Natural Cycles or Global Warming

There seems to be much debate over whether or not the recent increase in the number and severity of hurricanes is due to do global warming. This article from the BBC suggests that it is really to early to tell. But it seems to lean more toward the Natural Cycle theory of current hurricane behavior:

The changing phases of Atlantic hurricane activity are not completely understood; but there appears to be a link to fluctuations in the thermohaline circulation, the global pattern of ocean currents which in western Europe appears as the Gulf Stream.

By causing the sea-surface temperature in the tropical Atlantic to change by even a degree Celsius, these fluctuations can bring major differences to the number of hurricanes generated in a particular year.

They do go on to point out however:

it is difficult to avoid the conclusion that we would all benefit from people on both wings of the issue looking rather more to research. . .

I certainly can't argue with that statement.


This article at RealClimate presents the argument in more the way that I view the situation:

Yet this is not the right way to frame the question. As we have also pointed out in previous posts, we can indeed draw some important conclusions about the links between hurricane activity and global warming in a statistical sense. The situation is analogous to rolling loaded dice: one could, if one was so inclined, construct a set of dice where sixes occur twice as often as normal. But if you were to roll a six using these dice, you could not blame it specifically on the fact that the dice had been loaded. Half of the sixes would have occurred anyway, even with normal dice. Loading the dice simply doubled the odds. In the same manner, while we cannot draw firm conclusions about one single hurricane, we can draw some conclusions about hurricanes more generally. In particular, the available scientific evidence indicates that it is likely that global warming will make - and possibly already is making - those hurricanes that form more destructive than they otherwise would have been.

It would seem that even if the "natural cycle" people are right and this increase in frequency and severity is due to normal cycle of warmer Atlantic Ocean tempertures, it would seem that global warming could only serve to magnify that effect. Even if it is not affecting us yet, do we really want to contribute to the possiblity of future hurricanes like Katrina for our children or grandchildren to deal with?