Carbon Dioxide and Earth's Future Pursuing the ... - Magazooms

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As a result of these findings, the two researchers concluded that “if there is an increase in
hurricane activity connected to a greenhouse gas induced global warming, it is currently
obscured by the 60-year quasi-periodic cycle.” Consequently, and in spite of the fact that (1)
the hurricane record they analyzed started during the final stages of the Little Ice Age (which
was the coldest period of the current interglacial), and that (2) the planet experienced a
subsequent warming that has been declared by climate alarmists to have been unprecedented
over the past millennium or more, they could still find no convincing real-world evidence that
global warming enhances either the frequency or intensity of hurricanes occurring over the
Atlantic Ocean.
Contemporaneously, Klotzbach and Gray (2008) employed sea surface temperature (SST) data
for the far North Atlantic (50-60°N, 50-10°W) and sea level pressure (SLP) data for the North
Atlantic (0-50°N, 70-10°W) to construct an index of the Atlantic Multidecadal Oscillation (AMO),
which they defined as the difference between the standardized SST and SLP anomalies (SST-
SLP) for the hurricane season of June-November, and which they evaluated for the period 1878-
2006, after which they compared their results (to which they applied a 1-2-3-2-1 filter) with a
number of hurricane or tropical cyclone (TC) properties. And this work revealed the existence
of three positive and two negative AMO phases over the period of their study, as may be seen
in the figure below.
North Atlantic AMO Index. Adapted from Klotzbach and Gray (2008).
In comparing annually-averaged results for TC characteristics between the positive and
negative AMO phases indicated in the above graph, it can be calculated from the TC data of the
two researchers that the positive AMO phase-to-negative AMO phase ratios of hurricane
numbers, hurricane days, major hurricane numbers and major hurricane days were 1.53, 1.89,
2.00 and 2.46, respectively, over the entire period studied, while for the 20 most positive and
20 most negative AMO years the values of the same ratios, in the same order, were 1.73, 2.41,
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