Alan K. Henderson's Weblog

Hurricane Katrina should be a wake up call for President Bush on the need for urgent US action to tackle climate change, Friends of the Earth said today. The hurricane is one of the worst natural disasters America has ever faced and is a stark reminder of what scientists expect to happen as a result of human induced climate change.

Although there is at present no means by which to tell whether this particular storm was due to human induced global warming, the devastation it has caused is consistent with the projections generated by climate change models that suggest such storms will become more severe as the world warms up.

Computer models projecting the impacts of climate change on the weather suggest that increased sea surface temperatures caused by global warming will lead to more intense hurricanes. Research findings published in the science journal Nature [1] in July suggests that this is already happening. The analysis, by climatologist Professor Kerry Emanuel of the Massachussetts Institute of Technology, says that major storms in the Atlantic and Pacific since the 1970s have increased in intensity by about 50 per cent. This trend is closely linked to rises in the average temperatures of the sea surface

Hurricanes require warm sea surface temperatures (SSTs), and last year the tropical Atlantic sea surface temperatures were running well above normal. Global warming was the explanation given by most 'experts' the media interviewed. And since global warming will only get worse, those SSTs were expected to just keep on increasing.

But now those same regions that had anomalously warm SSTs last year are -- gasp! -- near normal. The accompanying graphic shows large areas in the tropical Atlantic even a little cooler than normal.

This is not the only surprisingly cool SST story. A new scientific article now accepted for publication in Geophysical Research Letters shows that the globally averaged upper ocean cooled dramatically between 2003 and 2005, effectively erasing 20% of the warming that occurred over the previous 48 years!

The rapidity of this observed temperature change is beyond what computerized climate models can explain. This is perplexing for modelers, who tend to believe that their models contain all of the important physics of the problem.