A new peer-reviewed paper has been published in an American Meteorology Society journal that raises many more questions on the linkages between hurricane activity and global warming. Eric Berger at the Houston Chronicle (SciGuy) did the leg-work and is the first
(and only) mainstream media outlet to report the findings of Emanuel et al. (2008) and get reaction from other scientists in the climate/hurricanes community. Andrew Revkin at the Old Gray Lady also has blogged reaction … NY Times DotEarth
Important update: 04/17 MIT press release New MIT study validates hurricane prediction Provides confirmation that climate change intensifies storms
Apparently the above blogs misconstrued, misinterpreted, or just plain flunked this lesson, because the above Press Release has some very different conclusions.
While the earlier study was based entirely on historical records of past hurricanes, showing nearly a doubling in the intensity of Atlantic storms over the last 30 years, the new work is purely theoretical.
“It strongly confirms, independently, the results in the Nature  paper,” Emanuel said. “This is a completely independent analysis and comes up with very consistent results.”
Emanuel does discuss some of the uncertainties, which seem rather important (I think this summarizes about 100% of the contradictory views to North Atlantic + AGW causation):
There are several possibilities, Emanuel says. “The last 25 years’ increase may have little to do with global warming, or the models may have missed something about how nature responds to the increase in carbon dioxide.”
Another possibility is that the recent hurricane increase is related to the fast pace of increase in temperature. The computer models in this study, he explains, show what happens after the atmosphere has stabilized at new, much higher CO2 concentrations. “That’s very different from the process now, when it’s rapidly changing,” he says.
And the final conclusion:
In the many different computer runs with different models and different conditions, “the fact is, the results are all over the place,” Emanuel says. But that doesn’t mean that one can’t learn from them. And there is one conclusion that’s clearly not consistent with these results, he said: “The idea that there is no connection between hurricanes and global warming, that’s not supported,” he says.
…Emanuel employs a downscaling approach to the IPCC model scenarios using synthetic tropical cyclone seedlings to judge the impact of a warming world on future storm activity metrics (frequency, power dissipation). His method’s ability to use historical reanalysis products to fairly accurately reproduce past activity lends credibility to Emanuel’s technique, especially for future activity. Of course there are many caveats concerning model downscaling efforts using IPCC scenarios which have been discussed extensively at CA.
From SciGuy’s blog:
“The results surprised me,” Emanuel said of his work, adding that global warming may still play a role in raising the intensity of hurricanes but what that role is remains far from certain.”
In the new paper, Emanuel and his co-authors project activity nearly two centuries hence, finding an overall drop in the number of hurricanes around the world, while the intensity of storms in some regions does rise. For example, with Atlantic hurricanes, two of the seven model simulations Emanuel ran suggested that the overall intensity of storms would decline. Five models suggested a modest increase.
Dr. Curry from Georgia Tech University also is quoted,
“The issue probably will not be resolved until better computer models are developed…By publishing his new paper, and by the virtue of his high profile, Emanuel could be a catalyst for further agreement in the field of hurricanes and global warming …
Kerry Emanuel has provided a link on his homepage for the BAMS 2008 Article and while a little technical, the paper is a good primer on the current state of the “debate” and presents an even-handed examination of his findings. I encourage all to read it and post their own reviews for consumption by the gallery. Historically, Emanuel’s change in thinking represents one aspect of the evolution of climate science.
***Back in 1987, Time Mag reported upon one of the first articles in Nature to sound the alarm (Emanuel 1987).
a warmer climate could result in hurricanes packing up to 50% more destructive power. This could happen, he suggests, within 40 to 80 years, when some scientists think CO2 levels will have doubled and ocean temperatures will have increased by 2 degrees C to 3 degrees C.
Emanuel (2005) in Nature largely confirmed this hypothesis, almost 20 years later with the so-called climate shift of 1995 (Goldenberg et al. 2001 Science). Back in 1987, the computer technology, climate model development, and physical understanding probably was not there to adequately test the hurricane-warming hypothesis. In 2027, it will be interesting to see what “more work” has been done on the problem…
Flashback to July 31, 2005: Press Release MIT’s presser on Emanuel (2005)