
The warming was mainly caused by greenhouse gas emissions, the team found.
“In a future with high carbon dioxide emissions, the earlier shifting trend is projected to be amplified,” said Chu.
In South China and the Gulf of Mexico, the earlier onset of intense tropical cyclones contributes to an earlier onset of extreme rainfall.
Understanding changes in hurricane activity is vital for disaster prevention
“Given the seasonal advance of intense tropical cyclones, as shown in this study, the potential for simultaneous occurrence with other high-impact weather events should be a serious concern for the society,” concluded Chu.
“Understanding potential changes in hurricane activity in response to global warming is important for disaster prevention, resource management and community preparedness.”
