Word: cyclicality
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Bipolar, or manic, depression is characterizedby cyclic fluctations between depressed states andstates of mania, or hyperactivity...
...election vindicates a hypothesis about the cyclic nature of American politics ... Each phase recurs at roughly 30-year intervals. Thus the 1920s, 1950s and 1980s were conservative periods; and thus Theodore Roosevelt brought in the Progressive Era in 1901, Franklin Roosevelt the New Deal in 1933 and John Kennedy the New Frontier in 1961 ... No one, therefore, should be surprised by the arrival of a new liberal phase...
...number of theories have been floated to explain these irregular, rapid variations. The leading one, advanced by Lamont-Doherty's Wallace Broecker and George Denton of the University of Maine, involves a kind of cyclic ocean current that has been likened to a conveyer belt. Broecker and Denton note that a stream of unusually salty (and thus especially dense) water flows underneath the Gulf Stream as it moves from the tropics to the North Atlantic. When this salty stream reaches the far north, it is forced to the surface as water above it is blown aside by the winds...
...production was high and the sun apparently quiescent. But did this mean that all of these periods were times of extreme cold? Many scientists doubted it, suggesting that the correlation between the Maunder minimum and the little ice age might be nothing more than sheer coincidence. Changes in solar cyclic activity, the doubters argued, were not necessarily accompanied by variations in the sun's output of heat and light and probably did not affect terrestrial weather and climate...
...small a cyclic change able to have a noticeable effect on weather? Two scientists suspect it may. Karin Labitzke of Berlin's Free University and NCAR's Van Loon have discovered a relationship between the solar cycle and the stratospheric winds over the tropics. During a 28-month period, these winds reverse direction, blowing half the time from the east, the other half from the west, a phenomenon meteorologists call the QBO, or quasi-biennial oscillation. Depending on the direction of the QBO flow, Labitzke and Van Loon found, solar maximums and minimums seem linked to changes in air pressure...