Study Finds Hurricanes Frequent in Some Cooler Periods

Over the last 5,000 years, the eastern Caribbean has experienced several periods, lasting centuries, in which strong hurricanes occurred frequently even though ocean temperatures were cooler than those measured today, according to a new study.

The authors, from the Woods Hole Oceanographic Institution, say their findings do not necessarily conflict with recent papers asserting a link between the region’s hurricane activity and human-caused warming of the climate and seas.

But, they say, their work does imply that factors other than ocean temperature, at least for thousands of years, appear to have played a pivotal role in shaping storminess in the region.

The study compared a 5,000-year record of strong storms etched in lagoon mud on the Puerto Rican island of Vieques with data on ocean temperatures and climate and storm patterns. The analysis is being published today in the journal Nature.

The Woods Hole team found that stormier spans, including one from 1700 until now, were associated with a relative paucity of El Niño warm-ups of the tropical Pacific Ocean and also with periods of heightened monsoon intensity in West Africa.

El Niño episodes tend to change wind patterns in ways that weaken Atlantic Ocean hurricanes, and Africa is a nursery for storm fronts that can drift westward and develop into hurricanes.

Storm records extracted from sediments on the Gulf Coast by other scientists, and near New York City by the Woods Hole team, show a similar pattern, implying that the shifts from quieter to stormier times are not just a local phenomenon, the authors said.

Jeffrey P. Donnelly, the lead author, said the findings pointed to the importance of figuring out an unresolved puzzle: whether global warming will affect the Niño cycle one way or the other. More intense or longer Pacific warm-ups could stifle...

Is this true believer now a heretic?

J. Donnelly
On the Puerto Rican island of Vieques, members of the Woods Hole research team collected sediments left by hurricanes of earlier times.
Paleotempestology Resource Center

Intense hurricane activity over the past 5,000 years controlled by El Niño and the West African monsoon

The processes that control the formation, intensity and track of hurricanes are poorly understood1. It has been proposed that an increase in sea surface temperatures caused by anthropogenic climate change has led to an increase in the frequency of intense tropical cyclones2, 3, but this proposal has been challenged on the basis that the instrumental record is too short and unreliable to reveal trends in intense tropical cyclone activity4. Storm-induced deposits preserved in the sediments of coastal lagoons offer the opportunity to study the links between climatic conditions and hurricane activity on longer timescales, because they provide centennial- to millennial-scale records of past hurricane landfalls5, 6, 7, 8. Here we present a record of intense hurricane activity in the western North Atlantic Ocean over the past 5,000 years based on sediment cores from a Caribbean lagoon that contain coarse-grained deposits associated with intense hurricane landfalls. The record indicates that the frequency of intense hurricane landfalls has varied on centennial to millennial scales over this interval. Comparison of the sediment record with palaeo-climate records indicates that this variability was probably modulated by atmospheric dynamics associated with variations in the El Niño/Southern Oscillation and the strength of the West African monsoon, and suggests that sea surface temperatures as high as at present are not necessary to support intervals of frequent intense hurricanes. To accurately predict changes in intense hurricane activity, it is therefore important to understand how the El Niño/Southern Oscillation and the West African monsoon will respond to future climate change.

Judith A. Curry, an atmospheric scientist at Georgia Tech, said the new study, together with other recent research on warming and storms by her and others, added to a picture of rising risk and lagging government action on reducing vulnerability of coastal populations in the Atlantic and Caribbean hurricane zone.

Notice the propaganda ploy here (well, one of many - this is the NYT, after all) - they quote comments by an "atmospheric scientist", commenting not on the science, but rather in support of a clearly political agenda...

so, the table is now set..

climate change causes more hurricanes when it’s hot out

climate change causes more hurricanes when it’s cool out

how they can talk through both sides of their mouths without tripping up their tongue is beyond me..

But, they say, their work does imply that factors other than ocean temperature, at least for thousands of years, appear to have played a pivotal role in shaping storminess in the region.

It has been clear for some time that atmospheric stability is a major factor. Hurricanes need a temperature differential, but they need a large nearly stable area to develop in. Larger hurricanes mean more existing stability much more than they mean more overall heat.

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