Is global warming causing stronger hurricanes? Caves may hold the answer.
January 26, 2007
Measuring oxygen isotope variation in stalagmites in Actun Tunichil Muknal cave in central Belize, a team of researchers lead by Amy Benoit Frappier of Boston College have identified evidence of rainfall from 11 tropical cyclones over a 23 year period (1978-2001). The research -- the study of ancient storms is called paleotempestology -- could help create a record of hurricanes that would help researchers understand hurricane frequency and intensity. Currently, reliable history for hurricanes only dates back a generation or so. Prior to that, the official hurricane records kept by the National Oceanic and Atmospheric Administration's Atlantic basin hurricane database (HURDAT) are controversial at best since storm data from more than 20 years ago is not nearly as accurate as current hurricane data due to improvements in tracking technology. The lack of a credible baseline makes it nearly impossible to accurately compare storm frequency and strength over the period.
This image depicts a 3-day average of actual sea surface temperatures (SSTs) for the Caribbean Sea and the Atlantic Ocean, from August 25-27, 2005. Image Credit: NASA/SVS.
"Before aircraft and satellite monitoring were available, the Atlantic hurricane data are likely woefully underestimated - except where a hurricane ran directly over a ship or coastal community and there were meteorological observations of pressures and/or winds recorded," Chris Landsea, a scientist at the NOAA National Hurricane Center, told mongabay.com by email last year. "Given that ship captains did their best to NOT sail into the eye of hurricanes, there is a very large underreporting bias in our databases during the late 19th and early 20th Centuries, except for hurricanes at landfall along populated coastlines."
"What data we do have - and there certainly are biases in HURDAT that need to be addressed storm by storm - suggest that the middle of the 20th Century was about as busy as the last active 11 years have been (1995 to 2005). Disentangling trends due to bias in the hurricane dataset and possible global warming induced changes is then very problematic," he added.
While several studies published since early 2005 have linked recent climate warming to the increasing occurrence and strength of hurricanes over the past thirty years, the research has proved controversial since they relied on potentially flawed data. The new study may help climate researchers re-analyze existing tropical cyclone databases to address these concerns.
"The statistical models presented here open the door to developing highly resolute speleothem records of prehistoric [tropical cyclone] frequency and intensity," write the authors who go on to say that the addition of further cave observation sites outside of Belize could "ultimately contribute to risk assessment and climate change impact detection and/or attribution programs."
Citation: Frappier, A.B. et al. "Stalagmite stable isotope record of recent tropical cyclone events". Geology, February 2007; v. 35; no. 2; p. 111—114; doi: 10.1130/G23145A.
This article is rewritten from a prior mongabay.com article by Rhett A. Butler.