hinted at in previous section, we call these near-term models _climate conditioned_ . It is necessary to use such general terminology because there is disagreement among scientists about the ultimate causes of elevated hurricane activity in climate conditioned catastrophe models (CC catastrophe models). More specifically, there is disagreement among scientists about the significance of the observed approximate 0.5<sup>o</sup> C rise in SST over the last 30 years. One group of scientists believes that this rise in SST is part of a multidecadal cycle that is signaled by variations in de-trended SST records<sup>21</sup> . Another group of scientists believes that this rise in SST directly drives increases in hurricane activity<sup>22,23</sup> . Since the IPCC has concluded that SST has risen approximately 0.5<sup>o</sup> C over the last 30 to 50 years<sup>24</sup> , we might take CC models to reflect the maximum potential increase in hurricane activity that might occur from the last 30 to 50 years’ worth of climate change (CC)<sup>25</sup> .

In the case of two out of the three major catastrophe modeling firms, both non-climate conditioned and climate conditioned models are available, which allows for a convenient non-CC versus CC study to be made26. We already laid the groundwork for this comparative study by giving the LECs _BN_ and _CC_ at the end of the previous section above. In the following section, we present a simple method for comparing these two different LECs and show how this method is a useful way to understand the differences among LECs in general.

21 Goldenberg, S. B., Landsea, C. W., Mestas-Nunez, A. M., and W.M. Gray (2001): “The Recent Increase in Atlantic Hurricane Activity: Causes and Implications,” _Science_ , 293, pp. 474-479. http://www.sciencemag.org/cgi/reprint/293/5529/474.pdf

> 22 Emanuel, K. (2005): “Increasing destructiveness of tropical cyclones over the past 30 years,” _Nature_ , 436, pp. 686-688.

http://www.nature.com/nature/journal/v436/n7051/pdf/nature03906.pdf 23 Webster, P. J., Holland, G. J. , Curry, J. A., and H.-R. Chang (2005): “Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment,” _Science_ , 309, pp. 1844-1846. http://www.sciencemag.org/cgi/reprint/309/5742/1844.pdf 24 IPCC (2007): “Summary for Policymakers. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change,” Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (editors), Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-spm.pdf 25 In this report, depending on the context, CC stands for both climate conditioned and climate change. The apparent double meaning is tolerable as the underlying intention is the same. Climate change, according to the IPCC’s usage (see footnote 1 in [6]), refers to any change in climate over time, whether due to human activity or natural variability. Climate conditioned here means essentially the same thing: CC catastrophe models only gauge potential increase in hurricane activity correlated with past increases or variations in SST. Whether these SST increases or variations are ultimately driven by human-driven changes in SST or natural variability is not decided by CC catastrophe models 26 Karen Clark & Company (2008).

9