There’s an interesting Realclimate post discussing whether or not global warming makes tropical cyclones stronger. The basic answers is that we might expect the number of tropical cyclones (TCs) to decrease overall, but see an increase in the frequency and intensity of the strongest ones.As indicated by the figure on the right, there are also suggestions that such increase is actually being observed. For more details, it probably reading the Realclimate post. You could also read Elsner et al. (2008) and Kossins et al. (2013), both of which find an increase in the intensity of the strongest TCs (although the homogenisation method used in the latter does reduce the trend).
However, it seems that there is not complete agreement that we are indeed observing an increase in the frequency and intensity of the strongest TCs. It’s a difficult analysis and the results can vary as the datasets improve. However, ,any who do dispute the existence of any trend, tend to highlight that there are no trends in the accumulated cyclone energy (ACE). This is actually what I was wanting to discuss. I’ve been looking through a paper by Kang and Elsner called Climate Mechanism for Stronger Typhoons in a Warmer World.I’m not entirely sure that I quite get it, but I think a key point is demonstrated by the figure on the left. It shows a correlation screen of global ocean warmth (global mean sea surface temperatures) and climate variability of the top 10% of TCs in the Western North Pacific. INT is essentially intensity, FRQ is frequency, ACT is essentially ACE, and EINT is efficiency of intensity (fewer TCS but stronger).
What (I think) it shows is that increasing sea surface tempertures correlates with a reduction in TCs but an increase in the intensity of the strongest ones. What it does not show is any correlation with ACT, or ACE. As the paper says
Increasing EINT in a warmer year shows that this environment further inhibits the TC occurrences over the region, but TCs that form tend to discharge stored energy to the upper troposphere with stronger intensities. As the increasing intensities compensate for the loss of ACT by decreasing number of TCs, the ACT remains largely unchanged.
So, this paper seems to be again consistent with the general expectation that we would expect the strongest TCs to get stronger as we warm, but that we might expect a reduction in TCs overall. These two factors then tend to compensate in such a way that there is then little change in the accumulated cycle energy (ACE, or ACT). Hence, it would seem that one should be careful of using ACE to infer things about trend in TCs.
The increasing intensity of the strongest tropical cyclones (Elsner et al. 2008).
Trend Analysis with a New Global Record of Tropical Cyclone Intensity (Kossin et al. 2013).
Climate Mechanism for Stronger Typhoons in a Warmer World (Kang & Elsner 2016).
Does global warming make tropical cyclones stronger? (Realclimate)