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A Five-Decade Analysis of Tropical Cyclone Trends in the South China Sea

19 Aug 2020 | Science Notes

From CO2Science.org: One of the tenets of climate alarmism is the belief that CO2-induced global warming will increase both the frequency and magnitude of extreme weather events, including tropical cyclones or hurricanes. And in this regard, many are so blinded by their faith in model projections of this occurring that nary a hurricane arises without alarmists claiming it has been caused or made worse because of global warming. But is there any truth to such assertions? A simple test to scientifically determine the answer is to examine the historical records to determine if observations either support or invalidate the hypothesis. And in this review, we highlight the results of just such an analysis investigating hurricane trends in the South China Sea.

Paper Reviewed: Bo, X., Xinning, D and Yonghua, L. 2020. Climate change trend and causes of tropical cyclones affecting the South China Sea during the past 50 years. Atmospheric and Oceanic Science Letters doi.org/10.1080/16742834.2020.1752110.

The authors of the study are Bo et al. (2020), three Chinese researchers who utilized two tropical cyclone databases, one from the Shanghai Tropical Cyclone Institute of the China Meteorological Administration and the other from the Joint Tropical Cyclone Warning Center of the United States, to study trends in the frequency and magnitude of such extreme weather events occurring in the South China Sea (SCS) over the period 1965-2017. During this time the CO2 concentration rose by approximately 27% and the earth experienced what climate alarmists refer to as unprecedented global warming not seen for over at least the past 1,000 years. So, with the so-called deck stacked in their favor, what did the record show?

Bo et al. identified a total of 535 tropical cyclones affecting the SCS over the five-decade period, which were mainly distributed within the months of June through November. The annual frequency, plotted in Figure 1a, reveals there has been a statistically significant declining trend in these data, with the annual frequency of tropical cyclones declining from an average of 11 per year at the beginning of the record to 9 per year at the end.

With respect to trends in tropical cyclone strength, the scientists utilized a new Cyclone Activity Index (CAI), which they say “includes tropical cyclone intensity and scale as parameters and combines with the tropical cyclone track to quantitatively calculate the comprehensive influence of the tropical cyclone.” The results of the CAI analysis reveal a significant decline as illustrated in Figure 1b, which weakening the authors say “indirectly validates the trend of overall activity reduction and influence decline for the tropical cyclones affecting the SCS, thereby providing a very valuable reference for future TC forecasts of the SCS.”

Hopefully, climate alarmists will take note, recognize that claims of increasing hurricane activity from CO2-induced global warming are not occurring in the SCS. Nor are they occurring elsewhere, as additional studies we have highlighted on our website have reported similar observations for other locations throughout the world’s oceans (see the many reviews we have posted under the topical heading of Hurricanes in our Subject Index).

Figure 1. Annual frequency (panel a, blue line) and Cyclone Activity Index (panel b, green line) of tropical cyclones affecting the South China Sea over the period 1965 to 2017. The black dashed lines are fitted linear trends. The Cyclone Activity Index series is for the region of maximum values for this parameter (15-22°N, 111-120°E) as indicated by the authors in the original text. Adapted from Bo et al. (2020).

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