Thursday, February 28, 2013

New paper finds no increase in tropical cyclones over past 200 years

A paper published today in Palaeogeography, Palaeoclimatology, Palaeoecology reconstructs tropical cyclones in Queensland, Australia and finds that "tropical cyclone frequency did not increase in the past 200 years." The paper adds to many other peer-reviewed publications demonstrating that, contrary to the claims of climate alarmists, tropical cyclones have not increased, and in many cases have decreased due to warming, and are projected to further decrease in the future. 

Reconstructing tropical cyclone frequency using hydrogen isotope ratios of sedimentary n-alkanes in northern Queensland, Australia

  • a Department of Earth Sciences, Geochemistry, Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands
  • b Department of Marine Organic Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, The Netherlands
  • c Palaeoecology, Department of Physical Geography, Faculty of Geosciences, Utrecht University, 3584 CD, Utrecht, The Netherlands
  • d Department of Marine Geology, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, The Netherlands
  • e Marine Biogeosciences, Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, Germany


A peat record from Quincan Crater (Queensland, Australia), spanning the past 200 years, was used to test if hydrogen isotope ratios of leaf wax long-chain n-alkanes derived of higher plants can be used to reconstruct past tropical cyclone activity. Queensland is frequently impacted by tropical cyclones, with on average 1–2 hits per year. The most abundant n-alkanes in the peat are C29 and C31. Possible sources for long chain n-alkanes in the peat core are ferns and grasses, which grow directly on the peat layer, and the tropical forest growing on the crater rim. Hydrogen isotope ratios of C27, C29 and C31n-alkanes vary between − 155 and − 185 ‰ (VSMOW), with the largest variability in the upper 30 cm of the record. For the period 1950–2000 AD the variability in δD of C29 alkanes resembles a smoothed record of historical tropical cyclone frequency occurring within a 500 km radius from the site. This suggests that the high number of tropical cyclones occurring in this period strongly impacted the δD signal and on average resulted in more depleted values of precipitation. In the period before 1900 AD, the variability in the hydrogen isotope record is relatively small compared to the period 1950–2000 AD. This might be the result of lower variability of tropical cyclones during this time period. More likely, however, is that it results from the increasing age span per sampled interval resulting in a lower temporal resolution. Average δD values between 1900 and 2000 AD are around − 167‰, which is similar to average values found for the period between 1800 and 1900 AD. This suggests that on average tropical cyclone frequency did not change during the past 200 years. This study demonstrates the potential of stable hydrogen isotope ratios of long chain n-alkanes for the reconstruction of past tropical cyclone frequency.


► δD ratios of long chain sedimentary n-alkanes from a peat core in northern Queensland were analyzed ► δD of the past 50 years resembles the historical record of tropical cyclone frequency in the area ► The results suggest that tropical cyclone frequency did not increase in the past 200 years

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