On average Atlantic tropical cyclones are getting stronger with a trend that is related to an anthropogenic increase in oceanic heat content over the North Atlantic (Emanuel 2005; Webster et al. 2005; Trenberth 2005; Elsner 2007). Consistent with the "heat-engine theory'', increases in tropical cyclone intensity over the past 25 years for the set of strongest storms are noted in other tropical cyclone basins as ocean temperatures rise (Elsner et al. 2008). However, a hurricane's maximum potential energy is inversely related to the temperature above the thunderstorm clouds in the central core (Emanuel 1991; Holland 1997). A warming of the lower stratosphere, near the tropopause (~16 km altitude), resulting from increased UV radiation absorbed by ozone will decrease the convective available potential energy limiting the intensity of the cyclone. Variation in radiation between extremes of the
J.B. Elsner and T.H. Jagger (eds.), Hurricanes and Climate Change, 61
doi: 10.1007/978-0-387-09410-6, © Springer Science + Business Media, LLC 2009
10-11-year sunspot cycle reaches 35% in portions of the UV range. Here we examine whether we can find a solar signal in the record of hurricanes, especially those affecting the United States. The focus on U.S. hurricanes and those over the Caribbean is motivated by the reliability of records back through the 20th century and by their social and economic importance. In fact, hurricane damage to the United States has averaged greater than $35 bn (U.S.) per year since 2002.
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