To more broadly inform the US public about the upcoming hurricane season, the Project on Climate Science this morning arranged a national radio satellite tour with Greg Holland, a hurricane expert with the National Center for Atmospheric Research and director of its Earth System Laboratory. Some of the shows were live, some were taped, but I was allowed to listen in on both.

The experience was very revealing, and provided a lot of perspective on the upcoming season. Some highlights:

The Atmospheric/Ocean Conditions: Holland explained that this year is shaping up a lot like 2005, the worst year on record. On a Westchester, New York show, he commented that “unfortunately, the conditions that are out there at present are very similar to what we observed in the lead up to Katrina.” In particular, Holland pointed to the very warm ocean (with sea surface temperatures at “all time record levels”) and the fact that we’re coming out of an El Nino, which suppresses hurricanes in the Atlantic. The current conditions do the opposite.

“I sure hope the forecasts are wrong, but forecasts are going anything from 14 up to the mid 20s for the number of storms this year,” Holland said.

The Influence of Global Warming: There has been massive debate over just how much hurricanes could change due to the changing climate. Many parameters could be altered, including average storm intensity, average storm numbers, standard storm tracks or regions of occurrence, and so forth.

On a South Carolina show, Holland admitted that when it comes to the frequency of storms, “there’s a lot of debate.” He said that while people like himself think the total numbers will go up, other experts think the opposite.

As far as intensity is concerned, though, Holland asserted that there is “no real debate…if there is warmer sea surface temperatures and all other things are equal, you will get on average more intense cyclones.” And he went further. Down the line due to climate change, Holland argued, he expects “a very substantial, perhaps even a doubling of the category 4 and 5 hurricanes, even if the total number may not change much.”

When it comes to climate impacts on hurricanes, one other factor that we often don’t talk about is precipitation. A warmer atmosphere holds more moisture, and that will surely show up in the hurricane rainfall tally. On the Westchester show, Holland said the current prediction is that hurricanes “will carry about 20 percent more rainfall due to global warming.”

Specific Vulnerabilities: On a radio satellite tour, different regions of course want to know how they in particular could be impacted by hurricanes. It varies, but there are some pretty big specific vulnerabilities.

Take New York City. As Holland told the Westchester show, a big enough storm surge “could completely shut the city down for a long period of time if it got into the subway and knocked out your communications.” This is one of the hurricane worst case scenarios for the U.S. that I detailed in my book Storm World. Every year, the possibility arises again. The odds may be low, but some day, it will really happen.

The Oil Slick. There were questions about what happens when cyclone meets slick, of course. Holland’s view was that it was a good news/bad news situation. He said a storm would actually mix up the slick, breaking it into smaller “globules” that would be more easily consumed by bacteria.

But of course, if a storm headed towards shore across the slick, its storm surge could also “drive some of the oil into the fragile wetlands, where it will be a lot harder to remove it.”

How Does This Affect the Average Citizen? On an Ocean City, Maryland show, Holland was asked what this means for the average person looking ahead to a rough year, or many rough years. He made two points. First, for those living in storm-prone areas, the best idea is to get ready now in case you have to evacuate–and then, if the forecasts turn out to be wrong and we have a calm year, “the worst that’s happened is you’ve cleaned around the house and you’ve got a nice plan together.”

More broadly, Holland said we have to get ready for many years like this one. ”These are the sort of conditions we’re going to have to put up with,” he said. We have to adapt to that. Not pretty, but probably not avoidable, either.