An international team of researchers has found evidence in tree rings that backs up prior research suggesting tropical cyclones (typhoons in the east, hurricanes in the west) are migrating slowly toward the Earth's poles. In their paper published in the Proceedings of the National Academy of Sciences, the group describes their study of tree ring samples taken from sites in northeastern Asia and what they found.
Prior research has suggested that global warming is causing the tropics to widen, leading to changes in weather patterns. Some evidence has suggested that one such change is likely to be the migration of tropical storms toward the poles. In this new effort, the researchers have found evidence that backs up such suggestions.
The researchers note that little work has been done to investigate the long-term variability of tropical cyclones and their possible impacts on human population centers in the future. Work in this area is necessary, they argue, to expedite mitigation practices in areas likely to be impacted in the future.
To learn more about the history of tropical cyclones in Asia, the researchers collected tree ring samples from sites along the southern coast of South Korea to parts of Russia. Prior research has shown that when cyclones make their way onshore, the impact on surviving trees in the vicinity is reflected in their tree rings. The researchers refer to these events as canopy disturbances. In all, the team looked at ring samples from 54 species of trees that showed evidence of tropical cyclones over the past century. They then compared the rings with records kept of cyclones in the area.
The researchers found evidence of tree damage creeping north starting after the 1920s. They note such a migration is likely to have a major impact on areas that are situated at the edge of past tropical cyclone activity. They suggest people in those areas need to start making mitigation preparations, as they will likely be exposed to such threats in the future.
The work by the team represents the first long-term study of tropical cyclone drift and its possible impact on population centers on the edges of storm activity.
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Jan Altman et al. Poleward migration of the destructive effects of tropical cyclones during the 20th century, Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1808979115