Image via Wikipedia ; unattributed.
The denialists are mocking the idea of anthropogenically forced increase in Atlantic hurricanes, never mind tropical storms in general.
You could in fact plot “landfalling hurricanes in the US” and get a much noisier plot wherein there is a “robust decline“, the idea that this counts as evidence against anthropogenic forcing being quite disingenuously implied.
But my point again is that (Update: perhaps) the system is getting wobblier. Suppose you take the event “over 15 Atlantic
hurricanes named storms” as a matter of interest. These are the darker of the swans. The number of instances is too rare to extract a statistical trend, but that null result does NOT mean that such events aren’t more likely than they used to be. And what of “over 25 Atlantic hurricanes named storms”. We only have a single event. It’s quite recent. But it’s been followed by more or less ordinary seasons, and extraordinarily few US landfalling hurricanes (currently we are in a record three year gap since the last, and counting).
Now, just for the sake of argument, imagine that hurricanes pretty much go away for thirty years, and then suddenly come back in greater force than ever, with year after year competing with 2005 for a few decades. Then imagine they drop down to an unprecedented low, with no Atlantic tropical storms for a long while. Projecting this trend onto CO2 would yield nothing.
Yet it is not out of the range of the plausible, because several features of the atmosphere have to align for a strong tropical storm year, and each of them is subject not only to monotonic forcing but to wobbles as the system gets larger and larger transients. In other words, the entire complex behavior, by hypothesis, might be forced. The absence of a trend is not enough to say that it is not anthropogenic climate change.
Admittedly, this gets us in the quandary of what evidence to accept as supportive and what to reject. Certainly, explicitly predicted outcomes provide stronger support for the details of the science than complete surprises. Some people are still stuck in hypothesis testing mode, which I think is starting to get a little bit crazy. We can only test hypotheses that way. We cannot use that approach to establish that changing the radiative properties of the atmosphere is safe.
My claim is that we need to get our thinking out of nudge-world. This is not a “nudge”:
(A bit out of date; please mentally extend the green line about to about 394 for today, and probably no less than 500 by the time we are done; perhaps more. I believe the chart is from Hansen’s group but I found it here, courtesy of an oil company btw.)
I don’t understand why people don’t anticipate some ringing in a system that gets kicked this hard.
Update: A real meteorologist speaks on the subject. Less systems theory and philosophical handwaving, more details. Scary enough, but I still see signs of nudge-world thinking.