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Monitoring and Understanding Changes in Extremes: Extratropical Storms, Winds, and Waves

Graphic demonstrating the state of knowledge regarding changes in various climate extremes

Authors’ assessment of the state of knowledge regarding 600 changes in various climate extremes. The horizontal axis depicts how useful the data actually are for assessing historical changes. The vertical axis depicts how well the mechanisms driving changes are understood. For each axis, phenomena are assigned to one of three categories of knowledge, and the dashed lines toward the upper right imply that knowledge about the phenomena is not complete. Extremes discussed in previous assessments appear in grey text.

Extreme weather can cause injuries, causalities, and billions of dollars in damages. Since 1980, the United States alone has sustained well over 100 weather and climate disasters where damage exceeded one billion U.S. dollars. Monitoring and understanding changes in these extreme events allows governments, industries, and individuals to better anticipate future natural disasters and decide how to make preparations and alert their constituents and families. In an effort to further understanding of three types of these extremes, scientists examined changes in extreme extratropical storms, winds, and waves in a new scientific assessment—Monitoring and Understanding Changes in Extremes: Extratropical Storms, Winds, and Waves—that will be published in the Bulletin of the American Meteorological Society.

Focusing on U.S. coastal regions during the cold season, November–March, the assessment found that extratropical storms have been occurring more frequently and with greater intensity since 1950. The assessment defines an extratropical storm as “any synoptic-scale low pressure system developing in mid- and high-latitudes.” Essentially, these storms are ones that develop along the boundary of warm and cold air masses outside of the tropics. They account for the majority of weather systems that affect the United States, particularly in winter, such as Nor’easters. Coastal areas are especially at risk to damage from these storms as they accentuate tides and enhance storm surge, effects that are compounded even more and extended inland as sea levels rise.

Extreme winds, which often come along with extratropical storms, are not only damaging but also contribute to other extremes, such as extreme waves and storm surge. While evidence does not currently show any trends in extreme winds over land, they have been on the rise over parts of the ocean for the last decade or two. On the other hand, evidence does suggest that extreme waves have been increasing, particularly during the winter months along the U.S. Pacific coast since the 1950s.

Overall, scientists’ ability to measure changes in extratropical storms, winds, and waves is relatively new. But like the climate system itself, the state of knowledge on extremes is continuing to evolve. As scientists further study these extreme events, our understanding of not only their changes but also the causes of their changes will continue to improve.

See the online release of Monitoring and Understanding Changes in Extremes: Extratropical Storms, Winds, and Waves from the Bulletin of the American Meteorological Society to read the full report.