Nov
28
2006

Mild hurricane season clouds climate picture


Here comes the story of the hurricane: (Photo courtesy NOAA)

The hurricane season ends on Thursday, and by all accounts it was fairly mild. There were nine storms in total, only five of which were strong enough to be labeled hurricanes. This is one-third the number seen in 2005.

The extremely strong season last year led many experts to predict another bad year in 2006. Some claimed the increase would be caused by global warming. Yet Mother Nature refused to cooperate, producing only half the predicted number of storms, causing the experts to continually revise their projections downward.

This highlights the difficulty of making long-term weather predictions, and should give pause to people eager to link every climate phenomenon to a simple cause.

There is no doubt that global temperatures rose from 1980 to 1998 – yet during that time, hurricanes levels were below average. Since 1998, temperatures have stayed at or near their record-high levels. And while there has been more activity of late, only one of those years was strong enough to suggest a global warming link.

Many climate scientists argue that hurricanes run in cycles – a decade or so with lots of storms, followed by a couple decades of much lower activity. They claim recent increase in storms has less to do with climate change and more to do with this natural process.

All of which shows that more research is needed, and it’s best not to make claims – or policy decisions – based on limited data. One strong hurricane season in 2005 does not “prove” global warming, any more than one weak season in 2006 refutes it.

Science Buzz has discussed the hurricane–global warming link in the past, particularly here, here, and here.

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Rebecca's picture
Rebecca says:

I agree with Gene on a lot of his points, particularly "one strong hurricane season in 2005 does not prove global warming, any more than one week season in 2006 refutes it." He strikes a dichotomy that is too often ignored. Global warming advocates continually cite the overwhelming evidence but ignore uncertainties, and critics commit the opposite error. Gene claims that we should proceed cautiously with policy decisions due to these uncertainties, but this is where I disagree.

There is debate among scientists as to whether 2005 reflected an already changed climate or whether it was part of a natural cycle of hurricanes. I would argue that this is irrelevant. In 2005 sea surface temperatures were warmer than average. This is known and wildly accepted to cause more severe storms. Also, this is a predicted consequence of global warming. Whether the warmer sea temperatures were a result of global warming or not, 2005 should be viewed as a glimpse into what could be in our future.

On Nov. 30th, the last day of the 2006 hurricane season, NPR discussed this issue. Their experts, namely Scott Brown from NASA's Goddard Space Flight Center and Greg Jenkins from Howard University, cited three reasons for the mild season.

(1) The average ocean temperature in the tropical Atlantic Ocean was 1-2 degrees warmer in 2005 than 2006. As mentioned above, warmer waters fuel hurricanes allowing them to become more severe and persistent.

(2) Hurricanes develop off Africa's west coast. In 2006, many large systems were formed, but got "squashed" by unfavorable winds. In 2005, the winds were from the east and facilitated the large storms.

(3) Satellite images of the eastern, mid-Atlantic show clouds of dust from Africa throughout August and September 2006. Dust weakens storms. In 2005, satellite photos are clear and free of dust.

Despite cooler ocean temperatures, unfavorable winds and the dust, 5 hurricanes formed over the Atlantic in 2006. Most of these didn't reach the US, and turned off to the north and east. NPR cited a trough of low-pressure air in the northern Atlantic that pulled storms away from the coast. Last year, there was a high-pressure system.

The bottom line is that hurricanes, and any climatic feature, are complex and difficult to understand, much less predict. Still, scientists largely agree global warming is already occurring and should be addressed socially and politically.

posted on Tue, 12/05/2006 - 5:41pm
Anonymous's picture
Anonymous says:

I think hurricane Katrina was very tragic to the people who's friends and family lost their lives

posted on Sat, 12/16/2006 - 4:09pm
Anonymous's picture
Anonymous says:

why didn't we here about thoses hurricanes

posted on Mon, 12/18/2006 - 1:36pm

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