Here's a thought: my understanding is that
TC frequency is thought to have not changed, and ACE seems to not have changed in recent decades, although variable, if it were in fact true that they had become stronger, they must be more short - lived.
Seems to me the debate about AGHG global warming and increasing
TC frequency / intensity / duration boils down to the fact that as sea surface temperatures, as well as deeper water temperatures rise, the wallop of any TC over warmer seas without mitigating circumstances like wind sheer and dry air off land masses entrained in the cyclone will likely be much more devastating.
There is little evidence of a trend in
the TC frequency, however there are some indications of a trend in the destructive capability of the TCs.
The fact that the RCM - based downscaling approach can reproduce the observed changes when fed modern reanalysis data is used by Knutson et al as a «validation» of the modeling approach (in a very rough sense of the word — there is in fact a non-trivial 40 % discrepancy in the modeled and observed trends in
TC frequency).
So we know that (i) the warming is likely in large part anthropogenic, and (ii) that the recent increases in
TC frequency are related to that warming.
What about their conclusions about a projected decrease in Atlantic
TC frequency, which are, after all, the central point of the paper?
Alternatively, the owners in these «busier» homes (with several dogs or children) may not have had sufficient time to observe the dogs» behaviour, causing a bias in
the TC frequency.
Nor was there any difference between the males and females in
TC frequency when only severe cases where included.
However, climate model studies differ in their account on the tends in
TC frequencies.
Not exact matches
Confidence in the latter is not related to
TC intensity or
frequency; it comes from the probable increase in heavy rain events and the inevitable rise in sea level that will make it easier for storm surges to go inland.
[W] e know that (i) the warming is likely in large part anthropogenic, and (ii) that the recent increases in
TC [tropical cyclone]
frequency are related to that warming.
As pointed out in the post, increasing sea surface temps due to GW is a necessary, if not a sufficient cause for increased
TC intensity and
frequency.
The idea that climate change might actually decrease the
frequency of tropical cyclones (
TCs) is not an entirely new idea.
When discussing the influence of anthropogenic global warming on hurricane or tropical cyclone (
TC)
frequency and intensity (see e.g. here, here, and here), it is important to examine observed past trends.
But, in fact, Emanuel acknowedged the lack of a trend in the
frequency of the
TCs, but finds a trend in their their destructive power which is related to their intensity and duration.
As Morita and Watanabe (2005) reported, the «best track» data shows decrease of the
frequency of strong
TCs in the 1990s in the area 15 - 30 N, 120 - 150 E. (Morita refers to a data set compiled by Japan Meteorological Agency.
Then the media report there's a controvery re, say, the
frequency or intensity of
TC associated with GW, and the viewers think GW has been disproved once and for all.
water temperatures and with an increasing
frequency / severity of
TCs, and you're headed for trouble.
Since daily ACE represents a 4 - times daily sum of wind speed squared, an «average» September 21st could see one of the following (among other combos): One
TC at 125 knots Two
TCs at 90 knots Three
TCs at 70 knots or Six
TCs at 50 knots Current
TCs = 0 September 15: Global Hurricane
Frequency [storms with maximum intensity greater than 64 knots] has dramatically collapsed during the past 2 - 3 years.
The changes in TCHW
frequency and intensity were associated with variations in the number of influencing
TCs (ITC: a
TC that causes at least one TCHW event), ITCTs (ITC time: an observation time with ITCs), the range of ITC influence, and ITC intensity and track.
If
TC intensity or
frequency were able to be shown to be dependent on climate changes (GW), then the argument for mitigation, in the USA at least, would be much strengthened.
All I get from this is that the
frequency of
TC will decrease, but the intensity will increase, and that there is no apparent relation to AGW.
Therefore, our long - period analysis does not support claims that increasing
TC [tropical cyclone] landfall
frequency or landfall intensity has contributed to concomitantly increasing economic losses.
And «most of all,» as they continue, they say that (6) «what is needed is a better theoretical understanding of what sets the
frequency of
TCs,» noting that (7) «we could make much more confident climate change projections if we had a firmer theoretical expectation of what should happen.»
There are a lot of open questions regarding how the
frequency of tropical cyclones (
TCs) is controlled.