Kerry Emanuel

Nature Communications

Published date December 2, 2021

Atlantic tropical cyclones downscaled from climate reanalyses show increasing activity over past 150 years

Study key findings & significance

  • Climate modeling shows that North Atlantic hurricanes have increased in frequency over the last 150 years, similar to what historical records have shown.
  • In recent years, scientists have questioned whether the observed upward trend in Atlantic hurricane frequency is a reflection of reality, or simply an artifact of lopsided record-keeping.
  • The study also found that the frequency of tropical cyclones globally has not changed significantly in the last 150 years.

Author quotes

“The evidence does point, as the original historical record did, to long-term increases in North Atlantic hurricane activity, but no significant changes in global hurricane activity. It certainly will change the interpretation of climate’s effects on hurricanes — that it’s really the regionality of the climate, and that something happened to the North Atlantic that’s different from the rest of the globe. It may have been caused by global warming, which is not necessarily globally uniform.”

“There’s been this quite large increase in activity in the Atlantic since the mid-19th century, which I didn’t expect to see."

“The general trend over the last 150 years was increasing storm activity, interrupted by the hurricane drought [a period during the 1970s and 80s when the number of yearly hurricanes momentarily dropped]. And at this point, we’re more confident of why there was a hurricane drought than why there is an ongoing, long-term increase in activity that began in the 19th century. That is still a mystery, and it bears on the question of how global warming might affect future Atlantic hurricanes.”

Kerry Emanuel, the Cecil and Ida Green Professor of Atmospheric Science in MIT’s Department of Earth, Atmospheric, and Planetary Sciences


Abstract

Historical records of Atlantic hurricane activity, extending back to 1851, show increasing activity over time, but much or all of this trend has been attributed to lack of observations in the early portion of the record. Here we use a tropical cyclone downscaling model driven by three global climate analyses that are based mostly on sea surface temperature and surface pressure data. The results support earlier statistically-based inferences that storms were undercounted in the 19th century, but in contrast to earlier work, show increasing tropical cyclone activity through the period, interrupted by a prominent hurricane drought in the 1970s and 80 s that we attribute to anthropogenic aerosols. In agreement with earlier work, we show that most of the variability of North Atlantic tropical cyclone activity over the last century was directly related to regional rather than global climate change. Most metrics of tropical cyclones downscaled over all the tropics show weak and/or insignificant trends over the last century, illustrating the special nature of North Atlantic tropical cyclone climatology.