making things needlessly too complicated.  A much better approach is to take the position that polluting the air is highly immoral.  If we stopped industrial air pollution and air pollution caused by human overpopulation (i.e., making fires wouldn't cause a problem if there were far fewer humans and they lived where it's warm), issues like unnatural global warming would take care of themselves.  Always go to the root of the problem for an effective solution!

Roberts makes some accurate individual points, but he's missing the storm for the raindrops.  No, we shouldn't undermine credibility by claiming that Katrina or any other specific hurricane was a direct consequence of global warming.  But we should be SHOUTING from the ROOFTOPS (not fudging and agonizing over details) that Katrina and other storms ILLUSTRATE the world that we're creating through climate change.

There is strong science behind this claim.  Furthermore, it is intuitive and easy for the non-scientific public to understand.  Flames under a pot of water make it boil.  Heating up sea surface temperatures increases evaporation and storms.

There is also strong science behind the fact that people make decisions irrationally, and respond more to visually dramatic events than to more dangerous, but less concentrated or dramatic ones.  It follows that big storms are likely to be the NUMBER ONE WAY to communicate the dangers of climate change to the public.  But I see green groups asleep at the wheel on this one.  (At least I haven't heard a peep through the mainstream media.)

Any person or organization serious about mobilizing political will to slow global warming should be throwing tons of energy into the storms-warming argument RIGHT NOW.  The timing is right, in the wake of Katrina and last year's big hurricanes.  And it honors the victims to work on reducing the severity of future storm tragedies.

I'll close by reiterating that while the messaging is a bit subtle and requires some care, it's not hard.  No, we can't say Katrina was due to warming (though her severity well might have been).  But we can say out loud she illustrates warming's danger.  

Suppose you wanted to warn people of the threat posed by a new and powerful kind of bomb, in the hope of preventing its first use.  An asteroid strikes the earth, causing an explosion of the same magnitude as would be generated by the bomb.

Would you use the asteroid damage to communicate what the bomb is capable of?  Or would you shy away, worried that this would be unscientific?  After all, the only way really to know the capability of the bomb would be to try one out.  Is that what the public deserves?

Should greens use hurricanes to promote awareness of global warming? Even though there is no clear direct evidence that one has something to do with another? Yes!
On the science issue; Hurricanes are huge heat-pumps. They remove the heat from the surface of equatorial oceans in the form of water vapor, and dissipate it into the upper atmosphere, where the vapor looses its heat and condenses and falls as rain. (That is the basic principle of refrigeration.) While it is true that more than warm surface ocean water is needed, lack of wind shear in the upper atmosphere must also exist, the warmer the water, the more severe the hurricane will be when it does form. Look what happened to Katrina when it hit the warmer water of the Gulf of Mexico. It grew from a nuisance to a monster because of a few degrees upward difference in surface water temperature.
The question is not whether hurricane frequency/severity is connected to global warming, the question is how much more proof do you want? How much more proof can the people of the southern Atlantic coast, the Caribean, and the Gulf coast survive?

RVA

Hurricanes gain strength as they pass over warm waters.  One news item pre landfall, was that the waters were 90 degree F, certainly warmer than in past years.  Global warming causes increased temperatures of both water and land areas.  Because there are no 100% credible explanations for climatic events, there can be no actions justified if the threshold iks 100%.  However, to deal with this enigma, it is useful to employ the Precautionary Principle, which, in essence, states: "When an action has the potential to cause significant harm to humans or to the environment, it is not necessary to have 100% proof to justify preventive or mitigating actions."
Bottom line: Global warming should be considered a significant contributor to Katrina and future hurricanes.

Julian

The difficulty in this discussion (in my opinion) is that nature lovers and environmentalists are forced to prove their case with science.  We go to war based on conjecture, but a comprehensive, peer-reviewed study about the human factor in climate destruction doesn't merit even recognition of a problem?

Linking Katrina to global warming--albeit accurate--would only add to a flawed practice of discussing the environment in scientific terms. Nature evokes emotion and is more powerful for most people than what's found in a natural science textbook, presumably even for President Bush.  Facts and education aren't working because it's easy to disregard the things that don't affect you emotionally or aren't communicated in emotional terms.  Maybe this is a good time to take the environment back from policy makers and scientists, and say: Yes, nature's awesome force caused Katrina and destruction is most regretable.  But what does our environment offer, that, to the same extreme the hurricane was ferocious, is equally intense in beauty, purity and peace?

Maybe dialogue about protecting our environment should be more about emotions and values with science and fact as "rational" support.

Right on, JulchenBuns.  That's basically the point I was trying to make.  Wisdom should always trump intellect.

to me it seems that the language used by researchers --- "we can neither prove" nor "disprove" anything --- has left the door open for industry mouth-piece think tanks and non-science trained journalists to at least misinform the public and at worst mislead the public.  for example when pressed about evolution by the public, scientists, by continuing to abide by the scientific jargon, have had to say that they "can't prove that it happened."  this creates the room for the possibility/legitimacy of psuedo-science such as "intelligent design."  so how about this rule of thumb: when you're in the ivory tower, use the code.  when you're not in the tower, don't use the code.  maybe this way people can understand science and hopefully use it, as the powerful tool it is, to make informed decisions.  who knows, we'd maybe then not be fighting a war for oil knowing that its use is changing our climate.            

As you might hear on NPR this evening in a story about CAFE standards and the new CO2 emissions rules for cars here is one attempt at telling this story and connecting it to real efforts to curb emissions:

The transportation sector is the fastest growing source of greenhouse gas emissions.

Science tell us that greenhouse gas emissions are destabilizing our climate and that this destabilization will lead to more frequent catastrophic events like Katrina.

Seth Kaplan, Senior Attorney Conservation Law Foundation 62 Summer Street Boston MA 02110 (617) 850-1721 (voice)