Evaluating Tropical Cyclone Exposure & Vulnerability

Over the past few decades, the locations where tropical cyclones reach their maximum intensity have been shifting toward the poles. For the western North Pacific Ocean in particular, this shift has also affected the region’s exposure to the impacts of tropical cyclones, according to a new paper published in the Journal of Climate titled “Past and Projected Changes in Western North Pacific Tropical Cyclone Exposure.” An examination of future climate conditions with computer-generated simulations also led the scientists to conclude that these trends are likely to continue.

In the region of the Philippine and South China Seas—including the Marianas and Philippines, Vietnam, and Southern China—exposure to tropical cyclones between 1980 and 2013 has decreased. So, these areas are less susceptible to impacts of these intense storms. However, in the region of the East China Sea—including Japan and the Ryukyu Islands, Korea, and parts of eastern China—exposure to tropical cyclones has increased, making these areas more susceptible to their impacts.

In some regions, the scientists saw the exposure to tropical cyclones cut in half or more. While in other regions, the scientists saw the exposure double or more. They attributed these changes to not only the shift of tropical cyclones toward the poles but also to an overall basin-wide decrease in the occurrence of these storms.

“In some regions, these two factors have had a compounding effect, with tropical cyclone tracks shifting away from them, while overall the storms are also occurring less often,” said Jim Kossin, the paper’s lead author, who is an NCEI scientist currently stationed at the NOAA Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin–Madison. “In other areas,” he continued, “the tracks have shifted toward them, counteracting the overall decrease in storm number.”

While the full effects of these changes may vary from region to region, they can have vast consequences. In some areas where tropical cyclones have occurred regularly in the past, people depend on these storms to replenish their freshwater supplies. Even though fewer storms can reduce risks of injury and death, the people in these regions have already become resilient to their impacts over the years. Consequently, the long-term threats of these changes are likely to outweigh the potential benefits.

In areas where tropical cyclones haven’t occurred regularly—or at all—in the past, people are unlikely to be prepared for their impacts. So, the effects on infrastructure, property, and lives could be even more devastating.

When looking into the causes of these changes, the scientists could not attribute them entirely to natural climate patterns in the region. “This provides evidence that human-caused climate change is influencing these changes in tropical cyclones,” Kossin said, “It is imperative that we continue examining how and why tropical cyclones are changing so decision makers around the world can help communities better prepare for the future.”