The interpretation and implications of the Knutsonet al. 2020 projections of changes in the frequency and intensity of tropical cyclones under climate change

Abstract

A recent meta-study presented distributions of the possible impacts of climate change on the frequency and intensity of tropical cyclones for the six main tropical cyclone basins, summarizing many previous studies. However, it is not obvious how to interpret the distributions given in the meta-study. I describe algorithms that can be used to interpret the changes in frequency and intensity in a mutually consistent way. I then investigate the nature of the relationships between the changes in frequency and intensity and find that the intensity changes are just a different way of looking at the information provided by the changes in frequency. The mean of the mean intensity distribution increases in all basins. In some basins this increase is associated mostly with an increasing frequency of the most intense tropical cyclones, while in other basins it is associated mostly with a decreasing frequency of less intense tropical cyclones. I consider the implications for a simple measure of risk that combines changes in frequency and intensity, and find that the most extreme risks increase for five out of six of the basins using this measure. The results of this study can be used to produce mutually consistent simulations of changes in tropical cyclone frequency and intensity. These can be used for further analysis of the effects of climate change on tropical cyclones. However, the results come with the major caveat that there are many uncertainties in the inputs and in the various steps of analysis. Finally, I give recommendations for which metrics could usefully be extracted from climate models in future studies of tropical cyclones under climate change to help with interpretation and impacts studies.

Tropical Cyclones and Climate Change: Global Landfall Frequency Projections Derived from Knutson et al.

“…I have investigated how these issues can be resolved in a recent series of research projects (Jewson (2021a), Jewson (2022a) and Jewson (2022b)). In this article I apply the learnings from this research, along with a new methodology for relating lifetime maximum intensity to landfall intensity.…”