At the Washington Post, Jason Samenow reports on a new study that links reductions in sulfur dioxide emissions to increased hurricane activity:

For hurricanes, heat is fuel.  And if you rob them of this fuel, all other things being equal, they do not grow as intense. Hurricane activity was depressed from the 1960s to 1980s, when both the concentrations of these sulfate aerosols in the U.S. were highest and sea surface temperatures were relatively low.

But from the late 1980s onwards, when clean air legislation began to cleanse the atmosphere of these sun-blocking particles, temperatures and hurricane activity shot up in the tropical Atlantic.

In effect, by ridding the atmosphere of sulfate aerosols, the Clean Air Act may have primed the atmosphere and ocean in the tropical Atlantic for more/stronger storms, especially as greenhouse gas concentrations were rising which added even more heat to the system.

Now as it turns out, the connection between warmer surface temperatures and increased hurricane activity is not as strong as Mr. Samenow makes out, at least for the time being. As Thomas Knutson of NOAA noted recently, while there is a correlation between storm activity and sea surface temperatures, you can also find similarly strong correlations between storm activity and a number of other variables. In fact, when looking over a longer time horizon, “the rising trend in Atlantic tropical storm counts is almost entirely due to increases in short-duration (<2 day) storms alone [which were] particularly likely to have been overlooked in the earlier parts of the record, as they would have had less opportunity for chance encounters with ship traffic.” For this reason, “the historical Atlantic hurricane record does not provide compelling evidence for a substantial greenhouse warming induced long-term increase.” 

But suppose for a moment that there is a real connection between decreased aerosol emissions and more damaging hurricanes. The Obama Administration is beginning to include potential climate change impacts as part of the cost-benefit analysis it conducts on a wide variety of proposed regulations. By the same logic, shouldn’t the cost of not emitting cooling aerosols count against proposed regulations to further reduce SO2 emissions? In fact, it emitting sulfates has the potential to prevent catastrophic global warming, then shouldn’t we be emitting more of them