Jim Hansen of NASA made a presentation (5.1 MB download) on February 10 at a conference on Politics and Science in New York City.  In the talk he said:  “NOAA took an official position that global warming was not the cause of hurricane intensification, and as the public was glued to their television listening to reports from the Hurricane Center, that is the main message the public received. The topic is a complex one that the scientific community is working on, but it seems that the public, by fiat, received biased information. NOAA scientists were told not to dispute the Hurricane Center conclusion in public.”

Hansen’s talk at the New School for Social Research—“Can We Still Avoid Dangerous Human-Made Climate Change?”—was very similar to his presentation (5.3 MB download) at the American Geophysical Union meeting in San Francisco on December 6, 2005, given in tribute to Charles David Keeling.  However, his talk at the New School included a slide that he had left out of his December presentation.  The slide (#24) says the following:

“Our climate simulations provided to IPCC, driven by known climate forcings, predominately increasing greenhouse gases, yield a warming of 0.35C in the tropical Atlantic region of hurricane formation in 1995-2005 relative to the preceding 25 years. That is the mean result for a 5-run ensemble. The observed warming in that region was 0.45C.  So the categorical contention that recent hurricane intensification is due to a natural cycle of Atlantic Ocean temperature in the region of hurricane formation, and has nothing to do with global warming, is irrational.  How could a hurricane distinguish between a natural and greenhouse gas warming?  It is not impossible, but it would require an explanation that has not been proffered.  I conclude that greenhouse gases are probably responsible for a substantial fraction of the ocean warming that fuels stronger hurricanes.”

Here is what Hansen’s notes say about the slide:

“I want to mention tropical storms, a topic that I dropped from my AGU talk because of time constraints, because it is especially relevant to this conference. We calculate an ocean surface warming in the region of hurricane formation, caused by human-made climate forcings, that is equal to a large fraction of the observed warming there. So the categorical contention of the NOAA National Hurricane Center that recent hurricane intensification is due to a natural cycle of Atlantic Ocean temperature, and has nothing to do with global warming, is irrational. How could hurricane distinguish between a natural and greenhouse gas warming?  It is conceivable, but it would require an explanation that has not been proffered.  I suggest that greenhouse gases may be responsible for a substantial fraction of the ocean warming that fuels stronger hurricanes.

I mention this because NOAA took an official position that global warming was not the cause of hurricane intensification, and as the public was glued to their television listening to reports from the Hurricane Center, that is the main message the public received. The topic is a complex one that the scientific community is working on, but it seems that the public, by fiat, received biased information. NOAA scientists were told not to dispute the Hurricane Center conclusion in public. I am not certain whether that is legal or not. Perhaps, by declaring the conclusion to be `policy’, NOAA scientists can be prohibited from questioning it in public.”