AGW will make hurricanes worse! No it won't! Yes it will! Maybe.

Al Gore used the Katrina disaster to popularize the notion that global warming would make such monsters a routine occurrence. That notion had no scientific merit, but no matter: Gore had successfully injected it into the public discourse, and it took on a life of its own (for example, it was cited by one insurance company as justification for a rate increase request in Florida).

Today Science Daily brings us another exercise in speculative alarmism related to hurricanes (emphasis added):

The Earth's jet streams, the high-altitude bands of fast winds that strongly influence the paths of storms and other weather systems, are shifting--possibly in response to global warming. Scientists at the Carnegie Institution determined that over a 23-year span from 1979 to 2001 the jet streams in both hemispheres have risen in altitude and shifted toward the poles. The jet stream in the northern hemisphere has also weakened. These changes fit the predictions of global warming models and have implications for the frequency and intensity of future storms, including hurricanes.

Cristina Archer and Ken Caldeira of the Carnegie Institution's Department of Global Ecology tracked changes in the average position and strength of jet streams using records compiled by the European Centre for Medium-Range Weather Forecasts, the National Centers for Environmental Protection, and the National Center for Atmospheric Research. The data included outputs from weather prediction models, conventional observations from weather balloons and surface instruments, and remote observations from satellites.

So, how far has the average position of the jet stream shifted over that 23 year span? About 25 miles. That's nothing -- we're talking about the distance from one side of a large metropolitan area to the other -- but the researchers (and/or whoever wrote the press release) do their best to make it sound frightening.

Storm paths in North America are likely to shift northward as a result of the jet stream changes. Hurricanes, whose development tends to be inhibited by jet streams, may become more powerful and more frequent as the jet streams move away from the sub-tropical zones where hurricanes are born.

Here's the equation: Small shift poleward in the average position of the jet stream = more powerful and more frequent hurricanes. Al Gore, call your movie agent.

So, you're still not impressed with the 25-mile shift? Well, the author of the press release doesn't want us to rest easy:

The poleward shift in their average location discovered by the researchers is small, about 19 kilometers (12 miles) per decade in the northern hemisphere, but if the trend continues the impact could be significant. "The jet streams are the driving factor for weather in half of the globe," says Archer. "So, as you can imagine, changes in the jets have the potential to affect large populations and major climate systems."

Some questions for our researchers:

• Will the trend continue? How do you know?
  
• What was the trend before 1979?
  
• How long is the current trend likely to continue?
  
• How far poleward is the jet likely to go?
  
• Are there any natural mechanisms that will limit or halt the poleward march?

Oh, and is this tiny shift the result of global warming?

"At this point we can't say for sure that this is the result of global warming, but I think it is," says Caldeira. "I would bet that the trend in the jet streams' positions will continue. It is something I'd put my money on."

Whatever you may think about this speculation, let's be clear: it's speculation, not science. The study was about the shift in the jet stream, not about the mechanisms of hurricane development. Of course, that doesn't matter. Some scientists said it, and it fits the AGW template, so it will be reported.